The anal sphincter in idiopathic megarectum

PURPOSE: This study was designed to investigate the function and morphology of anal sphincters in patients with an idiopathic megarectum. METHOD: A total of 17 patients were studied by anal endosonography and manometry when not impacted. Fourteen had previously been manually disimpacted under general anesthetic, and three had not. RESULTS: Nine of 14 patients in the former group, but none of the latter group, had disruption of one or both anal sphincter muscles on endosonography. Endosonographic changes were characteristic of those identified previously in patients following anal dilation. Low anal resting pressure, indicative of internal sphincter dysfunction, was found in a substantial proportion of patients with either an endosonographically intact or disrupted internal anal sphincter. Voluntary contraction increment, a reflection of external sphincter function, was normal in all patients. CONCLUSION: Manual disimpaction under general anesthetic appears to be associated with iatrogenic structural injury to the anal sphincters. In some patients, this may contribute to sphincter weakness. This damage may contribute to the incontinence experienced by patients with a dilated rectum.