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Difficulty: HardGastroenterology and Hepatology

Match each gastrointestinal disorder to its primary underlying pathophysiological mechanism of malabsorption or characteristic histologic finding.

  • Whipple diseaseLamina propria infiltration by PAS-positive macrophages causing lymphatic obstruction
  • Celiac diseaseImmune-mediated villous atrophy and crypt hyperplasia decreasing the absorptive surface area
  • Small intestinal bacterial overgrowth (SIBO)Microbial deconjugation of bile salts leading to premature absorption and impaired micelle formation
  • Zollinger-Ellison syndromeInactivation of pancreatic digestive enzymes due to excessively low intraluminal pH
  • Terminal ileal Crohn diseaseImpaired active transport of conjugated bile acids in the distal small bowel depleting the enterohepatic pool

Answer

Whipple disease matches with lymphatic obstruction by PAS-positive macrophages; Celiac disease matches with immune-mediated villous atrophy; SIBO matches with microbial deconjugation of bile salts; Zollinger-Ellison syndrome matches with inactivation of pancreatic enzymes by acid; Terminal ileal Crohn disease matches with impaired active transport of conjugated bile acids.
Each disorder represents a distinct pathophysiological category of malabsorption: mucosal injury (Celiac disease), lymphatic obstruction (Whipple disease), altered luminal pH inactivating enzymes (Zollinger-Ellison syndrome), microbial alteration of bile salts (SIBO), and disruption of enterohepatic circulation (Terminal ileal Crohn disease).

Step-by-Step Solution

1
Analyze the mechanism for Whipple disease.
Tropheryma whipplei causes PAS-positive macrophage infiltration in the lamina propria.
These macrophages physically block lymphatic drainage in the lacteals, preventing chylomicron absorption.
2
Analyze the mechanism for Celiac disease.
Gluten sensitivity leads to immune-mediated mucosal damage characterized by villous atrophy.
The physical loss of absorptive surface area directly impairs the uptake of all nutrients.
3
Analyze the mechanism for Small intestinal bacterial overgrowth (SIBO).
Enteric bacteria deconjugate bile acids prematurely in the upper gut.
Deconjugated bile acids are rapidly absorbed in the jejunum instead of the ileum, preventing adequate micelle formation for fat absorption.
4
Analyze the mechanism for Zollinger-Ellison syndrome.
Massive amounts of gastric acid enter the duodenum.
Pancreatic enzymes (especially lipase) require a neutral or alkaline pH to function; the acid denatures them, preventing luminal fat digestion.
5
Analyze the mechanism for Terminal ileal Crohn disease.
Inflammation destroys the specialized transport mechanisms for conjugated bile acids in the terminal ileum.
Failure of the enterohepatic circulation depletes the bile acid pool, impairing micelle formation and fat absorption.

Key Concept

Pathophysiological Mechanisms of Malabsorption
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Topics

Gastroenterology and Hepatology

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