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IM16.1-17 | Diarrheal Disorders — Graded Quiz
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A 45-year-old man with a 4-week history of bloody diarrhoea, weight loss of 5 kg, and nocturnal diarrhoea (waking from sleep) undergoes colonoscopy. Which feature of the history MOST strongly argues against irritable bowel syndrome (IBS) as the diagnosis?
Correct. Nocturnal diarrhoea that wakes the patient from sleep is a red flag sign that is virtually incompatible with IBS, which is a functional disorder driven by abnormal gut-brain interaction without structural disease. IBS symptoms typically do not occur during sleep. Nocturnal diarrhoea implies a genuinely organic process (IBD, infectious, microscopic colitis, neoplasm, autonomic neuropathy). Weight loss is also a red flag, but nocturnal symptoms are the most specific single feature against a functional diagnosis.
Red flags against IBS: nocturnal symptoms, rectal bleeding, unintentional weight loss, iron deficiency anaemia, family history of colorectal cancer/IBD, onset after 50. Any red flag mandates structural investigation before IBS can be diagnosed.
Nocturnal diarrhoea waking from sleep is the single strongest argument against IBS (a functional disorder) — organic disease is the only explanation for symptoms that interrupt sleep. Weight loss is also a red flag but is less specific (dehydration, anorexia can cause it in functional disease). IBS does not cause nocturnal symptoms.
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A 50-year-old woman presents with 3 months of foul-smelling pale stools that float, abdominal bloating, and a 7 kg weight loss. Anti-tissue transglutaminase (anti-tTG) IgA is strongly positive. She agrees to endoscopy. What is the EXPECTED histological finding in the duodenum that would CONFIRM the diagnosis and guide definitive management?
Correct. Coeliac disease (gluten-sensitive enteropathy) is confirmed on duodenal biopsy showing the Marsh classification changes: villous atrophy (flattening of villi), crypt hyperplasia (compensatory elongation of crypts), and increased intraepithelial lymphocytes (>25/100 enterocytes; Marsh III). Anti-tTG IgA is the screening antibody. Definitive management is strict lifelong gluten-free diet. Non-caseating granulomas = Crohn's disease; caseating granulomas = intestinal tuberculosis.
Coeliac disease diagnosis: anti-tTG IgA (screen) + duodenal biopsy (Marsh III = villous atrophy + crypt hyperplasia + intraepithelial lymphocytes). D-xylose absorption abnormal (proximal small bowel disease). Treatment = gluten-free diet lifelong.
Coeliac disease = villous atrophy + crypt hyperplasia + increased intraepithelial lymphocytes on duodenal biopsy (Marsh III). Confirmed by anti-tTG IgA serology + biopsy together. Treatment = strict lifelong gluten-free diet. Non-caseating granulomas = Crohn's; caseating = intestinal TB.
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A 32-year-old man has a 3-day history of watery diarrhoea with 8–10 episodes per day, mild abdominal cramping, and mild dehydration. He returned from a rural area 5 days ago. Stool culture grows a curved gram-negative rod that produces an enterotoxin and requires alkaline peptone water (pH 8.6) for selective isolation. Which antibiotic, if indicated, should be used as FIRST-LINE therapy in addition to rehydration?
Correct. Alkaline peptone water selective medium + curved gram-negative rod = Vibrio cholerae. The priority in cholera treatment is REHYDRATION (oral or IV depending on dehydration severity). Antibiotics shorten the illness duration but are secondary. For cholera, first-line antibiotic (when indicated — severe disease, to reduce duration and transmission) is doxycycline 300 mg single dose or tetracycline. Azithromycin (1 g single dose) is used in children and pregnant women. Ciprofloxacin is an alternative but resistance is emerging. Metronidazole is for protozoal infections.
Cholera treatment: (1) REHYDRATION — paramount (WHO Plan A/B/C). (2) Antibiotics (shorten duration): doxycycline 300 mg single dose (adult) or azithromycin 1 g (child/pregnant). Ciprofloxacin alternative. Zinc supplement for under-5s. Continue feeding.
Alkaline peptone water + curved gram-negative rod = Vibrio cholerae. Antibiotics shorten illness in cholera (secondary to rehydration). First-line: doxycycline 300 mg single dose (adults) or azithromycin (children/pregnant). Metronidazole has no role; ciprofloxacin is an alternative but resistance is rising.
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A 28-year-old woman with ulcerative colitis (UC) involving the entire colon is admitted with 8 bloody stools daily, fever 38.8°C, pulse 108/min, and haemoglobin 9.2 g/dL (baseline 12 g/dL). Her CRP is 85 mg/L. She is already on oral mesalazine. Abdominal X-ray shows colonic diameter of 7 cm with loss of haustrations but no perforation. Which of the following describes the IMMEDIATE management priority?
Correct. This is a severe acute attack of UC (Truelove-Witts criteria: >6 bloody stools/day + fever + tachycardia + anaemia). Colonic diameter ≥6 cm on plain X-ray is concerning for toxic megacolon (≥5.5 cm + systemic toxicity). Management: admit to hospital, IV hydrocortisone (100 mg every 6 hours or 400 mg/day) is the first-line treatment for severe UC. Daily abdominal X-rays monitor for toxic megacolon progression. If no response after 72 hours of IV steroids, escalate to rescue therapy (IV ciclosporin or infliximab) or emergency colectomy. Emergency colectomy without trialling IV steroids is not appropriate as first step unless there is perforation or peritonitis.
Severe UC (Truelove-Witts criteria): >6 bloody stools/day + any of: fever >37.8°C, HR >90, Hb <10.5, ESR >30. Management: admit + IV hydrocortisone 100 mg QDS. Day 3 assessment. No response: rescue therapy (ciclosporin/infliximab) or colectomy. UC colectomy = curative (unlike Crohn's).
Severe UC (Truelove-Witts: >6 bloody stools/day + fever/tachycardia/anaemia) requires hospital admission + IV hydrocortisone 100 mg QDS (not oral). Toxic megacolon surveillance (daily AXR) is mandatory. If no improvement in 72 hrs: rescue IV ciclosporin or infliximab, or colectomy. Mesalazine alone is insufficient for severe attacks.
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A 55-year-old man with Crohn's disease involving the terminal ileum presents with an acute exacerbation. He has also developed a perianal fistula. Which of the following is a recognised SURGICAL INDICATION in inflammatory bowel disease that is distinct from medical therapy failure?
Correct. Surgical indications in IBD include both emergency and elective categories. Emergency indications: (1) toxic megacolon with perforation or failure to respond to 72 hours of intensive medical therapy — peritonitis is an absolute surgical emergency; (2) massive haemorrhage; (3) perforation. Elective indications: stricture/obstruction, dysplasia/carcinoma, refractory disease. Perianal fistula is managed medically first (antibiotics, immunomodulators, anti-TNF agents like infliximab) before surgical consideration. Simple CRP elevation or ongoing diarrhoea on mesalazine alone is an indication to escalate medical therapy, not to operate.
IBD surgical indications — Emergency: toxic megacolon with peritonitis, perforation, massive haemorrhage. Elective: fibrostenotic stricture, colorectal dysplasia/cancer, growth failure (paediatric). UC colectomy = curative; Crohn's resection = non-curative (recurrence).
Surgical indications in IBD = toxic megacolon with peritonitis/perforation unresponsive to intensive therapy; massive haemorrhage; stricture/obstruction; dysplasia/carcinoma. Perianal fistula is first managed medically (infliximab, seton). Elevated CRP without complications = step-up medical therapy first.
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A 22-year-old student returns from 10 days in a rural area of Rajasthan with a 3-day history of non-bloody watery diarrhoea, nausea, and low-grade fever. His travel companion is similarly affected. Stool culture grows Salmonella typhi. Which of the following clinical features would prompt stool culture in this scenario?
Correct. Stool culture is NOT indicated for all cases of acute diarrhoea — most self-resolve in 3–5 days. Indications for stool culture include: high fever (>38.5°C) suggesting invasive bacterial infection; bloody or mucoid diarrhoea (dysentery); immunocompromised patients (HIV, transplant, chemotherapy); healthcare workers and food handlers; clinical features suggesting enteric fever (Salmonella); and severe or worsening illness after 5–7 days. Nausea/vomiting and mild self-limiting traveller's diarrhoea do not require culture.
Indications for stool culture: fever >38.5°C, bloody/mucoid stools, immunocompromised, healthcare/food-handler, persistent >7 days, severe illness, suspected Salmonella/Shigella/Campylobacter/E. coli O157:H7. Blood cultures: if enteric fever or bacteraemia suspected.
Stool culture indications: high fever (>38.5°C), bloody/mucoid stools (dysentery), immunocompromised host, food handler/healthcare worker, severe illness >5-7 days, suspected enteric fever. Routine mild self-limiting diarrhoea without these features does not require culture.
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A 10-year-old boy presents with profuse watery diarrhoea and vomiting for 18 hours. He appears ill: sunken eyes, no tears, dry mouth, very rapid breathing, and a weak radial pulse. Skin pinch retracts very slowly (>3 seconds). Which is the CORRECT immediate management?
Correct. Severe dehydration: sunken eyes, no tears, dry mouth, weak rapid pulse, skin pinch >3 seconds = signs of impending hypovolaemic shock. This requires WHO Plan C: IV Ringer's Lactate (or normal saline if RL unavailable) 100 mL/kg total — given as 30 mL/kg in the first 30 minutes (shock bolus), then the remaining 70 mL/kg over the next 2.5 hours (paediatric). In cholera, this corrects the acute fluid deficit. 5% dextrose is NOT appropriate (does not replace electrolytes; may worsen hyponatraemia). Oral hydration is contraindicated in severe dehydration with altered sensorium or shock.
Severe dehydration signs: lethargic/unconscious, sunken eyes, no tears, very dry mouth, skin pinch >3 sec, weak/no radial pulse. Treat with WHO Plan C: IV RL 100 mL/kg (30+70 mL/kg). Assess for oral resumption after stabilisation. Zinc 20 mg/day ×10-14 days for children <5.
Weak radial pulse + skin pinch >3 seconds + no tears + lethargy = severe dehydration / hypovolaemic shock. This requires IV Ringer's Lactate (Plan C): 30 mL/kg over 30 min, then 70 mL/kg over 2.5 hr (paediatric). Plan B ORS is for some dehydration; Plan C IV is for severe. 5% dextrose has no role — does not restore electrolytes.
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A 45-year-old man with a history of alcohol use presents with chronic diarrhoea for 2 months, predominantly night-time, with 4–5 oily stools per day. Serum folate and B12 are low. His endoscopy and stool culture are negative for infection. Hydrogen breath test is positive for small intestinal bacterial overgrowth (SIBO). Which investigation would BEST demonstrate the absorptive defect?
Correct. Oily/fatty stools (steatorrhoea) + nutritional deficiencies (folate/B12) + nocturnal diarrhoea + SIBO on breath test suggest malabsorptive diarrhoea. D-xylose absorption test is a functional test of small bowel absorptive capacity: D-xylose is absorbed by the small bowel mucosa without requiring pancreatic or biliary digestion. Abnormal D-xylose excretion in urine after oral ingestion indicates mucosal disease (e.g., coeliac, SIBO affecting mucosa). SIBO can cause B12 deficiency (bacteria consume it) and folate overproduction. Faecal calprotectin indicates bowel inflammation (IBD); it does not quantify absorption.
Investigations for chronic diarrhoea: faecal calprotectin (IBD marker), D-xylose test (small bowel absorption), colonoscopy + biopsy (microscopic colitis, IBD), capsule endoscopy (small bowel), serum folate/B12/iron (nutritional impact), hydrogen breath test (SIBO, lactose intolerance).
Steatorrhoea + nutritional deficiencies + SIBO = malabsorption. D-xylose test specifically assesses small bowel mucosal absorptive function. Faecal calprotectin indicates inflammation (IBD marker); colonoscopy with biopsy evaluates the large bowel mucosa. D-xylose test is the investigation of choice for demonstrating small bowel malabsorption.
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A 38-year-old woman with moderate Crohn's disease (CDAI 250) unresponsive to azathioprine and steroids is started on infliximab. Before initiating infliximab, which investigation is MANDATORY to rule out a contraindication specific to anti-TNF therapy?
Correct. Anti-TNF agents (infliximab, adalimumab) cause profound immunosuppression by blocking tumour necrosis factor-alpha, which is critical for granuloma formation and containment of latent tuberculosis. Latent TB reactivation is a major life-threatening complication of anti-TNF therapy, well-documented in India where TB prevalence is high. Before starting any anti-TNF agent, ALL patients must be screened for latent TB with TST (Mantoux) or interferon-gamma release assay (IGRA). If positive, a full course of isoniazid preventive therapy (IPT) must be completed before or concurrent with anti-TNF initiation. Hepatitis B screening is also required but the TB screen is the most specific and clinically critical check in the Indian context.
Anti-TNF pre-treatment screening: latent TB (TST/IGRA — mandatory, critical in India), Hepatitis B (HBsAg/anti-HBc), varicella immunity, CXR. Active TB = absolute contraindication. Latent TB = complete IPT first. NTEP: isoniazid preventive therapy 6H for latent TB contacts.
Before any anti-TNF therapy (infliximab/adalimumab), latent TB screening is MANDATORY — anti-TNF blocks the granuloma formation needed to contain latent TB. In India (high TB prevalence), TST/IGRA is critical. Latent TB reactivation is a major life-threatening risk. Hepatitis B screening is also required but TB screening is the most context-specific.
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A 65-year-old man with a 6-month history of altered bowel habits and rectal bleeding is found to have a 3 cm ulcerative lesion in the sigmoid colon on colonoscopy. Biopsy confirms adenocarcinoma. He undergoes sigmoid colectomy. In the postoperative period, he develops profuse watery diarrhoea (15 episodes/day), fever, and abdominal pain. Stool testing for Clostridioides difficile toxin A and B is positive. Which is the MOST appropriate first-line treatment?
Correct. Post-surgical antibiotic-associated profuse diarrhoea + positive C. difficile toxin = C. difficile infection (CDI). Current guidelines (IDSA 2021) recommend oral vancomycin (125 mg four times daily for 10 days) or fidaxomicin as first-line for all CDI episodes (not just severe). Oral metronidazole is no longer recommended as first-line due to lower cure rates. IV metronidazole does not reach adequate luminal concentrations for CDI treatment. Loperamide is ABSOLUTELY CONTRAINDICATED — slowing gut motility in CDI promotes toxin accumulation and increases risk of toxic megacolon. Ciprofloxacin can cause CDI but does not treat it.
C. difficile infection: oral vancomycin (125 mg QDS × 10 days) = first-line. Fidaxomicin alternative. Metronidazole only if vancomycin unavailable. Stop causative antibiotic if possible. Loperamide absolutely contraindicated. Severe CDI: IV metronidazole + oral vancomycin. Recurrent: fidaxomicin or faecal microbiota transplant.
C. difficile infection (CDI): oral vancomycin 125 mg QDS × 10 days (first-line per IDSA 2021) or fidaxomicin. Metronidazole is no longer first-line. Loperamide is absolutely contraindicated in CDI (promotes toxin accumulation, risk of toxic megacolon). IV antibiotics do not achieve adequate luminal levels for CDI treatment.
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A 40-year-old man presents with blood in stool for 8 weeks. Colonoscopy shows discrete deep ulcers in the terminal ileum, perianal fissures, and a 'cobblestone' appearance in the ascending colon; the rectum is spared. Histology shows non-caseating granulomas. CT scan reveals small bowel wall thickening. He now develops absolute constipation and vomiting, with X-ray showing dilated small bowel loops. Which complication has MOST LIKELY developed?
Correct. The clinical picture is unambiguously Crohn's disease: skip lesions, terminal ileum involvement, rectal sparing, cobblestoning, non-caseating granulomas, perianal disease. Crohn's disease causes transmural inflammation that leads to fibrostenotic stricture formation over time — the most common cause of small bowel obstruction in Crohn's. This is an ELECTIVE surgical indication (not an emergency unless perforation). Toxic megacolon is a complication of UC (or rarely Crohn's colitis), not small bowel Crohn's. The dilated small bowel loops + absolute constipation + vomiting = mechanical obstruction from stricture, not ileus.
Crohn's complications requiring surgery: fibrostenotic stricture (small bowel obstruction), fistula (enterovesical, enterocutaneous, enteroenteric), abscess, perforation, dysplasia/cancer. Crohn's surgery is NOT curative — recurrence is expected. Stricturoplasty conserves bowel length. Toxic megacolon = UC complication, not small bowel Crohn's.
Crohn's disease (skip lesions, terminal ileum, rectal sparing, non-caseating granulomas) + dilated small bowel + absolute constipation = fibrostenotic stricture causing mechanical small bowel obstruction. This is a surgical indication (resection of strictured segment). Toxic megacolon occurs in colonic disease (UC), not small bowel Crohn's.
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