Following total gastrectomy, a patient develops megaloblastic anaemia 3 years post-operatively. Serum B12 is 80 pg/mL. Schilling test (if available) would show malabsorption corrected by intrinsic factor. What is the mechanism and long-term management?
- A Dietary B12 deficiency; correct with oral B12 supplementation
- B Iron deficiency secondary to achlorhydria; give IV iron
- C Folate deficiency from reduced jejunal absorption; prescribe folic acid
- D Absent intrinsic factor secretion from gastric parietal cells; requires lifelong IM hydroxocobalamin injections ✓
Explanation
Total gastrectomy removes all parietal cells, which are the sole source of intrinsic factor (IF) — a glycoprotein essential for vitamin B12 absorption in the terminal ileum. Without IF, dietary B12 cannot be absorbed, leading to megaloblastic anemia with neurological complications (subacute combined degeneration of the spinal cord) if uncorrected. Since oral B12 absorption requires IF, lifelong IM or deep SC hydroxocobalamin (1 mg every 3 months) is required post-total gastrectomy. Iron deficiency is also common (due to loss of gastric acid which enhances ferric iron reduction), but the B12 deficiency mechanism is the key distinction for total gastrectomy.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
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