Master Gastrointestinal System
for PLAB 1

What the PLAB 1 Tests in Gastrointestinal System

PLAB 1 Gastrointestinal System tests the ability to manage common acute and chronic presentations: dysphagia, dyspepsia, altered bowel habit, rectal bleeding, jaundice, and abdominal pain. Candidates must differentiate causes (e.g., reflux vs. Barrett's, IBS vs. IBD), know first-line investigations (e.g., oesophagogastroduodenoscopy for dysphagia, faecal calprotectin for IBD), and apply management guidelines (e.g., NICE for dyspepsia, BSG for colorectal cancer screening). Key decisions include when to refer urgently (e.g., red-flag symptoms for upper GI cancer), prescribe Helicobacter pylori eradication (triple therapy: amoxicillin, clarithromycin, PPI), and manage complications (e.g., variceal bleeding with terlipressin and antibiotics). Knowledge of surgical emergencies (e.g., acute cholecystitis, appendicitis, perforated ulcer) and their scoring systems (e.g., Alvarado score) is essential.

High-Yield Concepts

• Dyspepsia and H. pylori Management (NICE CG184): For uninvestigated dyspepsia without alarm symptoms, offer a test-and-treat strategy using a 13C-urea breath test or stool antigen test. First-line eradication is triple therapy: PPI (e.g., omeprazole 20 mg bd), amoxicillin 1 g bd, and clarithromycin 500 mg bd for 7 days. If penicillin-allergic, use metronidazole 400 mg bd instead of amoxicillin. Confirm eradication with a breath test at least 4 weeks after treatment.
• Upper GI Bleeding Management (BSG Guidelines): In acute variceal bleeding, start terlipressin 2 mg IV q6h and prophylactic antibiotics (e.g., ceftriaxone 1 g IV daily). For non-variceal bleeding, use a Rockall score (≥5 predicts high mortality). Perform urgent endoscopy within 24 hours for unstable patients. Post-endoscopy, high-dose PPI (e.g., omeprazole 80 mg IV bolus then 8 mg/h infusion) for 72 hours if high-risk stigmata (active bleeding, visible vessel).
• Colorectal Cancer Screening and Referral (NICE NG12): Refer urgently (2-week wait) for: aged ≥40 with unexplained weight loss and abdominal pain, aged ≥50 with unexplained rectal bleeding, aged ≥60 with iron-deficiency anaemia (Hb <110 g/L in men, <100 g/L in women). Faecal immunochemical test (FIT) is used in primary care for low-risk symptoms (cut-off ≥10 µg Hb/g faeces).
• Irritable Bowel Syndrome (IBS) Diagnosis (Rome IV Criteria): Recurrent abdominal pain at least 1 day/week in the last 3 months, associated with ≥2 of: defecation, change in stool frequency, or change in stool form. First-line management: lifestyle advice, soluble fibre (e.g., ispaghula husk), and antispasmodics (e.g., mebeverine). For diarrhoea-predominant IBS, consider loperamide; for constipation-predominant, linaclotide if laxatives fail.
• Inflammatory Bowel Disease (IBD) Differentiation: Ulcerative colitis (UC): continuous inflammation from rectum, bloody diarrhoea, crypt abscesses on biopsy. Crohn's disease: skip lesions, transmural inflammation, cobblestone mucosa, fistulas, perianal disease. Faecal calprotectin >50 µg/g suggests IBD. First-line for mild-to-moderate UC: mesalazine (oral + rectal). For Crohn's: budesonide for ileocaecal disease, or prednisolone for more extensive.
• Acute Cholecystitis (Tokyo Guidelines 2018): Diagnosis requires local signs (Murphy's sign, RUQ mass/pain), systemic signs (fever, raised CRP), and imaging (ultrasound showing gallbladder wall >4 mm, pericholecystic fluid). Severity grading: Grade I (mild) – no organ dysfunction; Grade II (moderate) – elevated WBC, palpable mass, duration >72 hours; Grade III (severe) – organ failure. First-line: IV antibiotics (e.g., co-amoxiclav 1.2 g tds) and early laparoscopic cholecystectomy within 7 days.
• Appendicitis Scoring (Alvarado Score): Score based on: migration of pain (1), anorexia/ketones in urine (1), nausea/vomiting (1), tenderness in RLQ (2), rebound pain (1), pyrexia >37.3°C (1), leukocytosis >10,000/µL (2), left shift >75% neutrophils (1). Total: ≤4 – low risk (observe); 5-6 – intermediate (CT or ultrasound); ≥7 – high risk (proceed to surgery).
• Jaundice Workup and Cholestasis: Differentiate pre-hepatic (unconjugated bilirubin, normal LFTs), hepatocellular (raised ALT/AST, conjugated bilirubin), and obstructive (raised ALP, GGT, conjugated bilirubin, dilated bile ducts on ultrasound). For obstructive jaundice, urgent ERCP within 24-48 hours if cholangitis (Charcot's triad: fever, RUQ pain, jaundice). First-line imaging: ultrasound abdomen.

Common Traps in Gastrointestinal System Questions

• Confusing IBS with IBD: IBS has no inflammation, normal calprotectin, and no blood in stool; IBD has raised calprotectin and rectal bleeding.
• Assuming all dyspepsia requires endoscopy: NICE advises test-and-treat for H. pylori in patients under 55 without alarm symptoms.
• Forgetting that melaena indicates upper GI bleeding (above the ligament of Treitz), not lower GI; always consider varices or peptic ulcer.
• Using a PPI alone for H. pylori without antibiotics: monotherapy fails and promotes resistance; always use triple therapy.
• Treating acute cholecystitis with antibiotics alone without planning cholecystectomy: definitive management is surgical within 7 days for Grade I/II.
• Missing that a positive faecal immunochemical test (FIT) requires urgent colonoscopy even if symptoms are mild; it is not a screening test alone.

How to Revise Gastrointestinal System for the PLAB 1

For PLAB 1 Gastrointestinal, prioritise NICE guidelines for dyspepsia, colorectal cancer referral, and upper GI bleeding. Questions often present a clinical scenario (e.g., a 60-year-old with dysphagia and weight loss) and ask for the next step (urgent endoscopy) or first-line drug (PPI for reflux). Practise applying scoring systems (Alvarado, Rockall, Child-Pugh) and differentiating IBD from IBS using faecal calprotectin. Focus on management algorithms for acute abdomen (e.g., cholecystitis vs. pancreatitis) and red-flag symptoms for malignancy. Expect several questions on H. pylori eradication, variceal bleeding, and jaundice workup. Do not memorise rare conditions; instead, drill common presentations and their evidence-based pathways.

Practise it: MedLumen has 50 Gastrointestinal System questions for the PLAB 1, each with a full explanation and references.