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Short Bowel Syndrome

by Atenodoro R. Ruiz, Jr., MD

Short bowel syndrome is a disorder causing diarrhea and poor absorption of nutrients (malabsorption), which often occurs after surgical removal of a large portion of the small intestine.

  • This disorder often occurs after a large part of the small intestine (usually two thirds of its length) is removed.

  • Diarrhea is the main symptom.

  • After surgery, people are given food and fluids by vein (intravenously).

  • Some people must continue the intravenous feedings for life.

  • Drugs such as loperamide and cholestyramine can help reduce diarrhea.

Common reasons for removing a large portion of small intestine are Crohn disease, a blockage of an artery that supplies blood to a large part of the intestine (mesenteric infarction), inflammation of the intestine caused by radiation (radiation enteritis), cancer, a twisted loop of intestine (volvulus), and birth defects.

Most digestion and absorption of food takes place in the small intestine. The consequences of removing a portion of the small intestine depend on how much is removed and its location. If the middle part (jejunum) is removed, sometimes the last part (ileum) can adapt and absorb more nutrients. If more than about 3 feet (about 1 meter) of ileum is removed, the remaining small intestine usually cannot adapt. Before adaptation occurs, or if it does not, the intestines have difficulty absorbing many nutrients, including fats, proteins, and vitamins. The intestines also cannot absorb bile acids secreted by the liver, which aid digestion.

Malabsorption causes diarrhea, typically beginning immediately after the surgery. Later, people develop undernutrition and vitamin deficiencies.

Treatment

Immediately after surgery, when diarrhea is typically severe, doctors give intravenous fluids to replace losses and usually also give intravenous feedings. These feedings, called total parenteral nutrition (TPN), contain all necessary nutrients, including proteins, fats, carbohydrates, vitamins, and minerals. As people recover and their stool output lessens, they are slowly given fluids by mouth.

The small intestine is about 12 to 21 feet (about 4 meters) in length. People who have had a large amount of small intestine removed (such as those with less than 3 feet [about 1 meter] of remaining jejunum) and those who continue to have excessive fluid losses require TPN for life. Others eventually tolerate food by mouth. The recommended diet usually has more fat and protein than carbohydrate. Small, frequent meals are better than fewer, large ones.

People who have diarrhea after meals should take antidiarrheal drugs such as loperamide 1 hour before eating. Cholestyramine can be taken with meals to reduce diarrhea caused by malabsorption of bile acid. Most people should take supplemental vitamins, calcium, and magnesium. Because people with short bowel syndrome often have excess stomach acid, most people also take an acid-blocking drug, such as a proton pump inhibitor. Some people require monthly injections of vitamin B 12 .

Small-intestine transplantation is an alternative for people who do not adapt to their short bowel and who cannot tolerate long-term TPN.

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