The pathogenesis and pathophysiology of rectal prolapse and solitary rectal ulcer syndrome.

Rectal prolapse and solitary rectal ulcer syndrome are both benign conditions affecting the rectum, mainly in women; prolapse tends to occur late in life, while solitary rectal ulcer syndrome has a predilection for the younger adult. Complete rectal prolapse probably starts as a mid-rectal intussusception, although a combination of this theory and the 'sliding hernia' theory has been proposed by Altemeier et al (1971). The pelvic floor weakness associated with prolapse, which gives rise to incontinence, is most likely due to a traction injury to the pudendal nerve. Anorectal manometry will indicate those incontinent patients likely to benefit from rectopexy. Abnormal descent of the perineum may be found in rectal prolapse and solitary rectal ulcer syndrome as well as descending perineum syndrome per se. The clinical features of these three conditions can overlap. Solitary rectal ulcer syndrome is essentially due to prolapse and traumatization of the rectal mucosa. Inappropriate puborectalis contraction, abnormal perineal descent, and overt rectal prolapse have all been cited as possible mechanisms of development of the condition. Defecography is the radiologic investigation of choice. Electromyography, as in rectal prolapse, may show evidence of pudendal nerve damage although incontinence is rare.