Inflammatory Bowel Disease: Intestinal Problems (cont.)
Lori Kam, MD
Leslie J. Schoenfield, MD, PhD
Leslie J. Schoenfield, MD, PhD
Dr. Schoenfield served as associate professor of medicine and consultant in gastroenterology on the faculty of the Mayo Clinic for seven years. He became a professor of medicine in residence at UCLA from 1972 to 1999 (now emeritus). He was the director of gastroenterology at Cedars-Sinai Medical Center in Los Angeles for 25 years, where he received the chief resident's teaching award, the president's award, and the pioneer of medicine award.
In this Article
What kind of malabsorption occurs in IBD?
Malabsorption means abnormal intestinal absorption. Crohn's disease usually affects thesmall intestine, which is the part of the gut that absorbs most nutrients.Remember that Crohn's disease involves the small bowel and/or the colon, while ulcerative colitis involvesonly the colon. Crohn's disease of the upper part (duodenum) and middle part (jejunum) of thesmall intestine may interfere with the absorption of proteins, sugars, iron,vitamins, and fats. This widespread malabsorption in Crohn's disease, which does not occur in ulcerative colitis, may lead to weight loss and malnutrition. In addition, some unabsorbednutrients can cause the small or large intestine to secrete increased amounts ofliquid, which worsens the diarrhea in Crohn's disease. (As previously mentioned, diarrhea isthe most common symptom in patients with IBD, with or without the intestinalcomplications.) The lower end (ileum) of the small intestine is the part of thebowel most commonly involved in Crohn's disease. In ulcerative colitis, however, the function of the ileum isnormal. When the ileum is involved in patients with Crohn's disease (or surgically removed),a decreased absorption of vitamin B12 may occur. If a deficiency of B12develops, a particular type of anemia called pernicious anemia can result.
The ileum is also the major area for intestinal absorption of bile acids. The bileacids are compounds that are secreted in the bile by the liver into theduodenum. The major function of bile acids is to help transport and absorb fats,mostly in the jejunum. Bile acids that are not absorbed by a diseased or removedileum pass into the colon. The bile acids then induce the colon to secreteliquid, which aggravates the diarrhea. If the bile acids are not sufficientlyabsorbed in the colon and consequently become deficient, fat malabsorption andmore diarrhea can result.
Extensive Crohn's disease, usually involving the surgical removalof several intestinal segments over the years, can lead to a debilitatingcondition known as short bowel syndrome. In this condition, the patients havemany of the intestinal complications of Crohn's disease, including severe malabsorption. Theycan also suffer from the previously mentioned complications not directlyaffecting the intestinal tract (extraintestinal). Additionally, these patientsfrequently have certain other extraintestinal complications, such asosteoporosis (thin or porous bones), osteomalacia (soft bones), gallstones, andkidney stones.
How is malabsorption in IBD treated?
The treatment of malabsorption in patients with IBD includes medications totreat the underlying intestinal inflammation. Decreasing the inflammation canimprove the intestinal absorption of the nutrients that were malabsorbed. Themalabsorption or deficiency of B12 may need to be treated by administering thevitamin in the vein or into the muscle. Diarrhea that is induced by bile acidscan be treated with cholestyramine, a compound that works by binding the bileacids.
Supplemental calories and nutrients may be administered as special liquiddiets. These so-called elemental diets are composed of proteins, carbohydrates,vitamins, and fats that are broken down into smaller particles that are easierfor the intestine to absorb. Unfortunately, however, these diets often do notsmell or taste very good. Nevertheless, they can be administered through a smalltube inserted through the nose (enteral feeding). For patients who are unable totolerate any food or liquid by mouth or by enteral feeding, nutrition may needto be given solely through the veins (total parenteral nutrition). Finally, asmall bowel transplant can now be done for patients with severe Crohn's disease or otherwiseunmanageable short bowel syndrome.
Medically reviewed by Stephanie Hawthorne, MD; American Board of Internal Medicine with subspecialty of Gastroenterology
Medically Reviewed by a Doctor on 1/8/2014
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