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Difficulty: HardGastroenterology and Hepatology

Match each brief clinical presentation of chronic diarrhea to its most likely underlying etiology or pathogenesis.

  • A 45-year-old man with voluminous, watery diarrhea, profound hypokalemia (2.2 mEq/L), and absent gastric acid secretion on testingVasoactive intestinal peptide-secreting tumor
  • A 32-year-old woman with chronic diarrhea, iron deficiency anemia, and an intensely pruritic, papulovesicular rash on her elbows and kneesAutoimmune-mediated destruction of intestinal villi
  • A 24-year-old man with intermittent bloating and watery diarrhea characterized by a high stool osmotic gap (>125 mOsm/kg) and an acidic stool pHDeficiency of a brush border disaccharidase
  • A 55-year-old woman with episodic facial flushing, chronic watery diarrhea, and a right-sided systolic heart murmur that increases with inspirationExcessive secretion of serotonin by a neuroendocrine tumor
  • A 28-year-old healthcare worker with recurrent watery diarrhea whose colonoscopy reveals dark brown discoloration of the colonic mucosa with pale patchesSurreptitious ingestion of anthraquinone laxatives

Answer

The correct matches pair each specific clinical presentation of diarrhea with its exact pathophysiological mechanism: WDHA syndrome to VIPoma, dermatitis herpetiformis to celiac disease, high stool osmotic gap with acidic pH to lactase deficiency, flushing with right-sided heart murmur to carcinoid syndrome, and melanosis coli to laxative abuse.
Each clinical vignette provides pathognomonic features for a specific etiology of chronic diarrhea. VIPomas present with Watery Diarrhea, Hypokalemia, and Achlorhydria (WDHA syndrome). Celiac disease classically presents with malabsorption and dermatitis herpetiformis. Lactase deficiency causes an osmotic diarrhea characterized by a high stool osmotic gap and acidic stool pH due to bacterial fermentation of unabsorbed carbohydrates. Carcinoid syndrome typically involves episodic flushing, secretory diarrhea, and right-sided valvular lesions (like tricuspid regurgitation). Factitious diarrhea due to anthraquinone laxative abuse is classically identified by melanosis coli, a dark brown pigmentation of the colon.

Step-by-Step Solution

1
Analyze the first vignette focusing on diarrhea, profound hypokalemia, and achlorhydria.
Identified as WDHA syndrome.
These findings are the classic diagnostic triad for a VIPoma.
2
Examine the second vignette noting diarrhea, iron deficiency anemia, and a pruritic vesicular rash on extensor surfaces.
Identified as celiac disease presenting with dermatitis herpetiformis.
This rash is pathognomonic for gluten-sensitive enteropathy (autoimmune villous destruction).
3
Evaluate the third vignette noting a high stool osmotic gap and acidic stool pH.
Identified as an osmotic diarrhea due to carbohydrate malabsorption, such as lactase deficiency.
Unabsorbed lactose is fermented by gut flora into short-chain fatty acids, lowering the stool pH and increasing the osmotic gap.
4
Analyze the fourth vignette highlighting flushing, diarrhea, and a right-sided heart murmur.
Identified as carcinoid syndrome.
Excess serotonin causes right-sided valvular fibrosis (tricuspid regurgitation) and secretory diarrhea.
5
Review the fifth vignette describing a healthcare worker with dark brown colonic mucosa.
Identified as factitious diarrhea from laxative abuse.
Melanosis coli is a classic endoscopic finding of chronic anthraquinone laxative use.

Key Concept

Differential diagnosis of chronic diarrhea based on specific clinical and laboratory findings
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Topics

Gastroenterology and Hepatology

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