The treatment of internal anal sphincter achalasia with botulinum toxin.

Internal anal sphincter (IAS) achalasia is a disorder of defecation in which the IAS fails to relax. Botulinum toxin (BT), which has been successfully used to relax the anal and lower esophageal sphincters, was injected twice into the IAS of one adolescent and three infants with manometric, radiologic, and in 2 cases histochemical diagnosis of anal achalasia: in the adolescent a third injection was necessary. Spontaneous defecation was achieved in all patients following the second injection. In one case a diagnosis of short-segment Hirschsprung's disease was obtained after the second injection. Local infiltration of BT into the IAS proved effective in the treatment of IAS achalasia. Double-blind studies and longer follow-up periods are needed to better evaluate these preliminary results and define the limits of this promising therapy.