A 58-year-old man with a Billroth II gastrectomy performed 15 years ago presents with steatorrhea, abdominal distension, and a macrocytic anemia. Jejunal aspirate culture grows more than 10^5 colony-forming units/mL of coliforms. Which mechanism best explains his fat malabsorption?
- A Loss of pancreatic lipase secretion due to chronic pancreatitis
- B Bacterial deconjugation of bile salts producing unconjugated bile acids that precipitate at jejunal pH ✓
- C Extensive mucosal destruction of jejunal enterocytes by bacterial invasion
- D Impaired chylomicron formation from apolipoprotein B deficiency
Correct answer: B. Bacterial deconjugation of bile salts producing unconjugated bile acids that precipitate at jejunal pH
Explanation
In stagnant loop syndrome, bacteria deconjugate conjugated bile salts. Unconjugated bile acids have higher pKa and precipitate at the jejunal pH, so micelle formation fails and fat absorption falls. The same bacteria consume vitamin A12 and damage the brush border, causing the macrocytic anemia. Pancreatic function and apolipoprotein synthesis are intact here, and the mucosa is not invaded, which separates this from other steatorrhea causes.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.