Background: The aim of this prospective trial was to analyse the effectiveness and morbidity of chemical sphincterotomy in the treatment of chronic anal fissure after a 3-year follow-up.
Methods: One hundred consecutive patients with chronic anal fissures were treated by chemical sphincterotomy with 25 U botulinum toxin injected into the internal sphincter. Clinical and manometric results were recorded.
Results: No major complications were found; initial incontinence at the 2-month review (6%) spontaneously reversed at 6 months. There was a tendency of progressive recurrence over time, with an overall healing after 3 years of 47%. We found a group of patients with clinical (symptoms longer than 12 months and presence of a sentinel pile before treatment) and manometric factors (persistently elevated mean resting pressure, percentage of time with slow waves, and number of patients or percentage of time with ultra slow waves after treatment) associated with a higher recurrence of anal fissures.
Conclusion: Since it avoids the greater risk of incontinence associated with surgical sphincterotomy, we recommend the use of botulinum toxin as the first therapeutic approach for patients with chronic anal fissure and risk factors for incontinence; despite the higher rate of recurrence associated with this treatment. In patients with factors related to recurrence, re-injection with higher doses of botulinum toxin or complementary medical-surgical treatment should be considered.