Managing Chronic Anal Fissure Pain. The most commonly used surgery is lateral internal sphincterotomy. After application of a topical anesthetic, if a patient can tolerate a gentle examination of the rectum with a finger and an anoscope can be inserted through the anus, enlarged hemorrhoids can be identified, and if present, treated with sclerotherapy. Learn which vitamins may help ease your constipation. An anal fissure is a small tear in the thin, moist tissue mucosa that lines the anus. The external anal sphincter is a voluntary muscle. As constipation can be a cause, making sure the infant is drinking enough fluids i.