An anal fissure is a longitudinal tear of the skin of the anal canal that extends from the dentate line to the anal verge. It is the most common cause of painful rectal bleeding. Fissures are thought to be caused by the passage of hard or large stools with constipation, but may also be seen with diarrhea. Incidence follows a bimodal distribution with fissures most commonly seen in infants and middle-aged adults. Patients present with intense sharp, burning pain during and after bowel movements. Pain may be accompanied by bright red blood. Gentle examination with separation of the buttocks usually provides adequate visualization. Anal fissures are typically a few millimeters wide and most commonly occur in the posterior midline where the skeletal muscle fibers encircling the anus are weakest.
Management and Disposition
Treat initially with supportive measures, including increased dietary fiber and fluids, sitz baths, topical analgesics such as lidocaine 2% jelly, and topical vasodilators such as nifedipine 0.2% ointment or nitroglycerin 0.2% ointment. Second-line therapies include topical diltiazem 2% gel as well as oral nifedipine or diltiazem. Most simple anal fissures resolve in 2 to 4 weeks, and surgical management is typically reserved for refractory cases.
Pain and involuntary sphincter spasm may preclude bedside digital or anoscopic examination, and anesthesia may be required for adequate evaluation.
An anal fissure off the midline should prompt consideration of secondary causes, such as inflammatory bowel disease, STI, or rarely leukemia, sickle cell disease, or anal neoplasm.
Anal fissures are the most common cause of painful rectal bleeding.
Anal Fissure. A typical anal fissure located in the posterior midline. (Photo contributor: Paul J. Kovalcik, MD.)
Anal Fissure. An anal fissure is seen at the superior midline in a patient with 2 weeks of constipation. (Photo contributor: Kevin J. Knoop, MD, MS.)
Anal Fissure. This adolescent patient complains of bloody, painful, hard stools and has an anal fissure in the midline toward the perineum. (Photo contributor: Lawrence B. Stack, MD.)