An anal fissure is a crack in the opening of the anus that causes pain, itching, and bleeding. Anal fissures are more common in infants and children and relatively uncommon in adults. Anal fissures can occur at any age. The pain is usually intense and usually occurs during or after a bowel movement. The most common cause of anal fissures is constipation, but diarrhea can also cause anal fissures. Anal fissures often form a vicious cycle: constipation causes fissures, and patients avoid defecation because of fissure pain, which in turn worsens constipation. Treatment includes dietary changes to avoid diarrhea or constipation, or topical medications to speed healing of the fissure. Symptoms and diagnosis The most common symptoms are pain during defecation and blood on the wipe. Acute fissures generally recover quickly. Chronic fissures are relatively difficult to treat and usually last more than 6 weeks. A physical examination by a doctor can easily detect anal fissures. Definitive diagnosis requires examination of the anal canal using anoscopy. Etiology Constipation can cause the skin around the anus to crack. Once it occurs, pain can cause the anal sphincter to spasm, resulting in decreased blood flow around the anus and slower healing of the fissure. Pain may also cause the patient to avoid defecation and worsen constipation. Other causes include diarrhea and Crohn’s disease. Treatment Home and over-the-counter medications for warm sitz baths, a high-fiber diet for constipation, fiber additives, and plenty of water. Over-the-counter creams include Vaseline gel, 5% lidocaine, or 2.5% plus 2.5% proparacaine, zinc oxide, or 1% hydrocortisone ointment. Second-line medications may be prescribed topical creams, including nitroglycerin, diltiazem, or nifedipine to relax the sphincter. Another treatment option is surgery, which can usually be performed on an outpatient basis. One surgical procedure involves local injection of botulinum toxin into the sphincter. Another is to sever a portion of the internal sphincter. These procedures can improve the blood flow to the anal fissure and reduce spasm. The surgery itself does not heal the fissure, but it is often effective in preventing recurrence.