Short Bowel Syndrome

The normal length of small bowel in an adult, starting from the duodenojejunal flexure, measures between 275 to 850 centimeters. Around 9 liters of fluid passes through the small bowel daily in the form of oral fluids, saliva, gastric, biliary, and pancreatic secretions. On average, about 7 liters of those fluids are absorbed in the small bowel and 2 liters in the large bowel. The large, healthy bowel absorbs roughly 150 kilocalories per day but can absorb up to 1000 kilocalories per day in those patients with malabsorption.

The absorption of most nutrients occurs in the first 100 centimeters of the jejunum. B12 and bile salts are absorbed in the last 100 centimeters of the ileum; magnesium is absorbed in the terminal ileum and proximal colon; water and sodium absorption occur throughout the bowel.

Short bowel syndrome (SBS) in adults is defined as less than 180 to 200 centimeters of remaining small bowel leading to the need for nutritional and fluid supplements. Although there is no accepted definition for SBS in children, the need for intravenous supplementation when having less than 25% of remaining small bowel that is expected for gestational age has been suggested.

About 75% of cases of SBS develop after a single, massive resection of bowel; whereas, the remaining 25% occur after multiple resections. Around two-thirds of patients who develop SBS survive their initial hospitalization, and a similar number survive their first year after developing SBS. Age and underlying disease primarily determine a patient's long-term outcome.