In chronic anal fissure, persistent hypertonia and spasm of the internal anal sphincter cause elevated internal pressures that prevent healing. A number of surgical procedures have been developed to eliminate spasm and allow the fissure to heal. Lateral internal sphincterotomy, the most popular current procedure, is associated with recurrence rates of less than 10 percent, but up to 66 percent of patients experience incontinence. Chemical agents that produce reversible reductions in sphincter pressure also can enhance healing of anal fissures. Arroyo and colleagues compared the effectiveness and morbidity of surgical (ambulatory open lateral internal sphincterotomy) and chemical (botulinum toxin type A [Botox] sphincterotomy) procedures in patients with chronic anal fissure.

The authors randomly assigned 80 consecutive patients with chronic anal fissure to surgical or chemical sphincterotomy. All patients had fibrous induration or exposed internal sphincter fibers despite at least six weeks of conservative medical treatment with high-residue diet, warm sitz baths, and analgesia. The authors performed detailed assessments on each patient to exclude other pathology (e.g., sexually transmitted disease, tuberculosis, pregnancy) or contraindication to the study treatments. All treatments were carried out by the same surgeon using standardized techniques. All patients received identical follow-up treatment instructions and were reevaluated at two, six, 12, 24, and 36 months after surgery. The follow-up assessment included physical examination, manometric assessment of anal pressure, and incontinence scoring.

The two groups were comparable in all significant areas at assignment to treatment. The mean age was 40 years, and symptoms typically had been present for 18 to 20 months. One patient in each group developed a hematoma, and one patient in the surgical group experienced bleeding. Otherwise, no complications were noted at the time of treatment. At one year, 37 (92.5 percent) of the surgical patients had healed compared with 18 (45 percent) patients treated with botulinum toxin. The only pretreatment variable significantly associated with non-healing was duration of symptoms. Mean resting pressures declined significantly in both groups after treatment, but a significantly greater number of patients treated surgically (32.7 versus 19.7 percent) experienced significant reductions in pressure. At two months, incontinence was reported by three (7.5 percent) of the patients treated with surgical sphincterotomy and by two (5 percent) of the patients treated with botulinum toxin. After one year, two patients in the surgical group reported occasional incontinence of flatus, but no incontinence was reported by any other patients.

The authors conclude that patients at high risk of recurrence of anal fissure because of duration of symptoms and pressure should be treated surgically. For other patients, botulinum toxin could be an initial therapy, especially patients older than 50 years and those at risk of developing incontinence.