Botulinum toxin in the treatment of outlet obstruction constipation due to puborectalis syndrome

PURPOSE: Puborectalis syndrome has been difficult to treat. We investigated the efficacy of botulinum toxin in treating patients with puborectalis syndrome who had previously failed to respond to electromyographic biofeedback sessions and who refused to use anal dilators. METHODS: Of a group of 50 patients with chronic outlet obstruction constipation, four patients with puborectalis syndrome were included in the study. The patients were studied using anorectal manometry, defecography, and electromyography and then treated with 30 units of Type A botulinum toxin, injected into two sites on either side of the puborectalis muscle, under ultrasonographic guidance. RESULTS: One patient was lost to follow-up. After treatment in other patients, the frequency of natural bowel movements increased from zero to six per week and laxatives were needed by only one patient. Anorectal manometry demonstrated decreased tone during straining from (mean +/- standard deviation) 96.2 +/- 12 mmHg to 42.5 +/- 13 mmHg at four weeks (P = 0.003) and 63.2 +/- 22 mmHg at eight weeks (P = 0.009). Defecography performed eight weeks after treatment showed improvement in the anorectal angle, which increased from 94 +/- 11 degrees to 114 +/- 13 degrees (P = 0.01), and evacuation of barium paste. Electromyography demonstrated mild paradoxical contraction. However, 16 weeks after treatment one of these three patients suffered symptomatic recurrence. This patient was re-treated with 50 units of toxin; eight months later he required a further 60 units. Seven months after the last injection he reported normal daily bowel movements without the use of laxatives. CONCLUSIONS: Botulinum toxin injection should be considered as a simple therapeutic approach in patients with puborectalis syndrome. The use of higher dosage and a more precise method of toxin injections under transrectal ultrasonography account for the long-term higher success rate. However, because the effects of the toxin wear off within three months of administration, repeated injections could be necessary to maintain the clinical improvement.