A 70-year-old man who underwent partial gastrectomy with Billroth II reconstruction 20 years ago presents with numbness of the feet, a sore tongue, and a hemoglobin of 8 g/dL with high mean corpuscular volume. Which mechanism best explains his anemia?

• A Iron malabsorption due to loss of the duodenal passage
• B Bacterial overgrowth in the afferent loop degrading vitamin B12 and binding intrinsic factor ✓
• C Autoimmune gastritis of the gastric remnant
• D Folate loss from shortened intestinal transit time

Explanation

Blind loop (afferent loop) syndrome arises when stasis allows bacterial overgrowth. Anaerobic bacteria deconjugate bile salts and consume or bind vitamin B12 before the ileum can absorb it, producing megaloblastic anemia and steatorrhea. The diagnostic clue is improvement with broad-spectrum antibiotics. Iron deficiency is the more common long-term problem after gastrectomy but causes microcytic anemia. Autoimmune gastritis causes pernicious anemia but is not related to the surgical anatomy here.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.