Short bowel syndrome is malabsorption resulting from extensive resection of the small bowel (usually more than two thirds the length of the small intestine). Symptoms depend on the length and function of the remaining small bowel, but diarrhea can be severe, and nutritional deficiencies are common. Treatment is with small feedings, antidiarrheals, and sometimes total parenteral nutrition or intestinal transplantation.
Short bowel syndrome is a malabsorption disorder.
Common reasons for extensive resection are Crohn disease, mesenteric infarction, radiation enteritis, cancer, volvulus, and congenital anomalies.
Because the jejunum is the primary digestive and absorptive site for most nutrients, jejunal resection leads to loss of absorptive area and significantly reduces nutrient absorption. In response, the ileum adapts by increasing the length and absorptive function of its villi, resulting in gradual improvement of nutrient absorption.
The ileum is the site of vitamin B12 and bile acid absorption. Severe diarrhea and bile acid malabsorption result when > 100 cm of the ileum is resected. Notably, there is no compensatory adaptation of the remaining jejunum (unlike that of the ileum in jejunal resection). Consequently, malabsorption of fat, fat-soluble vitamins, and vitamin B12 occurs. In addition, unabsorbed bile acids in the colon result in secretory diarrhea. Preservation of the colon can significantly reduce water and electrolyte losses. Resection of the terminal ileum and ileocecal valve can predispose to small intestinal bacterial overgrowth.
Treatment of Short Bowel Syndrome
Total parenteral nutrition (TPN)
Eventual oral feeding if > 100 cm of small bowel remain
In the immediate postoperative period, diarrhea is typically severe, with significant electrolyte losses. Patients typically require TPN and intensive monitoring of fluid and electrolytes (including calcium and magnesium). An oral iso-osmotic solution of sodium and glucose (similar to the World Health Organization's oral rehydration formula—see Oral Rehydration) is slowly introduced in the postoperative phase once the patient stabilizes and stool output is < 2 L/day.
Patients with extensive resection (< 100 cm of remaining small bowel) and those with excessive fluid and electrolyte losses require TPN for life.
Patients with > 100 cm of remaining jejunum can achieve adequate nutrition through oral feeding. Fat and protein in the diet are usually well tolerated, unlike carbohydrates, which contribute a significant osmotic load. Small feedings reduce the osmotic load. Ideally, 40% of calories should consist of fat.
Gastric acid hypersecretion can develop, which can deactivate pancreatic enzymes; thus, most patients are given proton pump inhibitors.
Small-bowel transplantation is advocated for patients who are not candidates for long-term TPN and in whom adaptation does not occur.
Key Points
Extensive resection or loss of small bowel can cause significant diarrhea and malabsorption.
Patients with < 100 cm of remaining jejunum require lifelong total parenteral nutrition; patients with > 100 cm of remaining jejunum may survive on small feedings that are high in fat and protein and low in carbohydrate.
