What is a perianal cyst

Anal fistula

Causes & Symptoms

What are anal fistulas?

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

Anal fistulas particularly affect adults between the ages of 30 and 50, men three times more often than women. The incidence is around 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 muscle, are connected to the intestine via an excretory duct. If they become infected, an abscess may form and spread in the direction of least resistance. It often runs between the inner and outer sphincter muscles (intersphincteric) and eventually reaches the skin. Proctodeal glands are mainly located in the back of the sphincter system and therefore most anal fistulas are also found there. The anal abscess is surrounded by a membrane called the abscess capsule. The resulting connection to the outside is the actual fistula. Today the anal abscess is seen as the acute clinical picture, the fistula is the chronic form.

Almost 90 percent of anal fistulas arise from proctodeal glands. Among the other causes, chronic inflammatory bowel diseases should be mentioned first. Patients with Crohn's disease in particular can develop anal fistulas (5 to 40 percent), while anal abscesses are less common in ulcerative colitis. Other causes are bacterial infections (tuberculosis, actinomycosis), immunosuppressive diseases (HIV, leukemia) and surgical treatment of the pelvic floor or vagina.

Anal fistula: symptoms of the disease

Usually the first sign of an anal fistula is a feeling of severe pain, followed by an often purulent secretion from the opening of the fistula. In many cases there is also a fever and external signs of inflammation (reddening, overheating, swelling, perforation). The clinical picture extends to sepsis (blood poisoning). Sometimes the secretion stops again, after a short time pressure builds up again, which is noticeable in pain and which decreases when there is renewed secretion from the fistula opening.


Diagnosis: This is how we diagnose anal fistulas

Anal fistulas are initially diagnosed with simple means, namely by palpation and, if necessary, with a small probe. Sometimes the course of the fistula can be palpated as a strand. An internal opening of the fistula is already present in only one third of the cases in the acute stage of inflammation. Therefore, a proctological examination is required after about six weeks. In addition, transanal ultrasound is used (endosonography). In certain cases, an MRI (magnetic resonance tomography) examination is useful.