Botulinum toxin for the treatment of anal fistulae - a double blinded randomized trial

This is a blinded randomized trial of Botox injection with removal of the Seton drain and de- epithelialisation of the tract compared with Seton removal and de- epithelialisation alone for the treatment of complex anal fistulae. Dose of Botox: 2 X 40iU injections to the anal sphincters as a single administratio. This will be performed by the patient's treating surgeon. This procedure takes approximately thee minutes. Follow up will be done by a speicalist surgeon. The fistula will be judged to have healed (primary endpoint of the study) if the following criteria are met: • The external opening has healed. • The internal opening cannot be palpated on digital rectal examination. • The patient does not complain of any ongoing drainage from the fistula site.