Rectal hyposensitivity is uncommon and unlikely to be the central cause of obstructed defecation in patients with high-grade internal rectal prolapse

Background There are several causes of obstructed defecation one of which is thought to be internal rectal prolapse. Operations directed at internal prolapse, such as laparoscopic ventral rectopexy, may improve obstructed defecation symptoms significantly. It is not clear whether the obstructed defecation with internal prolapse is a mechanical phenomenon or whether it results changes in rectal sensitivity. This study aimed to evaluate rectal sensory function in patients with obstructed defecation and high-grade internal rectal prolapse. Methods This study represents a retrospective review of a prospectively collected database of patients attending a tertiary referral pelvic floor unit. Patients with high-grade (recto-anal) intussusception formed the basis of this study. Rectal sensory function was determined by intrarectal balloon inflation. Three parameters (sensory threshold, urge to defecate and maximum tolerated volumes) were recorded. Abnormal sensitivity was defined as partial (one or two parameters abnormal) or total (all three abnormal). Key Results Four hundred and eight patients with high-grade internal rectal prolapse both with and without obstructed defecation symptoms were studied. Two hundred and forty one (59%) had normal sensation. Eighteen (4%) had total hyposensitivity and three (1%) total hypersensitivity. A further 96 (24%) had partial hyposensitivity whilst 50 (12%) had partial hypersensitivity. Neither hypersensitivity nor hyposensitivity differed between patients with and without symptoms of obstructed defecation. Conclusions & Inferences Rectal hyposensitivity is relatively uncommon in patients with high-grade internal rectal prolapse and obstructed defecation. Internal rectal prolapse may cause obstructed defecation through a mechanical process. It does not appear that rectal hyposensitivity plays a significant part in the pathological process.