Rectal Prolapse

Introduction

Rectal prolapse occurs when the full thickness of the rectal wall protrudes through the anal canal. This condition can cause discomfort, bleeding, and incontinence. Rectal prolapse is most commonly seen in older women, but it may occur in both sexes and at any age. Although the condition has fascinated surgeons for many years, the optimal surgical approach to rectal prolapse has not been determined. More than 100 surgical operations have been described, which can be grouped into perineal and abdominal approaches. Laparoscopic approaches have become common, with excellent functional results. Choice of the optimal repair for a patient involves many factors, including general health and bowel function. Constipation is reported in 30% to 67% of patients with rectal prolapse, and 60% to 80% have a history of incontinence.

Pathophysiology

The mechanisms by which prolapse occurs remain poorly understood. Brodén and Snellman suggested that prolapse is initiated by a midrectal intussusception, with its origin 8 to 10 cm inside the rectum. Chronic straining may be a precipitating factor, which might explain the association of prolapse with colitis cystica profunda and a solitary rectal ulcer. Another hypothesis relates prolapse and abnormal intestinal motility, such as that seen in slow-transit constipation.

Low anal resting pressures, which are frequently observed in patients with prolapse, may be caused by continuous rectoanal inhibition or by the dilating effect of the prolapse itself, with or without pudendal neuropathy. However, other investigators believe that an initial increase in external sphincter tone may cause a cycle of outlet obstruction, constipation, and straining. An impaired tolerance to distention, with reduced compliance and tone, may contribute to incontinence. Other features of patients with rectal prolapse include a deep pouch of Douglas, redundant sigmoid colon, deficient rectosacral fixation, weakness of the pelvic floor, and a patulous anus. Obviously it is difficult to determine which physiologic alterations are causative factors and which are a result of the progressive prolapse of the rectum.

Internal rectal intussusception, also called internal or hidden prolapse, occurs when the prolapse does not protrude through the anal orifice. This is often shown on defecography. Mucosal prolapse is diagnosed when the mucosa slides on the submucosa and protrudes into or through the anal canal. It is treated similarly to prolapsing internal hemorrhoids but is thought to predispose to true rectal prolapse.

Clinical Features

Rectal prolapse initially occurs only with defecation and straining, and patients are usually aware that it is happening. As the anus dilates and the rectal attachments loosen, the rectum may prolapse with the mildest straining, or even when the patient stands. Tenesmus, bleeding, and mucus discharge are common, and incontinence may range from mucus leakage to complete fecal incontinence. Some patients also report bladder and gynecologic dysfunction and may have prolapse of these organs. These patients are suitable for multidisciplinary assessment and management.

Upon physical examination, the anus may be patulous. Visual observation of everted bowel with concentric folds allows definitive diagnosis. If prolapse is not obvious, the patient should be examined while straining on the commode. Examinations with the patient in the left lateral or prone jackknife position often fail to reproduce the prolapse, and prolapse cannot be ruled out in this manner. Occasionally a prolapse is incarcerated, which requires the application of hypertonic sugar or honey to reduce edema and allow shrinkage and reduction. A small prolapse can be distinguished from prolapsing hemorrhoids by observing the concentric folds of the rectal wall, in contrast to the radial folds of the hemorrhoids. Digital examination also permits evaluation of sphincter tone and diagnosis of a rectocele.

Anoscopy is a good way to diagnose internal rectal intussusception. As the anoscope is gradually removed, the patient is asked to bear down and the prolapsing rectal mucosa or rectal wall can be seen descending toward the anus. Proctosigmoidoscopy facilitates examination of the rectal mucosa and allows one to check for an ulcer, a lead point, or additional disease. Most patients have already had a colonoscopy because of their age and the rectal bleeding often associated with their presentation.

The diagnosis of rectal prolapse is usually straightforward; however, the differential diagnosis includes hemorrhoids, prolapsing polyps, and anorectal neoplasia. Conditions such as a solitary rectal ulcer and colitis cystica profunda are often associated with rectal prolapse and present with similar symptoms.

Some persons advocate measuring colonic transit time in patients with constipation. We do not measure colonic transit time routinely, but only in patients with a history of severe constipation and associated sphincter weakness. Patients with chronic straining should undergo evaluation for paradoxical contraction of the puborectalis with anorectal physiologic testing or defecography, so that biofeedback may be instituted prior to repair of the prolapse. The clinical and financial value of routine preoperative studies, including anorectal manometry, pudendal nerve terminal motor latency, colonic transit studies, and defecography, is unclear. In most patients, an adequate history and physical examination should provide appropriate information to determine the correct operative approach.