Short Bowel Syndrome

Short bowel syndrome (SBS) results from extensive resection of the small intestine (typically <200 cm of remaining small bowel in adults), leading to malabsorption of nutrients, fluids, and electrolytes. The normal small intestine is 300-800 cm. Common causes include: Crohn disease (most common in adults — repeated resections), mesenteric ischemia, volvulus, trauma, and necrotizing enterocolitis (most common in neonates). The severity depends on: length of remaining bowel, which segment was resected (jejunum vs. ileum — ileal resection is worse because the ileum has unique absorptive functions), presence of the ileocecal valve (slows transit and prevents bacterial migration), and whether the colon is preserved. The ileum specifically absorbs: bile acids (loss leads to bile acid malabsorption and steatorrhea), vitamin B12 (deficiency develops without ileum), and fat-soluble vitamins (A, D, E, K). Loss of the ileocecal valve allows colonic bacteria to migrate into the small bowel (bacterial overgrowth) and accelerates transit time. The colon serves as a 'salvage organ' — it can absorb water, electrolytes, and short-chain fatty acids from bacterial fermentation of unabsorbed carbohydrates, partially compensating for small bowel loss.