Rectal prolapse

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Contents

Introduction

Rectal prolapse has been described at all ages. Peaks of incidence are observed in the fourth and seventh decades of life. In the Western adult population, females are much more commonly afflicted. About 20% of patients with prolapse have an associated history of psychiatric illness. The key to rectal prolapse and its treatment is to first understand the terminology (Definitions of rectal prolapse, Anatomic features of rectal prolapse.).

Ch29-fig1.jpg

Pathogenesis

The cause of rectal prolapse is unknown but abnormal motor activity of the pelvic floor muscles may play a central role. A number of anatomical and physiological abnormalities are noted but it is unclear whether these abnormalities are primary and causative or secondary to the prolapse.

The primary support of the rectum is the levator ani. The puborectalis pulls the rectum anteriorly and its muscle fibres intermingle with the external anal sphincter to provide further support. Anatomic features associated with prolapse include:

  • a deep peritoneal cul-de-sac
  • a long mesorectum and poor posterior fixation of the rectum
  • a redundant rectosigmoid
  • a lax and atonic levator ani.

In some cases, functional disturbances result from intense straining against a pelvic floor that does not relax concomitantly. This may lead to rectal wall intussusception, causing a sensation of incomplete evacuation leading to further straining. In response to chronic and prolonged straining when passing stools, the pelvic floor muscles become stretched. In turn, the perineum descends, stretching the pudendal nerve. Pudendal neuropathy further leads to denervation of the anal sphincters and puborectalis. Over time, and with continued straining, the rectum protrudes beyond the anal orifice (Anatomic features of rectal prolapse.). Faecal incontinence occurs in about 50% of patients and is caused both by progressive denervation of the external anal sphincter and by the presence of the intussuscepted rectum dilating the anal canal. Despite sphincter dysfunction, faecal incontinence is not invariably present.

About 40% of women presenting with rectal prolapse have had previous gynaecological surgery, such as hysterectomy. About 20% of female patients also have an associated uterine prolapse. This suggests that an anatomic abnormality of the pelvic floor may be contributory.

Clinical presentation

The clinical presentations and associated features of complete rectal prolapse are given in Box 29.2 Clinical presentation of complete rectal prolapse.

Differential diagnosis

Rectal prolapse can be difficult to distinguish from extensive prolapsing internal haemorrhoids. With rectal prolapse, concentric rings of mucosa line the prolapsed tissue and a sulcus is present between the anal canal and the rectum. Two layers of the rectal wall are palpated. Haemorrhoids are separated by radial grooves and the sulcus is absent.

Evaluation

History

Careful history is directed at establishing the duration of the prolapse, the presence of coexistent symptoms of faecal incontinence or constipation and the patient's general medical status.

Physical examination

Physical examination includes a full anorectal and sigmoidoscopic examination to evaluate the anal sphincters and to document any concomitant abnormalities in the rectum. If the rectal prolapse is not obvious, the patient is asked to strain on the toilet until the prolapse is reproduced and viewed by the examiner.

Colonoscopy

If there is rectal bleeding or any change in bowel habits, a full colonic evaluation with colonoscopy should be performed.

Defecating proctogram

If the diagnosis is not obvious and an occult rectal prolapse is suspected, a defecating proctogram is diagnostic.

Anorectal physiological assessment

Anorectal physiological assessment is not generally helpful in rectal prolapse but may be valuable in the assessment of patients with faecal incontinence, because it may sometimes influence the operative approach.

Colonic transit studies

Colonic transit studies may be useful in constipated patients.

Treatment

Surgery is generally indicated for the treatment of complete prolapse, except in the very elderly. Conservative management is generally prescribed initially for occult or mucosal rectal prolapse. Elastic-band ligation of the prolapsing anterior rectal mucosa is sometimes helpful. Patients with persistent and unacceptable symptoms are considered for surgery; the types of procedures are similar to those performed for complete prolapse.

A large number of operations have been described for complete prolapse. Evaluation of their respective effectiveness is often limited by short or incomplete post-operative follow-up, as the patients are often elderly. Recurrence of prolapse has been observed up to 10 years post-operatively. The choice of surgical operation for rectal prolapse depends on the patient's general medical condition and the presence of associated features, such as constipation, diverticular disease and faecal incontinence. In general, a transabdominal repair is used for younger patients and a perineal repair for the elderly and frail patients. A full mechanical bowel preparation and parenteral antibiotic prophylaxis are essential for minimising septic complications.

Abdominal approach

Sacral fixation/rectopexy

The rectum is mobilised postero-laterally down to the level of the coccyx. The lateral ligaments are preserved during lateral dissection. Anterior dissection is usually not necessary. Fixation of the rectum to the sacrum may be performed by non-absorbable sutures (suture rectopexy) or a synthetic mesh. A partial wrap using the synthetic mesh, leaving the anterior surface of the rectum free, is sometimes described as the modified Ripstein operation (Mesh rectopexy (modified Ripstein operation).). Complete recurrence is around 3%, although mucosal prolapse is more common. Post-operative constipation is a common complaint after a Ripstein operation, as a tight sling may obstruct defecation. Rectal mobilisation with division of lateral ligaments per se may result in constipation from disruption of rectal innervation.

Mesh rectopexy (modified Ripstein operation).

Abdominal sutured rectopexy with sigmoid resection (Frykman-Goldberg operation)

A sigmoid colectomy is performed. The rectum is mobilised as described earlier and sacral fixation with nonabsorbable sutures is performed. Resection of redundant rectosigmoid may reduce post-operative constipation, either by eliminating the potential for kinking above the sling, as in the Ripstein operation, or by shortening the colon. The recurrence rate is probably slightly lower than rectopexy alone. The complication rate, especially sepsis, is higher because of the associated sigmoid resection. This surgical option is best reserved for good-risk patients with severe constipation and rectal prolapse.

Faecal continence

Faecal continence improves post-operatively in about 50% of patients following either abdominal repair of rectal prolapse. Improvement in continence postoperatively is mainly due to improvement in resting anal pressure. Pre-operative resting pressure does not seem to be predictive of post-operative continence.

Perineal approach

Perineal proctosigmoidectomy (Altemeier operation)

The procedure may be performed under general or regional anaesthesia. Patients are placed in a prone ‘jack-knife’ position. A circumferential incision is made about 1 cm above the dentate line. The prolapsed rectum is unfolded and the redundant rectum transected. The mesorectum is serially ligated and divided to deliver redundant rectum through the anal opening. A coloanal anastomosis is then performed either by sutures or a circular stapler. The levator muscles may be approximated, constituting a ‘levatorplasty’, which may improve faecal continence. Some surgeons also plicate the anal sphincters. Post-operative care is the same as for any bowel anastomosis. Pain is minimal, which is a major benefit of the procedure. The most common early post-operative complications are anastomotic dehiscence or bleeding. The recurrence rate is commonly quoted as less than 10%, although longer follow-up suggests that the cumulative rate may be much higher. Constipation is rarely a problem.

Mucosal sleeve resection (Délorme's procedure)

The procedure is performed with the patient in a prone jack-knife or lithotomy position under local, regional or general anaesthesia. The submucosa is infiltrated with a 1:200 000 adrenaline solution. A circumferential incision is made at the level of the dentate line. Dissection is performed in the submucosal plane to the proximal extent of the prolapse. The redundant mucosa is then excised. The underlying rectal muscle wall is plicated and the mucosal defect is then closed by sutures. Supplemental plication of anal sphincters may be performed. The most common complication is postoperative bleeding from the denuded muscle surface. The operation is generally well tolerated by frail patients, although the recurrence rate is probably higher than in other procedures and faecal incontinence is not improved. This perineal approach is probably best for the smaller complete prolapse or mucosal prolapse because a perineal proctosigmoidectomy is technically difficult in these cases.

Occult prolapse

This starts as an infolding of the anterior rectal wall 6–8 cm from the anal verge. The prolapse may descend into the anal canal but not through the anus. About 40% of asymptomatic subjects have occult rectal prolapse and it is not clear whether these will invariably progress to a complete rectal prolapse. Common symptoms include sensation of obstructed or incomplete defecation, pelvic pain, rectal bleeding and faecal incontinence. Solitary rectal ulcer may be present. Some patients have underlying psychological abnormalities on formal testing.

The initial management is conservative with careful explanation of the condition to the patient. Medical management includes the use of bulk-forming agents and judicious use of suppositories or enemas. Biofeedback is effective if paradoxical contraction of the puborectalis muscle is identified by anorectal physiological studies. Elastic-band ligation of the redundant anterior rectal mucosa may provide short-term relief for constant urge to strain.

In refractory cases with severe symptoms, surgery may be considered. Surgical options are essentially the same as for overt prolapse. Symptomatic outcome is often unpredictable. Pre-operative symptoms may not have been due to the internal prolapse. Careful patient selection for surgical management is important.

Solitary rectal ulcer syndrome

Solitary rectal ulcer syndrome is an uncommon but distressing problem. It usually affects young adults, and is more common in women. Typically, patients present with passage of blood and mucus per rectum. While the bleeding is usually slight and intermittent, occasionally it is massive and may require transfusions. Some patients experience tenesmus and a feeling of rectal discomfort that is difficult for patients to describe. Many patients habitually strain when passing stools. Rectal prolapse, overt or occult, is present in about one-third of patients. In 25% of subjects, endoscopic and histological features of solitary rectal ulcer syndrome may be present without causing any symptoms.

While the clinical picture of solitary rectal ulcer syndrome may be diverse, its histological appearances are typical and include fibromuscular obliteration of the lamina propria with hypertrophy of the muscularis mucosa. Sometimes biopsy may show cysts caused by displaced but normal mucosa and the retention of mucus, which is often called ‘colitis cystica profunda’. The pathology is usually located anteriorly 5–8 cm from the dentate line, although it can be in any site within the rectum.

The solitary rectal ulcer may appear, macroscopically, as ulcerated, polypoid or hyperaemic. Multiple rather than solitary rectal lesions may be present. The ulcers, when present, tend to be shallow and grey in colour with a sharply demarcated and friable wall. The differential diagnosis includes cancer, lymphoma or Crohn's disease. It is important, therefore, to rely on the pathological features for a diagnosis of solitary rectal ulcer syndrome.

Pathogenesis

The aetiology of solitary rectal ulcer syndrome remains unknown. Trauma associated with rectal prolapse or self-digitation in the rectum is contributory in some patients. Anorectal physiological testing suggests that the puborectalis muscle fails to relax during straining in some, but not all, patients. This may result in abrasion of the anterior rectal wall against the contracted puborectalis muscle, resulting in ischaemia and ulceration.

Management

The rectal lesion must be biopsied to establish the diagnosis. Biopsy should be taken from the edge of the ulcer or from the polypoid lesion itself. A defecating proctogram is performed to detect occult prolapse and anorectal physiological testing to evaluate the pelvic floor.

Initially, the patient should be reassured that the condition is benign and the process should be explained. Conservative therapy with bulk laxative and re-education of bowel habit, such as avoidance of straining and biofeedback, leads to improvement or stabilisation of symptoms in 70% of patients. Symptoms may persist despite healing of the rectal lesion. Additional therapies include salazopyrine, steroid enema and sucralfate enema. None of these has been proven to show any additional benefit.

Unacceptable symptoms will persist in one-third of patients. Many of these have rectal prolapse, overt or occult. Ninety per cent of patients with rectal prolapse will improve following surgical repair of the prolapse. If no prolapse is noted, healing with surgical procedures is less reliable. Local excision of the rectal lesion is the simplest surgical procedure and may lead to improvement in symptoms, at least in the short term, in twothirds of patients. Rectopexy in the absence of rectal prolapse results in healing in only 25% of cases. Other surgical options include low anterior resection or a diverting stoma. Both are associated with a significant morbidity and the surgical outcome is unpredictable.

Solitary rectal ulcer syndrome is an interesting condition. More research into its pathogenesis is necessary to define the most appropriate therapy.
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