Evacuation proctography in obstructed defaecation and rectal intussusception.

The symptoms of obstructed defaecation may present as a number of different syndromes including descending perineum, solitary rectal ulcer, irritable bowel and mucosal or complete rectal prolapse. In order to clarify the pathophysiology of obstructed defaecation we carried out dynamic and static radiological investigations together with manometric and electrophysiological measurements in ten patients with severe, intractable obstructed defaecation. Results were compared with a total of 35 control subjects. There were no significant differences in sphincter pressures or the recto-anal inhibitory reflex between patients and controls. Mean motor unit potential duration was prolonged in patients compared with controls (P less than 0.02) in the puborectalis and external sphincter indicative of neuropathic changes. X-ray measurements of the anorectal angle and perineal descent at rest showed no differences. However, obstructed defaecation patients had a greater increase in anorectal angle on straining (P less than 0.02) and significantly more descent on straining (P less than 0.002). Fast film sequence evacuation proctography showed that the anal canal was occluded by anterior rectal wall in four patients and five patients had variants of recto-rectal intussusception without overt rectal prolapse, which explained the obstructive symptoms. This information should allow the surgeon to follow a rational treatment programme based on the anatomical abnormality.