Background and Methods: Lateral internal sphincterotomy, the most common treatment for chronic anal fissure, may cause permanent injury to the anal sphincter, which can lead to fecal incontinence. We compared two nonsurgical treatments that avert the risk of fecal incontinence. We randomly assigned 50 adults with symptomatic chronic posterior anal fissures to receive treatment with either a total of 20 U of botulinum toxin injected into the internal anal sphincter on each side of the anterior midline or 0.2 percent nitroglycerin ointment applied twice daily for six weeks. Results: After two months, the fissures were healed in 24 of the 25 patients (96 percent) in the botulinum-toxin group and in 15 of the 25 (60 percent) in the nitroglycerin group (P=0.005). No patient in either group had fecal incontinence. At some time during treatment, five patients in the nitroglycerin group had transient, moderate-to-severe headaches that were related to treatment. None of the patients in the botulinum-toxin group reported adverse effects. Ten patients who did not have a response to the assigned treatment - 1 in the botulinum-toxin group and 9 in the nitroglycerin group - crossed over to the other treatment; the fissures subsequently healed in all 10 patients. There were no relapses during an average of about 15 months of follow-up. Conclusions: Although treatment with either topical nitroglycerin or botulinum toxin is effective as an alternative to surgery for patients with chronic anal fissure, botulinum toxin is the more effective nonsurgical treatment.
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