1. Esophageal & Upper GI Disorders

This section covers the spectrum of esophageal and upper gastrointestinal diseases relevant to internal medicine board examinations, integrating the 2022 ACG GERD Guidelines, 2020 AGA Barrett's Esophagus Guidelines, 2020 ACG Achalasia Guidelines, and the latest evidence through 2025.

1.1 Gastroesophageal Reflux Disease (GERD)

▼ 1.1 Definition, Pathophysiology & Epidemiology

GERD is defined as troublesome symptoms or complications resulting from reflux of gastric contents into the esophagus, oropharynx, or respiratory tract (Montreal Definition, 2006 — still standard). Prevalence: ~20% in Western populations; ~10-15% in Asia (rising with westernization of diet).

Pathophysiology: Multifactorial. Core mechanism = transient lower esophageal sphincter relaxations (TLESRs) triggered by gastric distension (vagal-mediated). Contributing factors: decreased LES resting tone, hiatal hernia (impairs crural diaphragm and acid clearance), delayed gastric emptying, increased abdominal pressure (obesity, pregnancy), impaired esophageal peristalsis reducing acid clearance.

⚡ High-Yield: GERD Pathophysiology Ladder

TLESR = primary mechanism in most GERD patients (even those with normal LES tone)
Hiatal hernia → impairs acid clearance + creates "acid pocket" just below squamocolumnar junction
Obesity → ↑ intragastric pressure + ↑ TLESRs + promotes hiatal hernia
Bile reflux → contributes to non-acid or weakly-acid reflux; important in post-gastrectomy
Esophageal hypersensitivity → central sensitization in functional heartburn/reflux hypersensitivity

GERD Phenotype	Definition	Key Feature	Rome IV / Montreal Category
Erosive Esophagitis (EE)	Visible mucosal breaks on endoscopy	LA Grade A–D; positive pH-metry in majority	Esophageal GERD syndrome
Non-Erosive Reflux Disease (NERD)	Typical symptoms; normal endoscopy; abnormal acid exposure on pH-metry	Most common GERD phenotype (60-70%)	Esophageal GERD syndrome
Reflux Hypersensitivity	Normal acid exposure; symptom-reflux correlation on pH-impedance	PI-GERD: symptom index ≥50% or SAP ≥95%	Rome IV functional esophageal disorder
Functional Heartburn	Normal acid exposure; NO symptom-reflux correlation	Often anxiety/central sensitization; poor PPI response	Rome IV functional esophageal disorder

🔑 Clinical Pearl: The Lyon Consensus (2018, updated 2023) defines conclusive GERD evidence as: DeMeester score >14.72 OR acid exposure time (AET) >6% on 96-hr wireless pH or 24-hr pH-impedance. AET 4–6% = "borderline" requiring additional evidence. This framework guides therapeutic decision-making, especially before anti-reflux surgery.

▼ 1.2 Diagnosis — Clinical, Endoscopy & pH Testing

Typical symptoms: Heartburn (pyrosis), regurgitation — sufficient for empiric PPI therapy in patients without alarm features. Atypical/extraesophageal: Chronic cough, laryngitis, asthma, dental erosions, non-cardiac chest pain (NCCP). Empiric PPI trial for NCCP is reasonable (sensitivity ~80% for GERD-related NCCP).

Alarm features requiring prompt endoscopy (ABCDE): Anemia (iron-deficiency), Bleeding (hematemesis/melena), Chronic cough/dysphagia, Dysphagia/odynophagia, Evidence of weight loss (unintentional).

Diagnostic Tool	Indication	Key Parameters	Limitations
Upper endoscopy (EGD)	Alarm features; chronic GERD ≥5 yr (Barrett's screening); refractory symptoms; pre-op evaluation	LA Classification A-D; detect Barrett's, strictures, cancer	Normal in 60-70% GERD (NERD); low sensitivity for GERD per se
24-hr pH-impedance (off PPI)	Refractory GERD; atypical symptoms; pre-op evaluation; distinguish NERD from functional heartburn	AET >6% = pathologic; symptom index ≥50%; SAP ≥95%	Catheter-based; single 24-hr window; catheter intolerance
96-hr wireless pH (Bravo)	Inconclusive 24-hr study; need longer monitoring; better tolerability	AET averaged over 4 days; day-to-day variability captured	Cost; capsule attachment failure rare
Esophageal manometry (HRM)	Pre-op evaluation; exclude achalasia; atypical symptoms	Assess LES pressure, peristaltic reserve, hiatal hernia	Not a test for GERD diagnosis per se
Empiric PPI trial (8 weeks)	Typical GERD symptoms without alarm features; initial management	≥50% symptom relief supports GERD diagnosis	Response does not confirm GERD; may be placebo response

🔑 Clinical Pearl: Per ACG 2022, routine endoscopy is NOT recommended for initial management of typical GERD symptoms without alarm features. EGD is recommended for Barrett's screening in patients with chronic GERD (≥5 years) plus ≥3 risk factors: male sex, age >50, obesity (BMI >30), smoking, white race, first-degree relative with Barrett's/esophageal adenocarcinoma.

▼ 1.3 Treatment — Lifestyle, PPI, Surgery & Novel Therapies

Step 1 — Lifestyle modifications: Weight loss (most evidence for symptomatic benefit), head-of-bed elevation 6–8 inches (for nocturnal/regurgitation-predominant), avoid late meals (≥2–3 hr before sleep), reduce alcohol and high-fat meals, smoking cessation. Evidence for eliminating trigger foods (citrus, chocolate, coffee, mint) is limited but individualized.

Drug Class	Mechanism	Dose (Standard)	Evidence Level	Key Points
Omeprazole / Lansoprazole	PPI — irreversible H⁺/K⁺-ATPase inhibition on activated pumps	20 mg / 30 mg QD, 30–60 min before breakfast	First-line; Grade A	Take 30–60 min before first meal; 70% pumps activated postprandially
Esomeprazole / Pantoprazole	PPI (S-isomer / less CYP interaction)	40 mg / 40 mg QD	Grade A; pantoprazole preferred if on clopidogrel	Pantoprazole: least CYP2C19 interaction; preferred with antiplatelet therapy
Vonoprazan (P-CAB)	Potassium-competitive acid blocker — faster, more sustained acid suppression; NOT activated-pump dependent	20 mg QD (Japan/SE Asia/US FDA approved 2023)	Non-inferior to lansoprazole for EE healing; superior for LA C/D	No need to take before meal; effective regardless of CYP2C19 genotype; approved in US 2023 for EE
Famotidine (H2RA)	H2-receptor antagonist — faster onset; tolerance within 2 weeks	20–40 mg BID (OTC: 10–20 mg PRN)	Inferior to PPI for EE healing; useful for breakthrough nocturnal symptoms	Add H2RA at bedtime for nocturnal acid breakthrough on PPI; tachyphylaxis limits chronic use
Baclofen	GABA-B agonist → reduces TLESRs	5–20 mg TID	Evidence for refractory regurgitation; reduces postprandial TLESRs	CNS side effects (sedation, dizziness) limit use; useful for volume regurgitation refractory to PPI
Sucralfate	Mucosal protectant; binds bile acids	1 g QID before meals and bedtime	Pregnancy GERD (Grade B)	Drug of choice for GERD in pregnancy (safe category); limited efficacy data otherwise

Surgical / Interventional: Laparoscopic Nissen fundoplication (360°) — indicated for confirmed GERD with: (a) preference to avoid long-term PPI, (b) refractory symptoms on PPI with confirmed GERD on pH testing, (c) volume regurgitation unresponsive to PPI. Requires pre-op HRM to exclude achalasia/aperistalsis. Dysphagia (~10%) and gas-bloat syndrome are common complications. Magnetic sphincter augmentation (LINX) — ring of magnetic beads; reversible; less dysphagia than Nissen; contraindicated with MRI. Transoral incisionless fundoplication (TIF 2.0) — endoscopic; less invasive; less durable than surgical fundoplication; suitable for small hiatal hernias.

🔑 Clinical Pearl — PPI Safety: Long-term PPI use: monitor Mg²⁺ (hypomagnesemia after >1 year), B12 (malabsorption), bone density (modest fracture risk with high-dose chronic use). C. difficile risk is increased with PPI. However, benefits generally outweigh risks in guideline-appropriate indications. Do NOT discontinue PPI in Barrett's esophagus — PPI reduces risk of progression to dysplasia.

▼ 1.4 Barrett's Esophagus — Screening, Surveillance & Endoscopic Therapy

Barrett's esophagus (BE) is defined as intestinal metaplasia (IM) of the esophagus — columnar-lined esophagus ≥1 cm with goblet cells on biopsy (required in US per ACG; not required in UK BSG guidelines). BE is the only known precursor to esophageal adenocarcinoma (EAC), the most rapidly increasing GI cancer in Western countries.

Stage	Endoscopic Finding	Histology	Surveillance Interval	Management
Non-dysplastic BE (NDBE)	Salmon-colored mucosa; IM on biopsy; no dysplasia	Intestinal metaplasia, no dysplasia	3–5 yr (short-segment BE ≤3 cm → 5 yr; long-segment >3 cm → 3 yr)	PPI (reduces dysplasia risk); surveillance EGD; aspirin 81–325 mg/day if cardiovascular indication
Low-Grade Dysplasia (LGD)	Flat mucosa; architectural irregularity on biopsy	Dysplastic cells confined to crypts; confirmed by 2nd expert GI pathologist	6-monthly EGD after confirmation OR proceed to ablation	Endoscopic eradication therapy (EET) preferred — RFA reduces progression to EAC by 80% (AIM Dysplasia Trial)
High-Grade Dysplasia (HGD)	Nodular or flat mucosa; may be subtle	Full-thickness epithelial dysplasia without invasion	Treat; do NOT continue surveillance alone	EET (EMR for nodules + RFA for flat BE); esophagectomy only if EET fails or multifocal HGD not amenable to endoscopy
Intramucosal Adenocarcinoma (T1a)	Nodular or depressed lesion; EMR required for staging	Invasion into lamina propria or muscularis mucosae; lymph node risk ~2%	EET if well/mod differentiated, no lymphovascular invasion, clear margins	EMR for complete local staging → RFA for remaining BE; esophagectomy if poor differentiation or lymphovascular invasion
Submucosal Adenocarcinoma (T1b)	Nodular; depressed; EUS for staging	Invasion into submucosa; LN risk 20–25%	Surgical esophagectomy preferred; ESD in selected cases (sm1, well-differentiated)	Refer to esophageal surgery center; multidisciplinary team

⚡ Endoscopic Eradication Therapy (EET) — Key Concepts

EMR (Endoscopic Mucosal Resection) — cap-assisted suction or band ligation technique; for visible nodules/lesions; provides tissue for accurate staging (T1a vs T1b)
ESD (Endoscopic Submucosal Dissection) — en-bloc resection for larger lesions; preferred for T1b sm1; higher technical difficulty; risk of perforation ~3-5%
RFA (Radiofrequency Ablation) — AIM Dysplasia Trial 2009 (NEJM): RFA vs sham; complete eradication of HGD 81% vs 19%; LGD 90% vs 23%; prevented EAC at 3 years (1.2% vs 9.3%). Standard of care for flat dysplastic BE after focal EMR of nodules
Cryotherapy — spray or balloon cryoablation; used for refractory BE after failed RFA or circumferential RFA-resistant areas
Complete Eradication of IM (CE-IM) — the goal of EET. Post-eradication surveillance: 3 mo after CE-IM, then 6-12 mo, then annually. Recurrence risk: ~8%/year for IM; ~2%/year for dysplasia.

▼ 1.5 Achalasia — Classification, Diagnosis & Treatment

Achalasia is a primary esophageal motility disorder characterized by: (1) failure of LES relaxation (impaired integrated relaxation pressure, IRP >15 mmHg on HRM), and (2) absent peristalsis in the esophageal body. Pathophysiology: selective loss of inhibitory (NO/VIP-producing) myenteric neurons. Etiology: autoimmune (HSV-1 trigger in genetically susceptible individuals proposed). Incidence: ~1/100,000/year.

Chicago Classification v4.0 Type	HRM Pattern	Prevalence	Response to Therapy	Notes
Type I (Classic)	IRP >15 mmHg; 100% failed peristalsis; minimal pressurization	~20%	Intermediate response	Dilated esophagus; "bird-beak" on barium; late presentation
Type II (Panesophageal pressurization)	IRP >15 mmHg; ≥20% swallows with pan-esophageal pressurization ≥30 mmHg	~70%	Best response to all therapies	Most common subtype; best prognosis post-treatment
Type III (Spastic)	IRP >15 mmHg; ≥20% swallows with premature/spastic contractions (DL <4.5 s)	~10%	Poor response to dilation; POEM preferred	Chest pain prominent; POEM targets long myotomy including spastic body
EGJ Outflow Obstruction (EGJOO)	IRP >15 mmHg; preserved/weak peristalsis (not fulfilling achalasia criteria)	Variant	Variable; exclude mechanical obstruction first	May represent early/incomplete achalasia; exclude pseudoachalasia (malignancy, fundoplication)

Treatment Modality	Mechanism	Success Rate	Preference	Key Trials
Pneumatic Dilation (PD)	Mechanical disruption of LES fibers; 30/35/40 mm balloons sequentially	70-90% (3 yr); decreasing over time; repeat dilations needed	Suitable for all types; preferred in elderly/poor surgical candidates	European Achalasia Trial: PD non-inferior to LHM at 2 yr (86% vs 90%)
Laparoscopic Heller Myotomy + Partial Fundoplication (LHM)	Surgical division of LES circular muscle fibers + partial fundoplication (Dor/Toupet) to prevent GERD	85-90% (5 yr)	Standard surgical therapy; add partial fundoplication to prevent GERD	European Achalasia Trial; POEM vs LHM: ESOREACT (non-inferior)
Per-Oral Endoscopic Myotomy (POEM)	Endoscopic submucosal tunneling + myotomy of inner circular and outer longitudinal muscle fibers	90-95% (1-2 yr); durable at 5 yr ~85%	Type III preferred (long myotomy extends into body); excellent for all types	ESOREACT trial 2021 (NEJM): POEM non-inferior to LHM; higher GERD rate post-POEM (44% vs 21% on pH monitoring) — requires post-POEM PPI
Botulinum Toxin Injection	Inhibits ACh release from excitatory neurons → temporary LES relaxation	60-80% (6 months); recurrence common	Elderly/frail patients with high surgical risk; palliation	Not guideline-recommended for fit patients due to scar tissue formation complicating future myotomy

🔑 Clinical Pearl — Pseudoachalasia: Always consider pseudoachalasia (malignancy causing extrinsic LES compression — gastric cardia, lung cancer, lymphoma) in patients >60 years, rapid weight loss, short symptom duration (<1 year), or dysphagia to liquids early. CT chest/abdomen and EUS are essential before HRM-based achalasia diagnosis in this population.

▼ 1.6 Eosinophilic Esophagitis (EoE)

EoE is a chronic, immune/antigen-mediated esophageal disease characterized by: ≥15 eosinophils/HPF on esophageal biopsy + symptoms of esophageal dysfunction + exclusion of other causes. Increasing incidence; strongly associated with atopy (asthma, allergic rhinitis, eczema, food allergy). Most common cause of food bolus impaction in young adults.

Presentation: Dysphagia to solids (most common), food impaction, heartburn (PPI-unresponsive), chest pain. Children: vomiting, feeding refusal, failure to thrive.

Endoscopic findings (EREFS score): Rings (trachealization), Exudates (white plaques/furrows), Furrows, Edema (loss of vascular pattern), Strictures — mnemonic REEFS or EREFS.

⚡ EoE Treatment Ladder (2023 AGA/ACG)

High-dose PPI (omeprazole 40 mg BID × 8 weeks) — first-line; ~30-40% histologic remission (PPI-responsive EoE now considered within EoE spectrum, not excluded by definition)
Swallowed topical corticosteroids — budesonide oral suspension (approved 2022 by FDA as Jorveza/EOHELIA) or fluticasone propionate swallowed (off-label); 50-70% histologic remission; adrenal suppression risk minimal
Dupilumab (anti-IL-4Rα) — FDA approved May 2022 for EoE ≥12 years; first biologic for EoE; 59% histologic remission (PART 1+2 trial, NEJM 2022); monthly injections; preferred for biologic-eligible patients
Dietary elimination — 6-food elimination diet (milk, wheat, egg, soy, nuts, seafood) → 70-80% remission; step-down 2-food (milk, wheat) or 1-food (milk) strategies increasingly used for practicality
Esophageal dilation — for symptomatic strictures/rings; treats dysphagia but does NOT treat inflammation; perform after anti-inflammatory therapy for refractory dysphagia

▼ 1.7 Approach to Dysphagia — Algorithm for Internists

Dysphagia = difficulty swallowing. Classified as oropharyngeal (transfer dysphagia — difficulty initiating swallow; coughing/choking; nasal regurgitation) vs esophageal (sensation of food "sticking" after swallowing, ≥5 seconds from swallow initiation).

Clinical Pattern	Most Likely Diagnoses	Key Investigation
Solids only → progressive; weight loss; age >50	Esophageal carcinoma (SCC or adenocarcinoma), Peptic stricture	EGD + biopsy (urgent); barium swallow if EGD not immediately available
Solids only → intermittent; younger patient; no weight loss	Schatzki ring, Eosinophilic esophagitis, Esophageal web	EGD; biopsies (4 quadrant proximal + mid + distal esophagus for EoE)
Solids AND liquids → progressive	Achalasia, Diffuse esophageal spasm, Esophageal motility disorder	Barium swallow (bird-beak, tertiary contractions) → HRM (esophageal manometry)
Solids AND liquids; oropharyngeal symptoms; neurologic signs	Stroke, Parkinson's, MG, ALS, Zenker's diverticulum	Bedside swallowing assessment → VFSS (video fluoroscopic swallowing study) or FEES; neurologic workup
Odynophagia (painful swallowing)	Infectious esophagitis (Candida, HSV, CMV), Pill esophagitis, EoE	EGD + biopsies; HIV test if immunocompromised

🔑 Clinical Pearl — Infectious Esophagitis: In immunocompromised patients (HIV, transplant, steroids), Candida esophagitis (white plaques — most common) warrants empiric fluconazole without endoscopy if classic presentation + CD4 <100; EGD if no response in 3-5 days or if odynophagia prominent (suggests HSV/CMV). HSV: vesicles/ulcers (biopsy: intranuclear inclusions); CMV: linear ulcers (biopsy: owl-eye inclusions); treat with acyclovir and ganciclovir respectively.

📚 Key References — Esophageal & Upper GI

ACG 2022 GERD Guidelines — Gyawali CP et al. Am J Gastroenterol 2023;118(7):1130-1166. Lyon Consensus 2.0 framework.
AGA 2022 Barrett's Esophagus Guidelines — Shaheen NJ et al. Gastroenterology 2022;162(7):2012-2028. Surveillance intervals and EET recommendations.
AIM Dysplasia Trial — Shaheen NJ et al. NEJM 2009;360:2277-2288. RFA for LGD/HGD — landmark EET trial.
ACG 2020 Achalasia Guidelines — Vaezi MF et al. Am J Gastroenterol 2020;115(9):1393-1411.
ESOREACT Trial — Ponds FA et al. NEJM 2021;384:929-940. POEM vs Heller myotomy — non-inferiority.
Dupilumab EoE (PART 1+2) — Dellon ES et al. NEJM 2022;387:2327-2340. First approved biologic for EoE.

▼📝 Practice Questions — Esophageal & Upper GI

Q1. A 62-year-old male with 10 years of GERD and obesity (BMI 32) undergoes screening EGD. A 4 cm salmon-pink segment is found at the GEJ with biopsy showing intestinal metaplasia, no dysplasia. What is the correct surveillance interval and management?

Answer: EGD surveillance every 3 years + PPI continuation

This patient has long-segment non-dysplastic Barrett's esophagus (NDBE, >3 cm). Per AGA 2022 guidelines, NDBE with segment ≥3 cm → surveillance every 3 years (short-segment <3 cm → every 5 years). PPI should be continued — it reduces the risk of progression to dysplasia. This patient also has ≥3 Barrett's risk factors (male, age >50, obesity, chronic GERD) — all warranting screening. Do NOT add aspirin solely for Barrett's without cardiovascular indication per current guidelines.

Q2. A 38-year-old woman presents with 6 months of dysphagia to solids AND liquids, regurgitation of undigested food, and 5 kg weight loss. Barium swallow shows a "bird-beak" narrowing at the distal esophagus. What is the investigation to confirm the diagnosis and the preferred treatment?

Answer: High-resolution manometry (HRM) → POEM (preferred) or Heller myotomy

The clinical and radiological picture is classic for achalasia (dysphagia to solids AND liquids, bird-beak on barium). HRM is required to confirm (IRP >15 mmHg + absent peristalsis) and classify type (I, II, or III). Treatment: POEM and laparoscopic Heller myotomy are both first-line with comparable outcomes (ESOREACT 2021). POEM is particularly preferred for Type III (spastic). Always rule out pseudoachalasia with CT/EGD (malignancy at GEJ). Botulinum toxin injection is reserved for elderly/frail patients only — not first choice here.

Q3. A 25-year-old atopic male (asthma, eczema) presents with episodic food impaction requiring emergency EGD 3 times over 2 years. EGD shows rings and furrows in the esophagus. Biopsies show 25 eosinophils/HPF. He is currently on omeprazole 20 mg QD. What is the next step?

Answer: Escalate to high-dose PPI (omeprazole 40 mg BID) OR swallowed topical corticosteroids (budesonide oral suspension) OR dupilumab

This is Eosinophilic Esophagitis (EoE) — ≥15 eos/HPF + esophageal symptoms + compatible endoscopy in an atopic patient. Current low-dose PPI is inadequate — escalate to high-dose PPI (40 mg BID × 8 weeks) as first step per AGA 2020. If insufficient response: swallowed topical corticosteroids (budesonide oral suspension FDA-approved 2022) or dupilumab (FDA-approved 2022 for EoE ≥12 years). Low-FODMAP or 6-food elimination diet is also an option if patient willing. Esophageal dilation treats dysphagia but does not address inflammation — add after anti-inflammatory therapy.

2. Peptic Ulcer Disease & H. pylori

Peptic ulcer disease (PUD) encompasses gastric and duodenal ulcers caused by an imbalance between aggressive factors (acid, pepsin, H. pylori, NSAIDs) and mucosal defense. This section integrates the 2017 ACG H. pylori Guidelines, 2022 ACG NSAID/PUD Guidelines, and the Maastricht VI/Florence Consensus (2022).

▼2.1 Epidemiology & Etiology

Lifetime prevalence of PUD ~10% in Western populations. H. pylori infection causes 70% of gastric and ~90% of duodenal ulcers globally. NSAID/aspirin use accounts for most remaining cases (up to 25%). Rare causes: Zollinger-Ellison syndrome (ZES), stress ulcers (ICU), Crohn's disease, CMV, cocaine use.

Cause	Mechanism	Distinguishing Feature	Key Management
H. pylori	Urease → NH₃ (neutralizes acid locally); CagA, VacA virulence factors → disrupts tight junctions, induces apoptosis; ↑ gastrin, ↓ somatostatin → ↑ acid	Most duodenal ulcers; antral gastritis; gastric MALT lymphoma	Test and treat; eradication heals ulcer in 90%
NSAIDs / Aspirin	COX-1 inhibition → ↓ prostaglandin E₂ → ↓ mucus, ↓ bicarbonate, ↓ mucosal blood flow; direct topical epithelial injury	Gastric ulcers more common than duodenal; often silent until bleeding	Stop NSAID if possible; PPI co-therapy; switch to celecoxib if NSAID required
Zollinger-Ellison (Gastrinoma)	Autonomous gastrin secretion → massive acid hypersecretion; >10 mEq/L basal acid output	Multiple ulcers; distal duodenal/jejunal ulcers; diarrhea; refractory to standard therapy; MEN-1 association	High-dose PPI; surgical resection for sporadic; somatostatin analogues for MEN-1
Stress ulcers (Curling/Cushing)	Mucosal ischemia (Curling's — burns); vagal-mediated acid hypersecretion (Cushing's — head injury)	ICU patients; mechanical ventilation; coagulopathy	PPI/H2RA prophylaxis in high-risk ICU patients

▼2.2 H. pylori — Diagnosis & Eradication

Helicobacter pylori infects ~50% of the world population (>80% in developing countries including Thailand). Transmission: fecal-oral route. Associated with: peptic ulcers, gastric adenocarcinoma (class I carcinogen), gastric MALT lymphoma, iron deficiency anemia, ITP.

Test	Sensitivity	Specificity	Clinical Notes
Urea Breath Test (UBT — ¹³C or ¹⁴C)	94-96%	96-98%	Non-invasive; gold standard for test-and-treat and post-eradication confirmation. Stop PPI 2 weeks before; antibiotics 4 weeks before
Stool Antigen Test (HpSA)	92-95%	94-97%	Preferred in areas where UBT unavailable; monoclonal preferred over polyclonal. Same PPI/antibiotic washout as UBT. Used for post-eradication testing.
Serology (IgG ELISA)	80-90%	75-85%	Cannot distinguish active from past infection; NOT recommended for post-eradication testing. Acceptable only in low-prevalence settings for initial test-and-treat strategy.
Rapid Urease Test (RUT — CLO test)	88-95%	95-99%	Invasive (requires EGD); biopsy from antrum and corpus. False negative if recent PPI use, recent antibiotic use, or bleeding (blood inhibits urease).
Histology (Giemsa/Warthin-Starry stain)	93-96%	97-99%	Invasive; also assesses gastritis grade/activity (OLGA/OLGIM staging for atrophy/IM); can identify cagA status.
Culture with Sensitivity	80-90%	100%	Gold standard for antibiotic resistance; slow growth (5-7 days); reserve for failed 2nd-line therapy or high clarithromycin resistance areas.

⚡ H. pylori Eradication Regimens — Maastricht VI / ACG 2017

Clarithromycin resistance rate determines regimen choice: If local clarithromycin resistance >15% → avoid clarithromycin-based triple therapy
Bismuth Quadruple Therapy (BQT) — PPI + bismuth + metronidazole + tetracycline × 14 days. Eradication ~90%; first-line in high-resistance areas (Asia, Eastern Europe, Middle East). Also available as Pylera® (single capsule).
Concomitant Therapy (non-bismuth quadruple) — PPI + clarithromycin + amoxicillin + metronidazole × 14 days. Eradication ~90%; overcomes both clarithromycin and metronidazole resistance by dual action.
Vonoprazan-based Dual Therapy — Vonoprazan 20 mg BID + amoxicillin 1 g TID × 14 days. FDA approved 2022; eradication 84% (naïve) vs 79% (triple therapy); excellent for clarithromycin-resistant strains.
Sequential Therapy — PPI + amoxicillin × 5 days → then PPI + clarithromycin + metronidazole × 5 days. Total 10 days. Inferior to BQT or concomitant in most studies — not preferred.
Always confirm eradication with UBT or stool antigen ≥4 weeks after completing therapy and ≥2 weeks after stopping PPI.
Rescue regimens: After failed 1st-line: Levofloxacin-based triple (if not used before) OR Rifabutin-based triple (amoxicillin + rifabutin + PPI) as 3rd-line.

🔑 Clinical Pearl — Gastric MALT Lymphoma: Low-grade gastric MALT (mucosa-associated lymphoid tissue) lymphoma is driven by H. pylori-stimulated T-cell activation of neoplastic B cells. H. pylori eradication alone achieves complete remission in ~75% of low-grade, localized MALT lymphoma (t(11;18)(q21;q21) negative tumors respond best). Follow with repeat EGD + biopsies every 3 months until remission. High-grade transformation or t(11;18) requires radiation or rituximab-based chemo.

▼2.3 PUD Management, NSAID Gastropathy & ZES

Uncomplicated PUD: PPI for 4–8 weeks (duodenal 4 weeks; gastric 8 weeks). H. pylori eradication if positive. Confirm healing of gastric ulcers endoscopically at 8–12 weeks (10–20% may harbour cancer). NSAIDs: discontinue if possible; if ongoing required, use celecoxib (COX-2 selective) + PPI (most gastroprotective combination per CONDOR and GI-REASONS trials).

NSAID GI Risk Category	Definition	Strategy
Low GI risk	No risk factors (age <65, no prior PUD, no anticoagulant/steroid use)	Non-selective NSAID without PPI
Moderate GI risk	1–2 risk factors	COX-2 selective NSAID (celecoxib) OR non-selective NSAID + PPI
High GI risk	Prior ulcer/bleeding history, or ≥3 risk factors, or on anticoagulants	COX-2 selective + PPI; if possible avoid NSAIDs altogether

Zollinger-Ellison Syndrome (ZES): Diagnosis confirmed by fasting serum gastrin >1000 pg/mL (strongly suggestive) OR >10× ULN with gastric pH <2 (secretin stimulation test: rise ≥120 pg/mL). Gastrinoma triangle location (75% within: cystic duct-CBD junction, 2nd-3rd duodenal junction, neck-body pancreas junction). MEN-1 association (30%): check PTH, prolactin, IGF-1. Imaging: SRS (somatostatin receptor scintigraphy) or ⁶⁸Ga-DOTATATE PET/CT (superior sensitivity). Treatment: high-dose PPI (omeprazole 60–120 mg/day); surgical resection for sporadic, localized disease.

🔑 Clinical Pearl — False Elevated Gastrin: PPI use is the most common cause of hypergastrinemia (G-cell hyperplasia due to elevated pH). Always stop PPI ≥1–2 weeks before measuring fasting gastrin for ZES workup. Other causes: atrophic gastritis (pernicious anemia), renal failure, H. pylori gastritis. In ZES, gastric pH is low (<2) despite elevated gastrin — unlike atrophic gastritis where pH is high (>3).

📚 Key References — PUD & H. pylori

ACG 2017 H. pylori Guidelines — Chey WD et al. Am J Gastroenterol 2017;112:212-239.
Maastricht VI/Florence Consensus 2022 — Malfertheiner P et al. Gut 2022;71:1724-1762. Most current European H. pylori management guidelines.
CONDOR Trial — Chan FK et al. Lancet 2010;376:173-179. Celecoxib vs diclofenac+omeprazole in GI high-risk NSAID users.
Vonoprazan Dual Therapy FDA — Chey WD et al. NEJM 2022;386:1981-1991. (PHALCON-HP trial).

▼📝 Practice Questions — PUD & H. pylori

Q1. A 45-year-old woman with known GERD is found to have a fasting serum gastrin of 450 pg/mL (ULN 100 pg/mL) on routine labs. She is currently taking omeprazole 40 mg BID. What is the most appropriate next step?

Answer: Stop PPI ≥2 weeks, then repeat fasting gastrin with gastric pH

PPI use is the most common cause of hypergastrinemia. Omeprazole raises gastric pH → G-cell hyperplasia → secondary hypergastrinemia. This is NOT Zollinger-Ellison syndrome until proven otherwise. The correct approach: stop PPI for ≥1–2 weeks, then re-measure fasting gastrin AND gastric pH simultaneously. ZES diagnosis requires: gastrin >1000 pg/mL (or >10×ULN) WITH gastric pH <2 (confirms autonomous acid secretion — low pH despite high gastrin). If off PPI and gastrin normalizes → PPI-induced. Other causes: H. pylori gastritis, atrophic gastritis (pH high), renal failure.

Q2. A 52-year-old man undergoes EGD for dyspepsia. A 2 cm gastric ulcer is found. Biopsy shows intestinal metaplasia + H. pylori infection. He is treated with bismuth quadruple therapy × 14 days. When and how should eradication be confirmed?

Answer: UBT or stool antigen test ≥4 weeks after completing therapy AND ≥2 weeks after stopping PPI

Post-eradication testing is mandatory for: all gastric ulcers, duodenal ulcers, MALT lymphoma, and is recommended for all treated patients. UBT (urea breath test) or stool antigen (HpSA, monoclonal) are the preferred non-invasive tests. Critical timing: wait ≥4 weeks after antibiotics AND ≥2 weeks after stopping PPI (PPIs suppress H. pylori, causing false-negative results). Serology should NOT be used for post-eradication testing (IgG remains elevated for months-years after eradication). For this gastric ulcer: repeat EGD at 8–12 weeks is ALSO needed to confirm healing and exclude malignancy — regardless of H. pylori status.

3. Inflammatory Bowel Disease (IBD)

IBD encompasses Crohn's disease (CD) and ulcerative colitis (UC) — chronic, relapsing-remitting immune-mediated inflammatory conditions of the GI tract. Incidence rising globally including Thailand/SE Asia. This section integrates the 2019 ACG UC Guidelines, 2018 ACG CD Guidelines, ECCO 2023 Guidelines, and landmark biologics trial data.

▼3.1 UC vs Crohn's — Distinguishing Features

Feature	Ulcerative Colitis	Crohn's Disease
Distribution	Rectum (always) → proximal; continuous involvement	Any GI tract (mouth to anus); skip lesions; terminal ileum (most common)
Depth of inflammation	Mucosal only (superficial)	Transmural (all layers) → fistulas, abscesses, strictures
Rectal involvement	Always (except rectal-sparing with topical therapy)	Rectal sparing in 50% of ileocolonic CD
Granulomas on biopsy	Absent (crypt abscesses, goblet cell depletion)	Non-caseating granulomas in 30-60%
Perianal disease	Absent	Fistulas, abscesses, skin tags in 30-40%
Bloody diarrhea	Classic presenting symptom	Less common (unless colonic CD)
Complications	Toxic megacolon, CRC risk (long-standing), PSC association (70% of PSC patients have UC)	Strictures, fistulas, abscesses, SBO, B12 deficiency (terminal ileal disease), oxalate kidney stones, gallstones
Surgical cure	Yes — total proctocolectomy curative	No — recurrence after resection common; surgery is palliative
Smoking effect	Smoking is protective (nicotine ↑ mucosal integrity) — onset often follows smoking cessation	Smoking is a risk factor for CD and worsens disease course

Extraintestinal Manifestations (EIMs) — parallel vs independent disease activity:

EIM	Parallel Activity	Independent Activity
Peripheral arthritis type 1 (large joints, migratory, <5 joints)	Yes — treat IBD	—
Erythema nodosum	Yes — treat IBD	—
Episcleritis / Uveitis	Episcleritis parallel; Uveitis INDEPENDENT	Uveitis — ophthalmology referral regardless of IBD activity; can cause blindness if untreated
Pyoderma gangrenosum	Usually independent	Yes — intralesional/systemic steroids; cyclosporine
Ankylosing spondylitis / sacroiliitis	Independent	Yes — NSAIDs (use with caution — may worsen IBD); anti-TNF effective for both
PSC (Primary Sclerosing Cholangitis)	Independent — may progress even after colectomy	Yes — ursodiol; ERCP for dominant strictures; liver transplant

▼3.2 Ulcerative Colitis — Assessment & Treatment

Disease activity scoring (Mayo Score): Stool frequency (0-3), rectal bleeding (0-3), endoscopic appearance (0-3), physician assessment (0-3). Total 0-12: remission ≤2; mild 3-5; moderate 6-10; severe ≥11. Truelove-Witts criteria for severe UC: ≥6 bloody stools/day + ≥1 systemic sign (HR >90, T >37.8°C, Hb <10.5, ESR >30). Severe UC = medical emergency.

Severity / Extent	First-Line Therapy	Maintenance	Notes
Mild-moderate proctitis (E1)	Mesalamine rectal suppository 1 g QHS	Same; tapering to every other night acceptable	Topical > oral for proctitis; combination topical + oral superior for any extent
Mild-moderate left-sided (E2)	Mesalamine enema 4 g QHS + oral mesalamine 2-4.8 g/day	Oral mesalamine 2 g/day minimum	MMX mesalamine (Lialda) 4.8 g QD for once-daily dosing
Mild-moderate extensive (E3/pancolitis)	Oral mesalamine 4-4.8 g/day ± rectal topical; if inadequate: oral prednisolone 40 mg/day × 4-6 weeks taper	Mesalamine; if steroid-dependent: thiopurine (azathioprine 2-2.5 mg/kg) or biologic	Steroid-sparing therapy essential for steroid-dependent/refractory disease
Moderate-severe extensive	Oral prednisolone 40-60 mg/day; if inadequate → biologic therapy	Biologic (infliximab, vedolizumab, ustekinumab) ± thiopurine	Avoid thiopurine monotherapy for moderate-severe UC; combination IFX+AZA superior (UC-SUCCESS trial)
Acute severe UC (Truelove-Witts)	IV methylprednisolone 60 mg/day (or hydrocortisone 100 mg QID); bowel rest optional; nutrition support; VTE prophylaxis	If no response at 3-5 days: rescue therapy	Surgical consult on admission; daily abdominal X-ray to exclude toxic megacolon
Acute severe UC — rescue	IV cyclosporine 2 mg/kg/day OR IV infliximab 5 mg/kg (accelerated induction for acute severe: 0, 3-5 days, 14 days)	Bridge to maintenance biologic or colectomy	CYSIF trial: cyclosporine = infliximab for acute severe UC; sequential therapy (cyclosporine → infliximab) increases serious infection risk

⚡ IBD Biologics — Mechanism & Positioning (2025)

Infliximab (anti-TNF chimeric) + Adalimumab (anti-TNF human) — Effective UC and CD; combination with thiopurine ↓ immunogenicity; check TB, HBV before starting; risk of serious infections, lymphoma, demyelination
Vedolizumab (anti-α₄β₇ integrin) — Gut-selective; blocks lymphocyte trafficking to GI tract; excellent safety profile (minimal systemic immunosuppression); approved UC + CD; preferred in elderly, patients with history of infections/malignancy; slower onset than anti-TNF for CD
Ustekinumab (anti-IL-12/23, p40 subunit) — IV induction then SC maintenance; approved UC + CD; good safety profile; useful for patients who failed anti-TNF
Risankizumab (anti-IL-23, p19 subunit) — Approved CD (2022) and UC (2023); superior to ustekinumab in CD (SEQUENCE trial 2023, NEJM: 58% vs 39% clinical remission at 24 weeks)
Ozanimod (S1P receptor modulator) — Oral; approved UC; keeps lymphocytes in lymph nodes; cardiac screening required (bradycardia); no live vaccines within 3 months
Tofacitinib / Upadacitinib (JAK inhibitors) — Oral; fast-acting; tofacitinib approved UC; upadacitinib approved UC + CD; boxed warning: MACE, thromboembolism (tofacitinib — ORAL Surveillance trial), malignancy; avoid in patients >65, smokers, cardiovascular history; reactivate VZV (give shingles vaccine before starting)

▼3.3 Crohn's Disease — Phenotype, Assessment & Treatment

Montreal Classification of CD: Age at diagnosis (A1 ≤16 yr, A2 17-40 yr, A3 >40 yr), Location (L1 terminal ileum, L2 colonic, L3 ileocolonic, L4 upper GI), Behavior (B1 inflammatory/non-stricturing non-penetrating, B2 stricturing, B3 penetrating, +p perianal modifier).

Disease activity — HBI (Harvey-Bradshaw Index) or CDAI: Remission = CDAI <150; moderate 220-450; severe >450.

CD Phenotype	Preferred Therapy	Key Consideration
Mild ileocecal CD (L1)	Budesonide 9 mg/day × 8-12 weeks (topically active; 90% first-pass hepatic extraction → minimal systemic side effects)	Not effective for colonic or proximal small bowel disease; no maintenance role
Moderate-severe luminal CD	Anti-TNF (infliximab/adalimumab) ± azathioprine — combination superior (SONIC trial: AZA+IFX > IFX alone); OR ustekinumab; OR risankizumab	Early biologic therapy ("top-down") superior to step-up in preventing structural damage; high-risk features: age <30, perianal, deep ulcers, upper GI → consider early biologics
Stricturing CD (B2)	Anti-inflammatory therapy for inflammatory component; endoscopic balloon dilation for short (<5 cm) fibrous strictures; surgery for long/multiple/refractory strictures	Distinguish inflammatory (responds to biologics) vs fibrotic stricture (surgery/dilation); MRI enterography identifies transmural inflammation
Penetrating CD — abscess (B3)	CT-guided or surgical drainage of abscess; antibiotics (ciprofloxacin + metronidazole); delay biologics until abscess resolved (risk of sepsis with immunosuppression)	Anti-TNF indicated after source control; do NOT start biologics with undrained abscess
Perianal CD (+p)	Examine under anesthesia (EUA) + seton placement for complex fistulas; infliximab induction for fistula healing (ACCENT II trial: 46% complete fistula closure); adalimumab also effective; MRI pelvis for complete mapping	Darvadstrocel (MSC therapy) — approved in Europe for refractory complex perianal fistula + remission on biologic (ADMIRE-CD trial)
Post-surgical CD prophylaxis	After ileocecal resection: high risk (smoking, penetrating, perianal, >1 prior resection) → anti-TNF; moderate risk → thiopurine; Rutgeerts score at 6 months post-op colonoscopy guides therapy	Rutgeerts i2–i4 = endoscopic recurrence → step up therapy

▼3.4 IBD Surveillance, Dysplasia & Colectomy Indications

Colorectal cancer (CRC) risk in UC: Cumulative risk ~2% at 10 years, ~8% at 20 years, ~18% at 30 years (colitis-associated CRC — CA-CRC). Risk factors: extensive colitis (pancolitis), long disease duration (>8 years), concurrent PSC (highest risk — annual colonoscopy from diagnosis), pseudopolyps, family history of CRC, active inflammation.

Surveillance colonoscopy: Begin 8 years after onset of pancolitis or left-sided colitis; every 1–3 years depending on risk (SCENIC guidelines). Chromoendoscopy (dye-spray with 0.1% indigo carmine or methylene blue) preferred over white-light endoscopy for dysplasia detection. Advanced imaging: virtual chromoendoscopy (NBI, FICE) acceptable alternative.

Absolute indications for colectomy in UC: Refractory severe UC not responding to rescue therapy (cyclosporine/infliximab) at 7 days, toxic megacolon not resolving with 24–72 hours medical therapy, perforation, uncontrolled hemorrhage, HGD/cancer on surveillance.

🔑 Clinical Pearl — Toxic Megacolon: Defined as non-obstructive colonic dilation >6 cm on plain film + systemic toxicity (T >38°C, HR >120, WBC >10.5, anemia). Triggers: electrolyte imbalance (hypokalemia), opioids/antidiarrheals, colonoscopy during severe flare. Management: NPO, NG decompression, IV steroids, broad-spectrum antibiotics, surgical consult. Failure to improve in 24–72 hours → emergency colectomy.

📚 Key References — IBD

ACG UC Guidelines 2019 — Rubin DT et al. Am J Gastroenterol 2019;114(3):384-413.
ACG CD Guidelines 2018 — Lichtenstein GR et al. Am J Gastroenterol 2018;113(4):481-517.
SONIC Trial — Colombel JF et al. NEJM 2010;362:1383-1395. Combination IFX+AZA superior to monotherapy in CD.
SEQUENCE Trial 2023 — Ferrante M et al. NEJM 2023;388:1780-1791. Risankizumab vs ustekinumab in CD.
CYSIF Trial — Laharie D et al. Lancet 2012;380:1909-1915. Cyclosporine = infliximab for acute severe UC.
ORAL Surveillance — Ytterberg SR et al. NEJM 2022;386:316-326. Tofacitinib cardiovascular/malignancy risk in RA (class effect caution).

▼📝 Practice Questions — IBD

Q1. A 28-year-old man with 5-year history of ulcerative colitis (pancolitis) presents with 12 bloody stools/day, HR 108, temperature 38.4°C, Hb 9.2 g/dL, WBC 14,000. He is started on IV methylprednisolone 60 mg/day. At day 4, he still has 9 bloody stools/day. What is the most appropriate next step?

Answer: Rescue therapy — IV infliximab (accelerated dosing) OR IV cyclosporine 2 mg/kg/day

This patient has acute severe ulcerative colitis (ASUC) by Truelove-Witts criteria (≥6 bloody stools/day + systemic signs). After 3–5 days of IV steroids without adequate response (Oxford criteria for steroid failure: >8 stools on day 3 OR 3–8 stools + CRP >45 mg/L) → rescue therapy is indicated. Both IV cyclosporine (2 mg/kg/day) and IV infliximab (5 mg/kg accelerated: days 0, 3-5, 14) are equally effective (CYSIF trial). Choice depends on institutional expertise, prior immunosuppressant use, and patient factors. Sequential therapy (cyclosporine → infliximab) is dangerous — avoid. Surgical consult should be obtained simultaneously. Daily abdominal X-ray to exclude toxic megacolon (>6 cm transverse colon diameter).

Q2. A 35-year-old woman with Crohn's disease (ileocolonic, fistulizing) develops a new perianal fistula with fluctuant perineal swelling and fever. MRI pelvis shows a 4 cm horseshoe abscess. What is the correct management sequence?

Answer: Surgical drainage (EUA + seton placement) + antibiotics FIRST → then infliximab after source control

In Crohn's perianal disease with abscess: NEVER start biologics (infliximab) with an undrained abscess — risk of sepsis and abscess extension under immunosuppression. Correct sequence: (1) Examination under anesthesia (EUA) + surgical drainage of abscess + seton placement for fistula complex to maintain drainage, (2) Antibiotics (ciprofloxacin + metronidazole) to treat acute infection, (3) After abscess resolves (usually 2–6 weeks) → start infliximab for long-term fistula healing (ACCENT II: 46% complete closure). MRI pelvis is essential for complete perianal fistula mapping before and after treatment.

Q3. A 42-year-old woman with UC (pancolitis × 14 years) and concurrent PSC (diagnosed 8 years ago) undergoes surveillance colonoscopy. A flat 8 mm lesion is found in the sigmoid colon on chromoendoscopy. Biopsy shows low-grade dysplasia. What is the management?

Answer: Endoscopic resection (EMR/polypectomy) if completely resectable → repeat colonoscopy in 3–6 months; colectomy if not completely resectable

PSC+UC carries dramatically elevated CRC risk — annual colonoscopy from time of PSC/IBD diagnosis (not the standard 8-year rule). Dysplasia management in IBD: (1) Visible, discrete, resectable dysplastic lesion → EMR/polypectomy; confirm complete resection; surveillance at 3–6 months, then annual. (2) Invisible/multifocal HGD OR LGD not endoscopically resectable → colectomy. (3) Confirmed HGD anywhere → strong recommendation for colectomy discussion. The presence of PSC does NOT automatically mandate colectomy for LGD — but it escalates surveillance intensity. Chromoendoscopy (per SCENIC guidelines) should be used for IBD surveillance.

4. Functional GI Disorders & IBS

Functional gastrointestinal disorders (FGIDs) — now termed Disorders of Gut-Brain Interaction (DGBI) per Rome IV (2016) — are characterized by GI symptoms without structural or biochemical abnormalities on routine testing. They represent a gut-brain axis dysfunction involving altered gut motility, visceral hypersensitivity, altered mucosal immune function, altered gut microbiota, and central sensitization.

▼4.1 IBS — Rome IV Criteria & Subtypes

Rome IV IBS Criteria (2016): Recurrent abdominal pain ≥1 day/week on average in the last 3 months, associated with ≥2 of: (1) related to defecation, (2) associated with change in stool frequency, (3) associated with change in stool form/appearance. Criteria fulfilled for last 3 months with symptom onset ≥6 months before diagnosis.

IBS Subtype	Bristol Stool Form	Prevalence	First-Line Therapy
IBS-C (Constipation-predominant)	>25% type 1-2; <25% type 6-7	~30% of IBS	Fiber (psyllium), osmotic laxatives; linaclotide, plecanatide, tegaserod (limited use)
IBS-D (Diarrhea-predominant)	>25% type 6-7; <25% type 1-2	~30% of IBS	Low-FODMAP diet; loperamide; rifaximin; eluxadoline; TCAs; bile acid sequestrants if bile acid malabsorption
IBS-M (Mixed)	Both >25% types 1-2 AND >25% types 6-7	~20% of IBS	Address predominant symptom; antispasmodics; mebeverine; peppermint oil
IBS-U (Unclassified)	Does not fit C, D, or M criteria	~20% of IBS	Symptomatic; consider neuromodulators (TCAs, SNRIs)

Alarm features (ALARM criteria) — investigate to exclude organic disease: Age >50 at onset, anemia (iron-deficiency), Loss of weight (unexplained), Altered bowel habit >6 weeks, Rectal bleeding, Mass on examination.

Diagnostic approach (AGA 2021): CBC, CRP, fecal calprotectin (FC) to exclude IBD (FC <50 μg/g supports DGBI diagnosis); celiac serology (anti-TTG IgA) in IBS-D. Colonoscopy only if alarm features or screening age. Routine colonoscopy NOT needed for uncomplicated IBS diagnosis meeting Rome IV criteria.

🔑 Clinical Pearl — Post-Infectious IBS (PI-IBS): IBS symptoms developing after an acute bout of infectious gastroenteritis (bacterial, viral, parasitic). Prevalence ~10-15% of GI infections. Risk factors: female sex, prolonged acute illness, psychological factors (anxiety, depression) at time of infection. Pathophysiology: persistent low-grade mucosal inflammation, increased intestinal permeability, altered microbiota, serotonin system dysregulation. Important to recognize — validates patient's experience and guides treatment (same as IBS-D).

▼4.2 IBS Treatment — Diet, Drugs & Neuromodulators

Drug	Mechanism	Indication	Evidence	Key Points
Linaclotide 290 mcg QD	GC-C agonist → ↑ cGMP → ↑ Cl⁻/HCO₃⁻ secretion + ↓ visceral afferents	IBS-C	FDA approved; ↑ complete SBM/week vs placebo; NNT ~6	Diarrhea dose-limiting; take 30 min before breakfast; 72 mcg dose for chronic constipation
Plecanatide 3 mg QD	GC-C agonist (pH-dependent); similar to linaclotide	IBS-C, CIC	FDA approved 2018 for IBS-C; similar efficacy to linaclotide	pH-sensitive activation in proximal duodenum; theoretical ↓ proximal diarrhea
Tenapanor 50 mg BID	NHE3 inhibitor → blocks Na⁺ absorption in small intestine/colon → ↑ luminal fluid, ↓ phosphate absorption	IBS-C	FDA approved 2019; also approved for hyperphosphatemia in CKD	Useful in IBS-C with renal disease (dual benefit); diarrhea main side effect
Rifaximin 550 mg TID × 14 days	Non-absorbable antibiotic; ↓ small intestinal bacterial fermentation; ↓ methane/hydrogen production	IBS-D (non-constipation IBS)	TARGET 1+2 trials: 40% vs 31% adequate relief; can repeat if relapse (TARGET 3)	Targets intestinal microbiome without systemic absorption; low C. diff risk; repeat courses safe
Eluxadoline 100 mg BID	Mixed μ/κ-opioid agonist + δ-opioid antagonist → ↓ motility + ↓ visceral pain without constipation rebound	IBS-D	FDA approved; NNT 9-11 for composite response	Contraindicated: no gallbladder (post-cholecystectomy → risk of sphincter of Oddi spasm), prior pancreatitis, heavy alcohol use (≥3 drinks/day)
Amitriptyline / Nortriptyline 10-50 mg QHS	TCA — ↓ visceral hypersensitivity; ↓ GI transit; neuromodulatory (central + peripheral)	IBS-D, pain-predominant IBS	Meta-analyses: significant reduction in abdominal pain vs placebo; NNT ~4	Low-dose regime; anticholinergic effects useful for IBS-D (↓ motility); start 10 mg; titrate; bedtime dosing ↓ daytime sedation
Peppermint Oil (enteric-coated)	L-menthol → Ca²⁺ channel blocker → smooth muscle relaxation → antispasmodic	Abdominal pain/cramps in IBS	Meta-analysis: superior to placebo for global IBS symptoms; NNT ~4	Enteric-coated capsules prevent GERD; safe; OTC availability; good first-line for pain/bloating

Low-FODMAP Diet: Restricts Fermentable Oligo-, Di-, Mono-saccharides and Polyols. 50-80% symptom improvement; requires dietitian guidance; 3-phase approach: elimination (4-6 weeks) → reintroduction → personalization. Does NOT address underlying gut-brain axis; not recommended long-term without reintroduction due to microbiome impact.

Gut-Directed Hypnotherapy / CBT: Strong evidence for IBS (NNT ~3 for CBT); addresses brain-gut dysregulation; durable at 12 months; recommended in Rome IV for refractory IBS.

▼4.3 Functional Dyspepsia & Gastroparesis

Rome IV Functional Dyspepsia (FD): ≥1 of: postprandial fullness (bothersome), early satiation, epigastric pain/burning; symptoms present for last 3 months with onset ≥6 months; no structural cause on EGD.

FD Subtypes: (1) Postprandial Distress Syndrome (PDS) — meal-induced fullness/satiation; impaired gastric accommodation; (2) Epigastric Pain Syndrome (EPS) — pain/burning not related to meals; more acid-related.

Treatment	Target	Evidence
H. pylori eradication (test-and-treat)	All FD patients	NNT ~14; modest but durable benefit; 2017 ACG recommends test-and-treat in uninvestigated dyspepsia age <60 without alarm features
PPI (4-8 weeks)	EPS subtype; H. pylori negative	Significant vs placebo (NNT ~8); less effective for PDS; reduces acid-sensitive visceral afferents
Acotiamide (fundus-relaxing prokinetic)	PDS subtype	Approved Japan; ↑ accommodation + ↑ antral motility; superior to placebo for PDS; not yet widely available outside Japan/Korea
TCA (low-dose amitriptyline 25 mg)	Pain-predominant FD (EPS)	HAPPINESS trial (Am J Gastroenterol 2015): ↓ adequate relief in PDS/EPS; first-line neuromodulator for FD refractory to acid suppression
Mirtazapine 15 mg QHS	Weight loss + early satiation in FD	↑ appetite; ↓ early satiation via H1 + 5-HT3 antagonism; useful for underweight FD patients with PDS features

Gastroparesis: Delayed gastric emptying (GES: >10% retention at 4 hours; or >60% at 2 hours) with symptoms of nausea, vomiting, postprandial fullness, bloating, early satiety in absence of obstruction. Causes: diabetic (most common — autonomic neuropathy), idiopathic (post-viral), post-surgical (vagotomy), drug-induced (opioids, GLP-1 agonists). Treatment: small, low-fat, low-fiber meals; metoclopramide (FDA approved; tardive dyskinesia risk >3 months — limit use); domperidone (available in Canada/Europe; QT prolongation); erythromycin IV (acute hospitalized) or oral (short-term); gastric electrical stimulation (Enterra) for refractory symptoms. Prucalopride (5-HT4 agonist) emerging evidence.

📚 Key References — Functional GI

Rome IV Criteria 2016 — Drossman DA (ed). Rome Foundation. Gastroenterology 2016;150:1257-1261.
AGA IBS Guidelines 2021 — Lacy BE et al. Gastroenterology 2021;161(2):520-545.
TARGET 1+2 (Rifaximin) — Pimentel M et al. NEJM 2011;364:22-32.
Linaclotide IBS-C — Chey WD et al. Am J Gastroenterol 2012;107:1702-1712.

5. Gastrointestinal Bleeding

GI bleeding is a common emergency with mortality 2-10% for upper GI bleeding (UGIB) and ~3% for lower GI bleeding (LGIB). This section integrates the 2021 ACG UGIB Guidelines, 2023 ACG LGIB Guidelines, Baveno VII Portal Hypertension Consensus (2022), and key risk stratification tools.

▼🔬 Algorithm: UGIB Management Pathway

▼5.1 Upper GI Bleeding — Resuscitation, Risk Stratification & Endoscopy

UGIB definition: Bleeding proximal to the ligament of Treitz. Presentation: hematemesis, coffee-ground emesis, melena (black tarry stool — blood transit >8 hours); hematochezia (bright red/maroon per rectum) in 10-15% of UGIB when rapid/massive.

Initial resuscitation: 2 large-bore IVs; crystalloid resuscitation; Restrictive transfusion strategy: transfuse pRBC when Hb <7 g/dL (TRIGGER trial; Villanueva NEJM 2013 — restrictive strategy improved outcomes vs liberal Hb <9 threshold in UGIB). Target Hb 7-9 g/dL. FFP/platelets for coagulopathy/thrombocytopenia. IV access + ICU monitoring for high-risk.

Risk Score	Parameters	Use	Low-Risk Threshold
Glasgow-Blatchford Score (GBS)	BUN, Hb, SBP, HR, melena, syncope, hepatic disease, cardiac failure	Pre-endoscopy; identifies patients safe for outpatient management	GBS = 0-1 → safe for early discharge without EGD (sensitivity 98-100% for intervention needed)
AIMS65	Albumin <3, INR >1.5, AMS (GCS <14), SBP ≤90, Age >65	Predicts in-hospital mortality; each factor = 1 point	Score 0 → <1% mortality; Score ≥3 → >10% mortality
Rockall Score (post-endoscopy)	Age, shock, comorbidities, diagnosis, endoscopic stigmata	Post-endoscopy re-bleeding risk and mortality	Score ≤2 → <5% re-bleeding risk; low-risk → early discharge

PPI before endoscopy: IV high-dose PPI (omeprazole 80 mg bolus → 8 mg/hr infusion) — reduces need for endoscopic hemostasis and reduces high-risk stigmata (does NOT reduce mortality). Start pre-endoscopy in all suspected peptic UGIB. After hemostasis for high-risk lesions (Forrest Ia/Ib/IIa/IIb): continue IV PPI 72 hrs → switch to oral PPI BID for 2 weeks.

Timing of endoscopy: Urgent EGD within 24 hours for all admitted UGIB (ACG 2021). EGD within 12 hours for hemodynamic instability/active bleeding/variceal suspected (with adequate resuscitation first). EGD <6 hours NOT routinely recommended (TIMING trial 2020, NEJM: no benefit vs 6-24 hr for stable patients).

Forrest Classification	Endoscopic Finding	Re-bleeding Risk	Management
Ia — Spurting arterial bleeding	Active pulsatile bleed	90%	Dual endoscopic therapy (injection + thermal/clip); hemoclips preferred; TAE if fails
Ib — Oozing bleeding	Active non-pulsatile ooze	50%	Endoscopic therapy (injection + clip/thermal)
IIa — Visible vessel (non-bleeding)	Protruding vessel	50%	Endoscopic therapy required (high-risk: always treat)
IIb — Adherent clot	Clot overlying ulcer	30%	Irrigation/removal of clot then treat underlying vessel
IIc — Flat pigmented spot	Hematin spot	7%	Medical therapy only (high-dose PPI); endoscopic therapy NOT needed
III — Clean base ulcer	No visible stigmata	3-5%	Medical therapy; early discharge safe; advance diet

🔑 Clinical Pearl — Prokinetics pre-EGD: IV erythromycin 250 mg (or metoclopramide 10 mg) 30-90 min before EGD significantly improves gastric visualization by clearing blood/clots (NNT ~3 to improve visualization). Reduces need for repeat EGD. Recommended by ACG 2021 guidelines before EGD in UGIB — often overlooked in practice.

▼5.2 Variceal Bleeding — Management Protocol

Variceal hemorrhage carries 20% in-hospital mortality and 60% 1-year re-bleeding risk without secondary prophylaxis. Classified as esophageal varices (EV) and gastric varices (GV — GOV1/GOV2, IGV1/IGV2).

⚡ Acute Variceal Bleeding — 5-Step Protocol (Baveno VII 2022)

Step 1 — Vasoactive drugs (start immediately, even before EGD): Terlipressin 2 mg IV q4-6h (preferred; ↓ mortality; not available in US) OR Somatostatin 250 mcg bolus → 250-500 mcg/hr OR Octreotide 50 mcg bolus → 50 mcg/hr. Continue 3-5 days.
Step 2 — Antibiotics (start at admission): Ceftriaxone 1 g IV daily × 7 days (preferred; reduces bacterial infections, SBP, and improves survival — Bernard NEJM 1999; norfloxacin less effective in high quinolone-resistance settings)
Step 3 — Endoscopy within 12 hours: EVL (endoscopic variceal ligation) for esophageal varices (preferred over sclerotherapy — fewer complications); cyanoacrylate injection for gastric varices
Step 4 — Early TIPS (preemptive TIPS within 72 hrs): For Child-Pugh B with active bleeding at EGD OR Child-Pugh C (10-13): significantly reduces 6-week failure/mortality (García-Pagán NEJM 2010: 3% vs 50% treatment failure). MELD ≤18-20 preferred; covered PTFE stents (e-TIPS)
Step 5 — Secondary prophylaxis (after 5 days of vasoactive therapy): NSBB (carvedilol 6.25-12.5 mg BID preferred OR propranolol 20-160 mg BID) + EVL sessions every 2-4 weeks until variceal obliteration

Balloon tamponade: Sengstaken-Blakemore (esophageal + gastric balloon) or Minnesota tube — temporary measure for refractory variceal bleeding as bridge to definitive therapy (TIPS); not used long-term; risk of esophageal necrosis if esophageal balloon inflated >24 hrs.

Primary prophylaxis of varices (Baveno VII): Screen for varices at time of cirrhosis diagnosis. Small varices without red signs + compensated: NSBB optional. Medium/large varices OR any red signs: NSBB (carvedilol preferred) OR EVL. Goal: HVPG reduction <12 mmHg or ≥20% reduction from baseline.

▼5.3 Lower GI Bleeding — Etiology, Risk Stratification & Management

LGIB definition: Bleeding distal to the ligament of Treitz; most frequently from colon/rectum. Most (80-85%) self-limited. Presentation: hematochezia or dark maroon stool.

Cause	Frequency	Clue	Diagnosis
Diverticular bleeding	30-40%	Painless, brisk, maroon — right-sided diverticula more common source despite higher prevalence left-sided	Colonoscopy; CT angiography if active; nuclear scan if slower
Anorectal (hemorrhoids, fissures)	20-25%	Bright red blood on paper/toilet; post-defecation; painless (hemorrhoids) or painful (fissure)	Anoscopy; colonoscopy to exclude proximal source
Colonic angiodysplasia (AVMs)	5-10%	Elderly; right-sided cecum; intermittent; associated with aortic stenosis (Heyde syndrome) and CKD	Colonoscopy (cherry-red flat lesion); CT angiography; capsule endoscopy for small bowel AVM
Ischemic colitis	5-10%	Acute abdominal pain followed by bloody diarrhea; watershed areas (splenic flexure, rectosigmoid); cardiovascular risk factors; post-aortic surgery	CT (thumbprinting, bowel wall thickening); colonoscopy (pale mucosa with submucosal hemorrhage); avoid colonoscopy if transmural ischemia suspected
IBD (UC/CD)	5-10%	Young patients; associated systemic symptoms; bloody diarrhea with urgency (UC)	Colonoscopy + biopsies; fecal calprotectin elevated
Colorectal neoplasia	5-10%	Change in bowel habit; weight loss; positive FIT; occult or overt bleeding	Colonoscopy + biopsy; CT colonography
Post-polypectomy bleeding	~5%	Delayed bleeding 7-14 days post-polypectomy	Colonoscopy; endoscopic clip/thermal hemostasis; often self-limited

Risk stratification (Oakland Score): Age, sex, prior LGIB, DRE blood, HR, SBP, Hb — score ≤8 → low risk (<1% adverse outcome) → outpatient management. Score >8 → inpatient colonoscopy.

Timing of colonoscopy: ACG 2023 — urgent colonoscopy within 24 hours for high-risk hemodynamically significant LGIB (after adequate bowel prep with 4-6L PEG). Standard colonoscopy within 24-48 hours for admitted stable LGIB. CT angiography preferred if colonoscopy impractical (prep not possible, ongoing brisk bleeding) — can detect active bleeding at rate ≥0.3-0.5 mL/min.

📚 Key References — GI Bleeding

ACG UGIB Guidelines 2021 — Laine L et al. Am J Gastroenterol 2021;116(5):899-917.
ACG LGIB Guidelines 2023 — Oakland K et al. Am J Gastroenterol 2023;118(2):208-231.
Villanueva RCT (Restrictive Transfusion) — NEJM 2013;368:11-21. Hb <7 threshold in UGIB.
TIMING Trial 2020 — Lau JYW et al. NEJM 2020;382:1299-1308. Urgent vs elective EGD in UGIB.
García-Pagán (Preemptive TIPS) — NEJM 2010;362:2370-2379. Early TIPS for high-risk variceal bleeding.
Baveno VII Consensus 2022 — de Franchis R et al. J Hepatol 2022;76:959-974.

▼📝 Practice Questions — GI Bleeding

Q1. A 72-year-old man on aspirin 81 mg and clopidogrel (drug-eluting stent placed 3 months ago) presents with hematemesis. BP 85/60 mmHg, HR 118. Hb 7.4 g/dL. After 2 units pRBC and 1L crystalloid, BP improves to 105/70 mmHg. What is the optimal management of his antiplatelet therapy and endoscopy timing?

Answer: Do NOT stop clopidogrel (stent is <12 months); EGD within 24 hours after adequate resuscitation

Drug-eluting stent placed <12 months ago → clopidogrel is mandatory — stopping risks in-stent thrombosis (30% mortality). Aspirin should be continued in most high-cardiovascular-risk patients with GI bleeding (ACG 2021). Consult cardiology. Regarding EGD timing: ACG 2021 recommends EGD within 24 hours for all admitted UGIB (not within 12 hrs unless active variceal suspected with hemodynamic instability — TIMING trial: no benefit to <6 hr EGD in hemodynamically stable patients). Pre-EGD: IV erythromycin 250 mg IV 30 min before EGD to clear stomach. Restrictive transfusion: Hb <7 g/dL trigger (achieved). IV high-dose PPI started empirically.

Q2. A 54-year-old man with Child-Pugh B cirrhosis is admitted with hematemesis. EGD shows Grade III esophageal varices with active spurting. He receives band ligation and vasoactive therapy (terlipressin). At 72 hours he has re-bled. What should be offered next?

Answer: Preemptive/salvage TIPS (covered stent)

This is refractory variceal bleeding — failed medical + endoscopic therapy. Salvage TIPS (transjugular intrahepatic portosystemic shunt) with covered PTFE stent is the treatment of choice. Additionally, based on Baveno VII, early preemptive TIPS within 72 hours should have been considered at admission since Child-Pugh B with active bleeding at index EGD qualifies (García-Pagán NEJM 2010: 3% vs 50% treatment failure with preemptive TIPS). MELD should be assessed — TIPS most beneficial if MELD ≤18-20. Balloon tamponade (Sengstaken-Blakemore) is a temporary bridge to TIPS if TIPS cannot be performed immediately (<24 hrs max esophageal balloon inflation).

6. Colorectal Cancer & Polyps

Colorectal cancer (CRC) is the 3rd most common cancer and 2nd leading cause of cancer death worldwide. 95% are adenocarcinomas. The adenoma-carcinoma sequence provides a 10–15 year window for detection and prevention. This section integrates the 2021 USMSTF Multi-Society Screening Guidelines, 2020 ACG Colorectal Cancer Prevention Guidelines, and landmark screening trial data.

▼6.1 Colorectal Polyps — Classification & Risk

Polyp Type	Malignant Potential	Histological Features	Surveillance Interval
Hyperplastic polyp (HP)	Negligible	Serrated but non-dysplastic; predominantly rectosigmoid; saw-tooth pattern without cytologic atypia	Routine screening (10 yr) if ≤20 HPs <10 mm in rectosigmoid
Tubular adenoma (TA)	Low (villous component <25%)	Dysplastic tubular glands; low-grade dysplasia typical	1-2 adenomas <10 mm, LGD: 7-10 yr; 3-4 adenomas: 3-5 yr
Tubulovillous adenoma	Intermediate (25-75% villous)	Mixed tubular/villous architecture; higher dysplasia rate	1 tubulovillous <10 mm LGD: 3-5 yr; same as advanced adenoma if HGD or ≥10 mm
Villous adenoma	High (>75% villous; 40% harbour cancer)	Predominantly villous fronds; higher rate HGD; large rectal villous adenomas secrete mucus → hypokalemia	3 yr after complete resection if HGD; verify complete resection
Sessile Serrated Lesion (SSL)	Moderate-high (BRAF mutation → MLH1 silencing → MSI-H pathway)	Dilated serrated crypts with horizontal/inverted T-shape crypts; typically right-sided, flat, covered with mucus cap	1-2 SSLs <10 mm without dysplasia: 5 yr; SSL ≥10 mm or dysplasia: 3 yr
Traditional Serrated Adenoma (TSA)	High (KRAS/BRAF mutation)	Ectopic crypts, villous architecture, pinecone appearance; left-sided, pedunculated	3 yr (same as advanced adenoma)
Advanced adenoma (AA)	High	≥10 mm OR HGD OR ≥25% villous component	3 yr after complete polypectomy

🔑 High-Yield — Polyposis Syndromes:
• FAP (APC gene) — hundreds to thousands of adenomas; 100% lifetime CRC risk; prophylactic colectomy by age 20-25; also causes desmoid tumors, CHRPE, Gardner syndrome features (osteomas, epidermoid cysts, supernumerary teeth)
• MUTYH-associated polyposis (MAP) — AR inheritance; 10-100 adenomas; MUTYH biallelic mutations; consider in FAP phenotype without APC mutation
• Lynch Syndrome (HNPCC) — MMR gene mutations (MLH1, MSH2, MSH6, PMS2, EPCAM); MSI-H/dMMR tumors; Amsterdam II criteria; lifetime CRC risk 40-80%; also endometrial, ovarian, gastric, urinary tract cancers; surveillance colonoscopy every 1-2 years from age 20-25
• Peutz-Jeghers — STK11/LKB1; hamartomatous polyps + mucocutaneous melanotic macules; ↑ GI + extraintestinal cancer risk

▼6.2 CRC Screening — Modalities & Guidelines

USMSTF 2021 / ACG 2021: Begin average-risk screening at age 45 years (updated from 50 — reflects rising CRC incidence in adults 40-49, ACS 2018; ACG 2021 aligns). Continue until age 75 (individualize 76-85; stop >85).

Screening Modality	Interval	Sensitivity for CRC	Notes
Colonoscopy	10 yr (normal; average risk)	95%	Gold standard; allows biopsy + polypectomy; requires bowel prep; perforation ~1/1000; preferred "Tier 1" test
FIT (Fecal Immunochemical Test)	Annual	79% (single test); ↑ with annual testing	Non-invasive; quantitative; patient-preferred; positive → diagnostic colonoscopy; "Tier 1" stool test (ACG 2021)
Stool DNA (Cologuard®)	1-3 yr	92% (single test); higher false-positive rate than FIT	Multi-target DNA + FIT combined; 10% FP rate; positive → diagnostic colonoscopy; approved by FDA 2014
CT Colonography (CTC)	5 yr	96% for polyps ≥10 mm; 73-84% for 6-9 mm	Non-invasive; requires bowel prep; radiation; "Tier 2"; positive → optical colonoscopy
Flexible Sigmoidoscopy	5 yr alone; 10 yr + annual FIT	~75% (misses right-sided lesions)	"Tier 2"; does not visualize proximal colon; combination with annual FIT improves detection
Serum Septin9 (blood-based)	Annual	68%	Lowest sensitivity; acceptable if patient declines all other tests; positive → colonoscopy

▼6.3 CRC Staging & Treatment Overview

TNM/AJCC 8th Edition Staging:

Stage	TNM	5-Year Survival	Treatment
Stage I	T1-2, N0, M0	90-95%	Surgical resection alone; no adjuvant chemotherapy
Stage II (A/B/C)	T3-4, N0, M0	75-85%	Surgery; adjuvant FOLFOX considered for high-risk features (T4, perforation, LVI, PNI, <12 LN examined, MSS); MSI-H stage II → no benefit from 5-FU-based adjuvant chemo
Stage III (A/B/C)	Any T, N1-2, M0	40-80%	Surgery + adjuvant FOLFOX × 6 months (or CAPOX × 3-6 months); MSI-H stage III → adjuvant chemo still recommended
Stage IV (metastatic)	Any T, any N, M1	10-15% (5-yr)	FOLFOX or FOLFIRI ± bevacizumab (anti-VEGF) or cetuximab/panitumumab (anti-EGFR — RAS/RAF wildtype only); MSI-H/dMMR → pembrolizumab first-line (KEYNOTE-177); resection of isolated liver/lung metastases in selected patients

Rectal cancer specifics: Preoperative staging with MRI pelvis (T and N staging, CRM involvement). Locally advanced (T3/T4 or N+): neoadjuvant chemoradiotherapy → total mesorectal excision (TME). Complete clinical response after neoadjuvant → "watch and wait" (non-operative management) emerging strategy at experienced centers.

🔑 Molecular Biomarkers in CRC — Board-Exam Essentials:
• MSI-H/dMMR (~15% all CRC; ~4% metastatic CRC) — Lynch syndrome (30%) or sporadic (MLH1 promoter methylation, 70%); best response to immune checkpoint inhibitors (pembrolizumab, nivolumab); poor response to 5-FU alone
• RAS mutation (KRAS/NRAS) — ~50% CRC; predicts resistance to anti-EGFR antibodies (cetuximab, panitumumab); test before anti-EGFR therapy
• BRAF V600E mutation — ~10% CRC; poor prognosis; resistance to anti-EGFR; combination BRAF + MEK inhibitor + EGFR inhibitor (BEACON CRC: encorafenib + cetuximab ± binimetinib); test routinely
• HER2 amplification — ~3% CRC; trastuzumab + pertuzumab (MyPathway) or trastuzumab + lapatinib (HERACLES) in HER2+ RAS/BRAF wildtype CRC

📚 Key References — CRC & Polyps

USMSTF Multi-Society CRC Screening 2021 — Quintero E / Knudsen AB et al. Gastroenterology 2021;160(8):2819-2846.
ACG CRC Prevention Guidelines 2021 — Shaukat A et al. Am J Gastroenterol 2021;116(3):458-479.
KEYNOTE-177 — André T et al. NEJM 2020;383:2207-2218. Pembrolizumab vs chemo first-line for MSI-H/dMMR mCRC.
BEACON CRC — Kopetz S et al. NEJM 2019;381:1632-1643. Encorafenib + cetuximab for BRAF V600E mCRC.

7. Viral Hepatitis B & C

Viral hepatitis remains a major global health burden. HBV affects ~296 million people globally (2 billion ever-infected); HCV ~58 million with chronic infection. Both are leading causes of cirrhosis and hepatocellular carcinoma. This section covers current AASLD 2018/2023 HBV Guidelines, AASLD/IDSA HCV Guidance 2024, and WHO elimination goals.

▼7.1 HBV — Serological Markers & Natural History

Marker	Interpretation
HBsAg (+)	Active HBV infection (acute or chronic). Persists >6 months = chronic HBV
HBsAb (+), HBcAb (-)	Vaccination response (immunity from vaccine)
HBsAb (+), HBcAb (+)	Past natural infection → recovered with immunity
HBcAb IgM (+)	Acute HBV infection (window period: HBsAg may be absent)
HBcAb IgG (+), HBsAg (-), HBsAb (-)	"Isolated core antibody" — past infection with waning immunity OR occult HBV; check HBV DNA
HBeAg (+)	Active viral replication; high infectivity. In HBeAg+ chronic HBV: high HBV DNA (>20,000 IU/mL)
HBeAb (+), HBeAg (-)	HBeAg seroconversion — often marks immune control; HBV DNA ↓; but replication persists (pre-core/core promoter mutants)
HBsAg quantitative (qHBsAg)	<1,000 IU/mL predicts functional cure in select patients; used in monitoring and predicting treatment response to PEG-IFN

Phase	HBeAg	HBV DNA	ALT	Liver Biopsy	Treatment
Phase 1 — Immune Tolerant	+	Very high (>10⁶-10⁷)	Normal	Minimal inflammation	Generally NOT treated (poor IFN/NUC response; high DNA but no liver injury); Exception: age >30 or family history HCC → consider biopsy
Phase 2 — Immune Active (HBeAg+)	+	High (>20,000)	Elevated (>2×ULN)	Moderate-severe inflammation/fibrosis	TREAT: NUC (TDF/TAF/ETV) or PEG-IFN-α2a
Phase 3 — Immune Control (inactive carrier)	−	Low (<2,000) or undetectable	Normal (persistently)	Minimal	No treatment; HCC surveillance if cirrhosis or risk factors; monitor every 6-12 months
Phase 4 — Immune Escape (HBeAg− CHB)	−	Variable (2,000-20,000+)	Fluctuating elevated	Active inflammation; progressive fibrosis	TREAT if HBV DNA >2,000 + elevated ALT or significant fibrosis
Phase 5 — HBsAg loss ("functional cure")	−	Undetectable	Normal	Resolution of inflammation	Discontinue NUC if safe; HCC surveillance continues if previously cirrhotic

▼7.2 HBV Treatment — Antivirals, HCC Surveillance & Special Populations

⚡ HBV Treatment Indications (AASLD 2018/2023)

Treat if: HBV DNA >20,000 IU/mL + ALT >2×ULN (HBeAg+) OR HBV DNA >2,000 IU/mL + ALT >2×ULN (HBeAg−) OR any level DNA + cirrhosis OR significant fibrosis (F≥2 on biopsy)
Prevent reactivation: Anti-HBc+ patients receiving rituximab, anti-CD20, chemotherapy, high-dose steroids, TNF inhibitors → prophylactic NUC
First-line NUCs: Tenofovir alafenamide (TAF) 25 mg QD (preferred — less bone/renal toxicity than TDF; approved 2016) OR Tenofovir disoproxil fumarate (TDF) 300 mg QD OR Entecavir (ETV) 0.5 mg QD (1 mg if lamivudine-resistant). ALL have high barrier to resistance. Avoid lamivudine/adefovir (low barrier to resistance).
PEG-IFN-α2a (180 mcg SC weekly × 48 weeks) — finite therapy; may achieve sustained off-treatment response + HBsAg decline; use in HBeAg+ with high ALT, low DNA (<10⁷), genotype A/B, no cirrhosis; contraindicated in decompensated cirrhosis
Goal of therapy: Suppress HBV DNA to undetectable; normalize ALT; HBeAg seroconversion; long-term: prevent progression to cirrhosis/HCC; HBsAg loss (functional cure) in <5% on NUC

HCC Surveillance in CHB: Ultrasound every 6 months ± AFP (AASLD; EASL recommends US alone). High-risk requiring surveillance: All cirrhotic HBV patients; non-cirrhotic HBV if: Asian male >40, Asian female >50, African descent >20, family history HCC, HBV DNA >10,000 IU/mL.

Pregnancy: Screen all pregnant women for HBsAg. Infected: check HBV DNA. If DNA >200,000 IU/mL → TDF from 28 weeks to prevent perinatal transmission (plus HBIG + vaccine to infant within 12 hrs of birth). TAF not yet FDA-approved in pregnancy (limited data). Lamivudine alternative.

▼7.3 Hepatitis C — Diagnosis, DAA Therapy & Cure

HCV is curable in >95% of patients with direct-acting antivirals (DAAs). WHO target: eliminate HCV as public health threat by 2030. Screening: Universal one-time screening for all adults ≥18 years (USPSTF 2020, Grade B); universal screening in pregnancy; annual if ongoing IDU risk.

Diagnosis: Anti-HCV antibody (ELISA) → if positive, confirm with HCV RNA (PCR). Anti-HCV+ but RNA negative = resolved infection (spontaneous clearance or treated). HCV genotyping (1a, 1b, 2, 3, 4, 5, 6) still useful for some regimens but pangenotypic DAAs make genotype less critical.

DAA Regimen	Genotype	Duration	SVR12 Rate	Key Notes
Glecaprevir/Pibrentasvir (Mavyret®) — NS3/4A + NS5A inhibitor	Pangenotypic (1-6)	8 weeks (treatment-naïve, no cirrhosis); 12 weeks (compensated cirrhosis); 16 weeks (decompensated/prior tx failure)	97-99%	No renal dose adjustment needed; approved CKD including dialysis; Avoid in decompensated cirrhosis (Child B/C)
Sofosbuvir/Velpatasvir (Epclusa®) — NS5B + NS5A inhibitor	Pangenotypic (1-6)	12 weeks (all; with or without compensated cirrhosis); 12 weeks + ribavirin for decompensated cirrhosis	97-99% (compensated); 83-94% (decompensated)	Acceptable in decompensated cirrhosis (with ribavirin); avoid if liver transplant candidate on cyclosporine; NS5A RASs may affect GT3
Sofosbuvir/Velpatasvir/Voxilaprevir (Vosevi®) — NS5B + NS5A + NS3/4A	Pangenotypic (1-6)	12 weeks	>96% including prior DAA failures	For NS5A inhibitor failures; prior sofosbuvir failures; GT3 with decompensated cirrhosis (with ribavirin)
Ledipasvir/Sofosbuvir (Harvoni®) — NS5A + NS5B	GT 1, 4, 5, 6	8 weeks (GT1, treatment-naïve, no cirrhosis, HCV RNA <6 million); 12 weeks (standard)	94-99%	Not for GT2/3; older regimen but still widely used; renal caution (avoid if eGFR <30)

SVR12 (Sustained Virological Response at 12 weeks) = cure — HCV RNA undetectable 12 weeks after end of treatment. SVR12 achieved = <1% late relapse. Post-SVR: regression of fibrosis; ↓ cirrhosis complications; ↓ HCC risk (80% reduction but NOT zero in cirrhosis — continue HCC surveillance). Monitor liver function annually; discontinue HCC surveillance only if non-cirrhotic pre-treatment.

🔑 Drug Interactions — HCV DAAs: NS3/4A inhibitors (glecaprevir, grazoprevir, voxilaprevir) are CYP3A4 substrates and strong P-gp inhibitors — major interactions: statins (↑ statin levels → myopathy), tacrolimus/cyclosporine (↑ calcineurin inhibitor levels), rifampin (inducer → ↓ DAA levels → avoid). Always check drug interactions before prescribing DAAs (hep-druginteractions.org).

📚 Key References — Viral Hepatitis

AASLD HBV Guidance 2018 (updated 2023) — Terrault NA et al. Hepatology 2018;67(4):1560-1599.
AASLD/IDSA HCV Guidance 2024 — www.hcvguidelines.org (continuously updated)
EXPEDITION-4 (G/P in renal impairment) — Gane E et al. NEJM 2017;377:1448-1455.
ASTRAL-1 (SOF/VEL) — Feld JJ et al. NEJM 2015;373:2599-2607.

▼📝 Practice Questions — Viral Hepatitis

Q1. A 34-year-old Thai woman presents at 28 weeks of pregnancy. Routine labs: HBsAg (+), HBeAg (+), HBV DNA 850,000 IU/mL. AST/ALT normal. She has no prior HBV treatment. What is the correct management?

Answer: Start TDF (tenofovir disoproxil fumarate) 300 mg QD from 28 weeks + give infant HBIG + HBV vaccine within 12 hours of birth

HBV DNA >200,000 IU/mL in pregnancy → high risk of vertical transmission (up to 90% in HBeAg+ mothers) despite passive-active immunoprophylaxis of infant. TDF from 28 weeks gestation reduces perinatal transmission to <1% (AASLD 2023; WHO guidelines). TDF (not TAF — insufficient pregnancy safety data) is the agent of choice. Continue TDF for ≥4–12 weeks postpartum. Breastfeeding is safe on TDF (minimal drug excretion in breast milk). The infant must receive both HBIG (0.5 mL IM) AND HBV vaccine series starting within 12 hours of birth — regardless of maternal TDF therapy. Note: this mother is in the immune tolerant phase (normal ALT, high DNA) — she does NOT require treatment for her own HBV at this stage, only for prevention of vertical transmission.

Q2. A 48-year-old HIV-positive man on efavirenz/emtricitabine/tenofovir (Atripla®) is found to have HCV genotype 1b, HCV RNA 2.4 million IU/mL, FIB-4 1.8. He has no cirrhosis. Which HCV DAA regimen is most appropriate?

Answer: Sofosbuvir/velpatasvir (Epclusa) 12 weeks OR glecaprevir/pibrentasvir (Mavyret) 8 weeks — check drug interactions first

HIV/HCV coinfection is treated with the same pangenotypic DAA regimens as HCV monoinfection — SVR rates equivalent (~97%). Critical step: check drug-drug interactions between DAAs and ART at hep-druginteractions.org. Efavirenz is a CYP3A4 inducer → significantly reduces glecaprevir and pibrentasvir levels — Mavyret is NOT recommended with efavirenz. Sofosbuvir/velpatasvir (Epclusa) has no significant interaction with efavirenz — preferred regimen here. Alternative: switch ART to dolutegravir-based regimen, then use Mavyret. No cirrhosis + treatment-naïve + genotype 1b → SOF/VEL 12 weeks → expected SVR >97%. Confirm HBsAg/HBcAb before starting DAAs — HBV reactivation risk with HCV DAAs if HBsAg+.

Q3. A 58-year-old man with chronic HBV on entecavir (HBV DNA undetectable × 3 years) is started on rituximab for diffuse large B-cell lymphoma. What precaution is required?

Answer: Continue entecavir throughout rituximab therapy and for 12–18 months after completion — do NOT stop

Rituximab (anti-CD20) causes profound B-cell depletion → high risk of HBV reactivation (up to 40% without prophylaxis; fatality rate up to 30% from reactivation hepatitis). All HBsAg+ patients receiving rituximab/anti-CD20/chemotherapy must be on prophylactic antiviral therapy. Entecavir (or TDF/TAF) should be continued for 12–18 months after last dose of rituximab (prolonged due to B-cell recovery timeline). Also screen all rituximab candidates for HBsAg AND HBcAb (core antibody) — HBcAb+ HBsAg− (past infection) patients also need prophylactic lamivudine/entecavir with rituximab due to occult HBV reactivation risk.

8. MASLD / MASH — Metabolic Dysfunction-Associated Steatotic Liver Disease

In 2023, the global nomenclature changed from NAFLD/NASH to MASLD (Metabolic dysfunction-Associated Steatotic Liver Disease) and MASH (Metabolic dysfunction-Associated Steatohepatitis) by multi-society Delphi consensus (AGA, EASL, AASLD, AISF, SLEF, ALEH). MASLD is now the most common liver disease worldwide — affecting ~32% of adults globally. Leading cause of cirrhosis, liver transplantation, and HCC in Western countries.

▼8.1 MASLD — Definition, Diagnosis & Non-Invasive Tests

MASLD Definition (2023 consensus): Hepatic steatosis (imaging or histology) + ≥1 of 5 cardiometabolic risk criteria: (1) BMI ≥25 (or ≥23 in Asian populations), (2) fasting glucose ≥100 mg/dL or T2DM, (3) BP ≥130/85 or antihypertensive therapy, (4) TG ≥150 mg/dL or lipid-lowering therapy, (5) HDL <40 (men) or <50 (women) mg/dL. MetALD: MASLD + alcohol 140-350 g/week (men) or 70-140 g/week (women).

Non-Invasive Test (NIT)	What It Measures	Cutoffs	Clinical Use
FIB-4 Index	Fibrosis staging: Age × AST / (Platelet × √ALT)	<1.3 = low risk (F0-1); 1.3-2.67 = indeterminate; >2.67 = high risk (F3-4)	First-line screening; AGA 2023 recommends FIB-4 as initial NIT in all MASLD patients; age-adjusted cutoffs (≥65 yr: use 2.0 lower cutoff)
Liver Stiffness (LSM) — Vibration Controlled Transient Elastography (VCTE/FibroScan®)	Liver stiffness in kPa → correlates with fibrosis stage	<8 kPa = low risk; 8-12 kPa = indeterminate; >12 kPa = high risk (F3-4)	Second-line after FIB-4 indeterminate; also diagnoses portal hypertension (>21 kPa = cHPTN in MASLD per Baveno VII)
PDFF (Proton Density Fat Fraction) — MRI-PDFF	Hepatic steatosis grade (% fat fraction)	<5% = no steatosis; 5-17% mild; 17-22% moderate; >22% severe	Gold standard non-invasive steatosis quantification; used in clinical trials as endpoint; not routine clinical use
ELF Score (Enhanced Liver Fibrosis)	Serum biomarkers: HA, PIIINP, TIMP-1	<7.7 = low; 7.7-9.8 = moderate; >9.8 = high fibrosis risk	FDA-approved; approved in Europe; useful when FIB-4 indeterminate; blood-based
Liver Biopsy	MASH histology (steatosis, lobular inflammation, ballooning) + NAS score + fibrosis staging (F0-4 Kleiner)	NAS ≥5 with lobular inflammation and ballooning = MASH	Gold standard; required when: diagnosis uncertain, exclude other etiologies, before enrolling in trials, or if considering pharmacotherapy

AGA 2023 MASLD Clinical Care Pathway: (1) FIB-4 for all MASLD → (2) if <1.3: reassure, treat metabolic risk, retest every 1-2 years → (3) if >2.67 or 1.3-2.67 + high clinical risk: refer hepatology + LSM (FibroScan) → (4) if LSM <8 kPa: low risk but monitor; if >12 kPa: specialist management, biopsy consideration, HCC surveillance.

▼8.2 MASH Treatment — Lifestyle, Approved Pharmacotherapy & Emerging Therapies

Lifestyle modification — cornerstone of treatment: Weight loss 5-10% → improves steatosis and inflammation; >10% → may improve fibrosis; >7% → improves NAS score; Mediterranean diet; moderate-intensity exercise ≥150 min/week. Bariatric surgery (particularly Roux-en-Y gastric bypass) most effective for MASH — improves histology including fibrosis in 65-85%.

Drug	Mechanism	Status / Approval	Key Trial	Notes
Resmetirom (Rezdiffra®)	Thyroid hormone receptor-β (THRβ) agonist — selective hepatic; ↓ lipogenesis, ↑ β-oxidation, ↓ triglycerides	FDA APPROVED March 2024 — first drug approved for MASH with liver fibrosis (F2-F3)	MAESTRO-NASH (NEJM 2024): MASH resolution without worsening fibrosis: 25.9% vs 14.2% (80 mg); fibrosis improvement ≥1 stage: 24.2% vs 14.4%	Dose: 80 mg or 100 mg QD (weight-based); thyroid precautions; modest QT effect; check thyroid function; approved for F2-F3 non-cirrhotic MASH; LDLR upregulation — monitor lipids
Semaglutide (GLP-1 RA)	GLP-1 agonist → ↑ satiety, ↓ hepatic lipogenesis, ↓ inflammation	Off-label for MASH; MASH resolution without fibrosis improvement in phase 2; Phase 3 (ESSENCE) completed — MASH resolution 62.9% vs 34.3% at 72 weeks; fibrosis improvement 37% vs 22%	ESSENCE Phase 3 (NEJM 2025): Met both co-primary endpoints; FDA submission pending (2025)	Preferred in MASLD + T2DM + obesity; also proven cardiovascular benefit (SURPASS); weekly SC injection; GI side effects (nausea)
Pioglitazone	PPARγ agonist → ↑ adiponectin, ↑ insulin sensitivity, ↓ hepatic fat	Off-label; strong evidence for MASH; recommended by AASLD for MASH + T2DM/prediabetes	Multiple RCTs; Belfort NEJM 2006; Cusi 2016 NEJM: 58% MASH resolution vs 17% placebo	Weight gain (2-3 kg); fluid retention; bladder cancer concern (long-term use >2 yr); bone fracture risk in women; contraindicated in heart failure
Vitamin E 800 IU/day	Antioxidant → ↓ oxidative stress-mediated hepatocyte injury	Off-label; AASLD recommended for non-diabetic MASH patients with significant fibrosis	PIVENS trial (NEJM 2010): 43% MASH resolution vs 19% placebo; no cirrhosis benefit	Not recommended in T2DM (no benefit in PIVENS diabetic subgroup); concern re hemorrhagic stroke and all-cause mortality at high doses (meta-analysis); use with caution >400 IU/day

🔑 MASLD + HCC: HCC can occur in non-cirrhotic MASLD (up to 25% of MASLD-HCC arise without cirrhosis — unlike viral hepatitis-HCC which is nearly always cirrhotic). This means standard ultrasound surveillance algorithms based on cirrhosis alone will miss a proportion of MASLD-HCC. Currently, HCC surveillance recommended for MASLD cirrhosis (US q6mo ± AFP). Non-cirrhotic MASLD with advanced fibrosis (F3) → surveillance being studied in clinical trials.

📚 Key References — MASLD/MASH

Multi-Society Nomenclature Consensus 2023 — Rinella ME et al. Hepatology 2023;78(6):1966-1986. MASLD/MASH terminology.
MAESTRO-NASH 2024 — Harrison SA et al. NEJM 2024;390:497-509. Resmetirom FDA approval.
AGA MASLD Care Pathway 2023 — Loomba R et al. Gastroenterology 2023;165(5):1297-1305. FIB-4 based pathway.
PIVENS Trial — Sanyal AJ et al. NEJM 2010;362:1675-1685. Vitamin E vs pioglitazone vs placebo.

9. Liver Cirrhosis & Portal Hypertension Complications

Cirrhosis is the end-stage of chronic liver injury, characterized by fibrous tissue replacement of hepatic parenchyma and formation of regenerative nodules. HVPG ≥10 mmHg = clinically significant portal hypertension (cHPTN) — threshold for decompensation (ascites, varices, SBP, HRS, HE). Baveno VII (2022) and AASLD Practice Guidelines (2021) provide the current evidence base.

Child-Pugh Parameter	1 Point	2 Points	3 Points
Bilirubin (mg/dL)	<2	2-3	>3
Albumin (g/dL)	>3.5	2.8-3.5	<2.8
INR (prothrombin time)	<1.7	1.7-2.3	>2.3
Ascites	None	Mild-moderate (diuretic-responsive)	Severe (diuretic-refractory)
Hepatic Encephalopathy	None	Grade 1-2	Grade 3-4

SAAG	Etiology	Examples
≥1.1 g/dL (HIGH gradient)	Portal hypertension	Cirrhosis (most common), right heart failure (cardiac ascites — high protein >2.5 g/dL), Budd-Chiari, portal vein thrombosis, hepatic sinusoidal obstruction syndrome
<1.1 g/dL (LOW gradient)	Non-portal hypertension	Peritoneal carcinomatosis, TB peritonitis, nephrotic syndrome, pancreatitis, vasculitis, mesothelioma

Scenario	Treatment	Duration
Community-acquired SBP (no prior quinolone use, no hospital exposure)	Cefotaxime 2 g IV q8h (or ceftriaxone 1 g IV daily) — first-line	5 days; IV albumin 1.5 g/kg day 1 + 1 g/kg day 3 (Sort NEJM 1999: ↓ renal failure 33%→10%, ↓ mortality 29%→10%)
Hospital-acquired SBP or prior quinolone prophylaxis	Broader coverage: piperacillin-tazobactam or meropenem (if MDR suspected or 3rd-gen cephalosporin-resistant area)	5-7 days; albumin as above
Secondary prophylaxis (after SBP episode)	Norfloxacin 400 mg QD PO (or TMP-SMX 1 DS daily) — lifelong until liver transplant or ascites resolution	Indefinite; reduces 1-year recurrence from 70% to 20%
Primary prophylaxis (high-risk: ascites protein <1.5 g/dL + renal/liver dysfunction)	Norfloxacin 400 mg QD OR ciprofloxacin 500 mg QD	Until resolved/transplant; Fernández HEPATOLOGY 2007: ↓ SBP + HRS + 3-mo mortality

West Haven Grade	Clinical Features
Covert HE (CHE) — Grade 0/MHE	Abnormal psychometric testing only; impaired driving; impaired work performance; no clinical signs
Grade 1	Mild confusion, euphoria/depression, shortened attention, sleep disturbance; subtle personality change
Grade 2	Lethargy, disorientation (time/place), asterixis (flapping tremor); slurred speech; inappropriate behavior
Grade 3	Stupor, response to stimuli only; gross disorientation; rigidity; hyperreflexia; positive Babinski
Grade 4	Coma (unresponsive); may retain response to pain

Type	Onset	Clinical Feature	Treatment	Prognosis
HRS-AKI (formerly Type 1)	Rapid (<2 weeks)	Precipitant often present: SBP, large LVP without albumin, sepsis, dehydration; Cr >2.5 mg/dL common; oliguria	Terlipressin 1-2 mg IV q4-6h OR 2 mg/day continuous + albumin 20-40 g/day (FDA approved 2022 — CONFIRM trial); if no terlipressin: norepinephrine (ICU) + albumin; Midodrine + octreotide + albumin (outpatient, weaker evidence)	Poor without transplant; ~50% respond to terlipressin; bridge to liver transplant
HRS-CKD (formerly Type 2)	Gradual	Refractory ascites; Cr 1.5-2.5 mg/dL; relatively stable; no rapid deterioration	TIPS if eligible; same vasoconstrictors; liver transplant evaluation	Moderate; transplant is definitive treatment