Intestinal Complications
of
Inflammatory Bowel Disease
Medical Author: Lori Kam, M.D.
Medical Editor: Leslie J. Schoenfield, M.D., Ph.D.
What are the intestinal complications of IBD?
Ulcerative colitis (UC) and Crohn's disease (CD) are known as the
inflammatory bowel diseases (IBD). The precise cause of IBD remains unknown.
These diseases are believed to be caused by a combination of genetic and
non-genetic, or environmental factors (for example, infections) that interact
with the body's immune (defense) system. When the intestinal immune system does
not function properly, many white blood cells accumulate in the inner lining (mucosa)
of the gut. The white cells then release chemicals that lead to tissue injury
(inflammation). This inflammation of the mucosa can cause diarrhea, which is the
most common symptom of ulcerative colitis and Crohn's disease, with or without the intestinal complications.
The intestinal complications of IBD occur when the intestinal inflammation is
severe, extends beyond the inner lining (mucosa) of the intestines, is
widespread, and/or is of long duration (chronic). For example, severe mucosal
inflammation can cause ulcers, bleeding, and toxic megacolon (a condition in
which the colon widens, or dilates, and loses its ability to properly contract).
Inflammation that extends beyond the inner lining and through the intestinal
wall is responsible for strictures (scarring that causes narrowing of the
intestinal wall) and fistulas (tubular passageways originating from the bowel
wall and connecting to other organs or the skin). Strictures, in turn, can lead
to bacterial overgrowth of the small intestine (SIBO). If the inflammation of
the small bowel is widespread, malabsorption of nutrients can be a complication.
Chronic inflammation can also be associated with colon cancer.
The majority of
IBD patients experience periods during which their disease intensifies (flares)
or subsides (remissions). Although most patients require medication for IBD,
they are able to live normal, productive lives. Some patients, but certainly not
all, will develop intestinal complications of IBD. When these complications
occur, they should be recognized and usually treated. Some patients with IBD
develop complications outside of the intestine (extraintestinal), such as
certain kinds of arthritis, skin rashes, eye problems, and liver disease. These
extraintestinal complications are discussed in other articles on IBD.
This
review will describe the various types of intestinal complications that are
associated with IBD, and will also summarize methods for their diagnosis and
treatment. Please note that the terms bowel, intestine, and gut are used
synonymously. The small bowel, or intestines, includes from top to bottom, the
duodenum, jejunum, and ileum. The large bowel is also called the colon.
Are the intestinal complications of ulcerative colitis and Crohn's disease different?
Some intestinal complications of
IBD occur in both ulcerative colitis and Crohn's disease. For example, ulceration of the inflamed inner
intestinal lining (mucosa), which causes abdominal pain and intestinal bleeding,
may complicate both diseases. Since both ulcerative colitis and Crohn's disease involve the colon,
complications that are associated with the colon, such as toxic megacolon and
colon cancer, occur in both diseases. Additionally,
there are no intestinal complications that occur only in ulcerative colitis and not in
Crohn's disease. On
the other hand, certain intestinal complications of IBD occur predominantly in
Crohn's disease (for example, fistulas) or exclusively in Crohn's disease and not in
ulcerative colitis (for example,
malabsorption and SIBO).
The differences in intestinal complications between ulcerative colitis
and Crohn's disease depend on the characteristically dissimilar behaviors of the inflammation
associated with these diseases. In Crohn's disease, the inflammation usually extends from the
inner lining (mucosa) through the entire thickness of the bowel wall. This
spreading inflammatory process may thereby lead to fistulas, abscesses, or
strictures of the bowel. By contrast, the inflammation in ulcerative colitis is limited to the
inner lining of the colon. The development of these particular complications is,
therefore, much less common in ulcerative colitis. Also, Crohn's disease can affect any area of the GI tract
from the mouth to the anus, whereas ulcerative colitis is limited to the colon. Therefore,
complications involving the small intestine, such as malabsorption and SIBO, as
previously noted, occur only in Crohn's disease and not in ulcerative colitis.
Next: Do intestinal ulcers occur in IBD? »
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