How do intestinal strictures form in IBD?
When inflammation is present for a long time (chronic), it sometimes can cause scarring (fibrosis). Scar tissue is typically not as flexible as healthy tissue. Therefore, when fibrosis occurs in the intestines, the scarring may narrow the width of the passageway (lumen) of the involved segments of the bowel. These constricted areas are called strictures. The strictures may be mild or severe, depending on how much they block the contents of the bowel from passing through the narrowed area.
Crohn's disease is characterized by inflammation that tends to involve the deeper layers of the intestines. Strictures, therefore, are more commonly found in Crohn's disease than in ulcerative colitis. Additionally, strictures in Crohn's disease may be found anywhere in the gut. Remember that the intestinal inflammation in ulcerative colitis is confined to the inner lining (mucosa) of the colon. Accordingly, in chronic ulcerative colitis, benign (not malignant) strictures of the colon occur only rarely. In fact, a narrowed segment of the colon in ulcerative colitis may well be caused by a colon cancer rather than by a benign (non-cancerous), chronic inflammatory stricture.
What are symptoms of intestinal strictures, and how are they diagnosed and treated?
Symptoms of internal strictures in IBD
Individuals may not know that they have an intestinal stricture. The stricture may not cause symptoms if it is not causing significant blockage (obstruction) of the bowel. If a stricture is narrow enough to hinder the smooth passage of the bowel contents, however, it may cause abdominal pain, cramps, and bloating (distention). If the stricture causes an even more complete obstruction of the bowel, patients may experience more severe pain, nausea, vomiting, and an inability to pass stools.
An intestinal obstruction that is caused by a stricture can also lead to perforation of the bowel. The bowel must increase the strength of its contractions to push the intestinal contents through a narrowing in the bowel. The contracting segment of the intestine above the stricture, therefore, may experience increased pressure. This pressure sometimes weakens the bowel wall in that area, thereby causing the intestines to become abnormally wide (dilated). If the pressure becomes too high, the bowel wall may then rupture (perforate). This perforation can result in a severe infection of the abdominal cavity (peritonitis), abscesses (collections of infection and pus), and fistulas (tubular passageways originating from the bowel wall and connecting to other organs or the skin). Strictures of the small bowel also can lead to bacterial overgrowth, which is yet another intestinal complication of IBD.
Internal strictures diagnosis in IBD
Intestinal strictures of the small intestine may be diagnosed with a small bowel follow-through (SBFT) X-ray. For this study, the patient swallows barium, which outlines the inner lining of the small intestine. Thus, the X-ray can show the width of the passageway, or lumen, of the intestine. Upper GI endoscopy (EGD) and enteroscopy are also used for locating strictures in the small intestine. For suspected strictures in the colon, barium can be inserted into the colon (barium enema), followed by an X-ray to locate the strictures. Colonoscopy is another diagnostic option.
Treatment of strictures in IBD
Intestinal strictures may be composed of a combination of scar tissue (fibrosis) and tissue that is inflamed and, therefore, swollen. A logical and sometimes effective treatment for these strictures, therefore, is medication to decrease the inflammation. Some medications for IBD, such as infliximab, however, may make some strictures worse. The reason is that these medications may actually promote the formation of scar tissue during the healing process. If the stricture is predominantly scar tissue and is only causing a mild narrowing, symptoms may be controlled simply by changes in the diet. For example, the patient should avoid high fiber foods, such as raw carrots, celery, beans, seeds, nuts, fiber, bran, and dried fruit.
If the stricture is more severe and can be reached and examined with an endoscope, it may be treated by stretching (dilation) during the endoscopy. In this procedure, special instruments are used through the endoscope to stretch open the stricture, usually with a balloon thatis passed through an endoscope. Once the balloon traverses the stricture, it is inflated and the force of the balloon dilates the stricture to a bigger size, thus opening the lumen to make it wider. If that doesn't work, some patients will require surgery. Typically, this procedure does not produce long-lasting results.
Surgery sometimes is needed to treat intestinal strictures. The operation may involve cutting out (resecting) the entire narrowed segment of bowel, especially if it is a long stricture. More recently, a more limited operation, called stricturoplasty, has been devised. In this procedure, the surgeon simply cuts open the strictured segment lengthwise and then sews the tissue closed crosswise so as to enlarge the width of the bowel's passageway (lumen). After surgery in Crohn's disease patients, medication still should be taken to prevent inflammation from recurring, especially at the site of the stricture. The reason for this recommendation is that after abdominal operations, recurrent intestinal inflammation is a common problem in Crohn's disease. Furthermore, the risk of post-operative intestinal fistulas and abscesses is increased in Crohn's disease patients. Therefore, only abdominal surgery that is absolutely necessary should be done in patients with Crohn's disease.