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.