November 27, 2015
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Inflammatory Bowel Disease: Intestinal Problems (cont.)

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What kind of malabsorption occurs in IBD?

Malabsorption means abnormal intestinal absorption. Crohn's disease usually affects the small 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 involves only the colon. Crohn's disease of the upper part (duodenum) and middle part (jejunum) of the small 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 unabsorbed nutrients can cause the small or large intestine to secrete increased amounts of liquid, which worsens the diarrhea in Crohn's disease. (As previously mentioned, diarrhea is the most common symptom in patients with IBD, with or without the intestinal complications.) The lower end (ileum) of the small intestine is the part of the bowel most commonly involved in Crohn's disease. In ulcerative colitis, however, the function of the ileum is normal. 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 B12 develops, a particular type of anemia called pernicious anemia can result.

The ileum is also the major area for intestinal absorption of bile acids. The bile acids are compounds that are secreted in the bile by the liver into the duodenum. 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 removed ileum pass into the colon. The bile acids then induce the colon to secrete liquid, which aggravates the diarrhea. If the bile acids are not sufficiently absorbed in the colon and consequently become deficient, fat malabsorption and more diarrhea can result.

Extensive Crohn's disease, usually involving the surgical removal of several intestinal segments over the years, can lead to a debilitating condition known as short bowel syndrome. In this condition, the patients hav emany of the intestinal complications of Crohn's disease, including severe malabsorption. They can also suffer from the previously mentioned complications not directly affecting the intestinal tract (extraintestinal). Additionally, these patients frequently have certain other extraintestinal complications, such asosteoporosis (thin or porous bones), osteomalacia (soft bones), gallstones, and kidney stones.

How is malabsorption in IBD treated?

The treatment of malabsorption in patients with IBD includes medications to treat the underlying intestinal inflammation. Decreasing the inflammation can improve the intestinal absorption of the nutrients that were malabsorbed. The malabsorption or deficiency of B12 may need to be treated by administering the vitamin in the vein or into the muscle. Diarrhea that is induced by bile acid scan be treated with cholestyramine, a compound that works by binding the bile acids.

Supplemental calories and nutrients may be administered as special liquid diets. These so-called elemental diets are composed of proteins, carbohydrates,vitamins, and fats that are broken down into smaller particles that are easier for the intestine to absorb. Unfortunately, however, these diets often do not smell or taste very good. Nevertheless, they can be administered through a small tube inserted through the nose (enteral feeding). For patients who are unable to tolerate any food or liquid by mouth or by enteral feeding, nutrition may need to be given solely through the veins (total parenteral nutrition). Finally, a small bowel transplant can now be done for patients with severe Crohn's disease or otherwise unmanageable short bowel syndrome.

Medically reviewed by Avrom Simon, MD; Board Certified Preventative Medicine with Subspecialty in Occupational Medicine


"Definition, epidemiology, and risk factors in inflammatory bowel disease"

Medically Reviewed by a Doctor on 5/26/2015


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