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A fistula is an abnormal passage, or tunnel, between two organs—called an internal fistula—or between an organ and the outside of the body—called an external fistula. In the lower GI tract, both internal and external fistulas can occur. Fistulas can develop during gestation or at any age after birth. Fistulas that develop during gestation are more common in boys than girls.

Fistulas may occur as a result of:

Symptoms of Fistulas

Some people with a fistula in the lower GI tract have no symptoms; others may experience:

People with any of these symptoms should be evaluated immediately by a health care provider.

Diagnosis and Treatment of Fistulas

External fistulas can be found during a physical examination. Internal fistulas can be seen during an upper or lower GI series, CT scan, or colonoscopy.

Colonoscopy. Colonoscopy is used to look inside the rectum and entire colon for signs of fistulas. Colonoscopy is performed at a hospital or outpatient center by a gastroenterologist or a radiologist. The health care provider will provide written bowel prep instructions to follow at home before the test. The person may be asked to follow a clear liquid diet for 1 to 3 days before the test. Laxatives and enemas may be used before the test.

For the test, the person will lie on a table while the doctor inserts a flexible tube into the anus. A small camera on the tube sends a video image of the intestinal lining to a computer screen. The doctor can see signs of fistulas. In most cases, a light sedative, and possibly pain medication, helps keep the person relaxed.

Cramping or bloating may occur during the first hour after the test. Driving is not permitted for 24 hours after the test to allow the sedative time to wear off. Before the appointment, people should make plans for a ride home. Full recovery is expected by the next day.

Internal and external fistulas may close on their own, although this process could take weeks or months. The doctor may prescribe antibiotics to prevent or treat infection resulting from leakage of intestinal contents. Some people may need to stop eating and receive nourishment intravenously to ensure proper healing.

If a fistula does not close on its own, a surgeon may perform intestinal resection surgery.

Reference: National Digestive Diseases Information Clearinghouse (NDDIC)