Long-term outcome of the use of botulinum toxin injection for functional anal pain

Aim Anal pain may occur in the absence of demonstrable anal pathology. Spasm of the sphincter muscles has been suggested as a cause in some patients. We aimed to assess the effectiveness of injection of botulinum toxin in treating this condition. Method Patients who had injection of botulinum toxin over a 3-year period were identified retrospectively. Patients were excluded if anal fissure or other organic pathology was found to account for their symptoms on examination under anaesthetic. Long-term outcome was assessed at a minimum 3-year post-procedure telephone follow up. Results Fourteen (eight male) patients were identified, of median age 50 years. Botulinum toxin (20-200 u) was injected into the internal sphincter. Seven of the 14 patients reported significant improvement in symptoms at 3 months. Seven were available for a structured telephone review at a median of 59 (42-68) months. The four patients who had benefited from the injection had remained asymptomatic. Conclusion Injection of botulinum toxin into the internal anal sphincter has a role in alleviating symptoms in a small proportion of patients with functional anal pain.