Anal Fistula

Diagnosis

A history of recurring anal abscess with drainage is a clue that a person may have an anal fistula. The external opening usually appears as a red, inflamed spot that oozes pus, sometimes mixed with blood.

The location of the external opening gives a clue to a fistula's likely path and sometimes the fistula can actually be felt as a hard cord. In many cases, however, visualizing its path may take various tools, and sometimes the path may not be clear until surgery.

Tools doctors may use include:

• Fistula probe. An instrument specially designed to be inserted through a fistula
• Anoscope. A small instrument to view the anal canal

If a fistula appears particularly complicated or in an unusual place, doctors may also use:

• Diluted methylene blue dye. Injected into a fistula
• Fistulography. Injection of a contrast solution into a fistula and then X-raying it
• Magnetic resonance imaging

To rule out other disorders such as ulcerative colitis or Crohn's disease, doctors may use:

• Flexible sigmoidoscopy. A thin, flexible tube with a lighted camera inside the tip allows doctors to view the lining of the rectum and sigmoid colon as a magnified image on a television screen
• Colonoscopy. Similar to sigmoidoscopy, but with the ability to examine the entire colon or large intestine