A 72-year-old woman with advanced gastric cancer undergoes total gastrectomy with Billroth II reconstruction. On postoperative day 3, she is tolerating a liquid diet. On postoperative day 7, her serum albumin is 3.1 g/dL (preoperative 4.2 g/dL), hemoglobin is 9.2 g/dL (preoperative 11.5 g/dL), and serum iron is low. She complains of fatigue. Over the next 6 weeks, she is expected to lose an additional 5–10% of her body weight despite adequate oral intake. Which nutritional complication is she at highest risk for in the long term, and what is the primary mechanism?

Explanation

## Clinical Context Total gastrectomy removes the entire stomach, including the fundus where parietal cells reside. This patient is at risk for multiple nutritional deficiencies, but the question asks for the **highest long-term risk** and its mechanism. ## Why Vitamin B12 Deficiency Is the Correct Answer **Key Point:** Total gastrectomy removes all parietal cells, which produce intrinsic factor (IF). Without IF, vitamin B12 cannot be absorbed in the terminal ileum, leading to inevitable B12 deficiency over months to years. **High-Yield:** Vitamin B12 deficiency after total gastrectomy is: 1. **Inevitable** — occurs in 100% of patients without supplementation 2. **Delayed** — body stores last 3–5 years, so symptoms appear gradually 3. **Preventable** — requires lifelong IM or high-dose oral supplementation 4. **Serious** — causes megaloblastic anemia, peripheral neuropathy, and subacute combined degeneration (SCD) of the spinal cord if untreated **Mnemonic:** **PERNICIOUS** — Parietal cells lost → Intrinsic factor absent → B12 malabsorption → Neurological sequelae (paresthesia, ataxia, dementia) **Clinical Pearl:** B12 deficiency is the most common long-term nutritional complication after total gastrectomy. Patients require lifelong IM cyanocobalamin (1000 μg monthly) or oral high-dose cyanocobalamin (2000 μg daily). Serum B12 and methylmalonic acid should be monitored annually. ## Comparison of Post-Gastrectomy Nutritional Deficiencies | Deficiency | Mechanism | Timeline | Severity | Prevention | |-----------|-----------|----------|----------|------------| | **Vitamin B12** | Loss of intrinsic factor | 3–5 years | High (neurological) | IM/oral supplementation | | Iron deficiency | ↓ Gastric acid + ↓ IF for iron | Months–years | Moderate (anemia) | Oral iron, dietary counseling | | Calcium/Vitamin D | ↓ Gastric acid, ↓ fat absorption | Months–years | Moderate (osteoporosis) | Supplementation, dietary intake | | Protein-energy malnutrition | ↓ Gastric capacity, early satiety | Weeks–months | Variable | Small frequent meals, supplements | **Tip:** Early postoperative weight loss (5–10% over 6 weeks) is expected due to reduced capacity and dumping syndrome, but this is usually stabilized with dietary modification. B12 deficiency, however, is progressive and requires lifelong intervention. ## Why Other Options Are Suboptimal - **Iron deficiency anemia:** While iron deficiency does occur after gastrectomy (due to loss of gastric acid and reduced IF-mediated iron absorption), it is less severe and more manageable than B12 deficiency. Iron stores last 6–12 months, and oral iron supplementation is often effective. - **Protein-energy malnutrition:** This is common early postoperatively but usually stabilizes with small frequent meals, high-protein supplements, and dietary counseling. It is not the "highest long-term risk" compared to B12 deficiency. - **Hypocalcemia and fat-soluble vitamin malabsorption:** These are less common after total gastrectomy than after small bowel resection. Calcium absorption is impaired due to reduced gastric acid (which ionizes calcium), but this is manageable with supplementation and vitamin D. [cite:Sabiston Textbook of Surgery Ch 48; Harrison 21e Ch 297]