Bilateral versus posterior injection of botulinum toxin in the internal anal sphincter for the treatment of acute anal fissure.

AIM Comparison of bilateral versus posterior injection of botulinum toxin into the internal anal sphincter for treatment of acute anal fissure. METHODS Forty patients with acute anal fissure were randomly divided into two equal groups. Group 1 was treated by injecting 20 units of botulinum toxin into each side of the internal anal sphincter, and group 2 by injecting 25 units of botulinum toxin into the midline posteriorly. RESULTS The mean time to pain relief was 8.45 (standard deviation (SD) 7.41) days in group 1 and 7.20 (SD 7.19) days in group 2. Healing took place in a mean of 5.20 (SD 1.85) weeks in group 1 and 5.40 (SD 2.01) weeks in group 2. Fissures failed to heal in 2 patients in group 1 and 3 in group 2, and recurred in 4 patients in group 1 and 3 in group 2. CONCLUSION Botulinum toxin injection is effective in treating acute anal fissure. A single posterior injection is easier and less painful than bilateral injection, and is as effective in pain relief.