Anal fistula

What are anal fistulas?

Anal fistulas are tubular, inflammatory connections between glands at the end of the digestive tract with the skin surface around the anal canal. These remnants from the developmental history are only slightly rudimentary in humans and were first described in 1880 by Herrman and Defosses. They are also called proctodeal glands.

Adults between 30 and 50 years old are particularly affected by anal fistulas, and men three times more likely than women. It occurs at about 8.6 per 100,000 people, so it is a fairly common disease.

Anal fistula: Causes of the disease

The glands, which are located at the transition from the rectum to the sphincter, are connected to the intestine through an excretory duct. When they become inflamed, it can lead to the formation of an abscess, which spreads in the direction of least resistance. It often runs between the inner and outer sphincters (intersphincteric) and eventually reaches the skin. Proctodeal glands are mainly in the back of the sphincter and therefore most anal fistulas are there. The anal abscess is surrounded by a membrane called the abscess capsule. The resulting connection to the outside is the actual fistula. Today, an anal abscess is considered to be the acute clinical disorder; a fistula is the chronic progressive form.

Nearly 90 percent of anal fistulas arise from proctodeal glands. Among the other causes, chronic inflammatory bowel diseases should be mentioned first. Especially patients with Crohn's disease can develop anal fistulas (5 to 40 percent), whereas anal abscesses are less common with ulcerative colitis. Other causes include bacterial infections (tuberculosis, actinomycosis), immunosuppressive diseases (HIV, leukaemia) and surgical treatments of the pelvic floor or vagina.

Anal fistula: Symptoms of the condition

Typically, the first sign of an anal fistula is a strong sensation of pain, followed by often purulent secretion from the fistula opening. In many cases, there is also fever and external signs of inflammation (redness, overheating, swelling, perforation). The disease extends to sepsis (blood poisoning). Sometimes the secretion stops. After a short while pressure builds up again, making itself felt through pain, and drops when the secretion comes out of the fistula opening.