Crohn's disease may cause sores, or ulcers, that tunnel through the intestine and into the surrounding tissue, often around the anus and rectum. These abnormal tunnels, called fistulas, are a common complication of Crohn's disease. They may get infected. Crohn's disease can also cause anal fissures. These are narrow tears that extend from the muscles that control the anus (anal sphincters) up into the anal canal.
An anal fistula can often be treated with medicines. But sometimes surgery to repair the fistula may be needed. Conservative treatment with antibiotics and medicines to reduce pain and inflammation is usually tried before surgery. Surgery for an anal fistula sometimes does not heal well or takes a long time to heal. So it is usually done only if there is a complication such as an abscess.
Anyone with an unusual anal fistula that does not respond to conservative treatment should be examined for Crohn's disease. A fistula is often the first sign of Crohn's disease. An exam may include anoscopy or sigmoidoscopy. These are tests that allow a doctor to view the lower rectum and lower large intestine through a viewing scope. Complete evaluation may require sedation because the exam can cause discomfort.