Rectal Prolapse 

Rectal prolapse was described as early as 1500 BC.

Three different clinical entities are often combined and called rectal prolapse: full-thickness rectal prolapse, mucosal prolapse, and internal prolapse (internal intussusception). Treatment of these 3 entities differs.

Full-thickness rectal prolapse is the most commonly recognized type and is defined as protrusion of the full thickness of the rectal wall through the anus. This is illustrated in the images below.

In mucosal prolapse, only the rectal mucosa (not the entire wall) protrudes from the anus.

Internal intussusception may be a full thickness or a partial rectal wall disorder, but the prolapsed tissue does not pass beyond the anal canal and does not pass out of the anus. Most of this article focuses on full-thickness rectal prolapse, which will be referred to as rectal prolapse.

Frequency

Rectal prolapse is uncommon; however, the true incidence is unknown because of underreporting, especially in the elderly population. Peaks in occurrence are noted in the fourth and seventh decades of life, and most patients (80-90%) are women.

The condition is often concurrent with pelvic floor descent and prolapse of other pelvic floor organs, such as the uterus or the bladder. Although multiple pregnancies are often implicated in the etiology, 35% of patients are nulliparous. A small subset of children is affected, usually before the age of 3 years. Evaluation and treatment of children with rectal prolapse is different from that for adults and is not addressed in this article.

The etiology of rectal prolapse is unknown, but it is often associated with long-standing constipation. Other predisposing conditions include chronic straining during defecation, pregnancy, previous surgery, and neurologic disease. The pathophysiology of rectal prolapse is also not completely understood or agreed upon.

The 2 main theories are essentially different ways of expressing the same idea.

The first theory postulates that rectal prolapse is a sliding hernia through a defect in the pelvic fascia. The second theory holds that rectal prolapse starts as a circumferential internal intussusception of the rectum beginning 6-8 cm proximal to the anal verge. With time and straining, this progresses to full-thickness rectal prolapse, although some patients never progress beyond this stage.

Certain anatomic features found during surgery for rectal prolapse are common to most patients. These features include a patulous or weak anal sphincter with levator diastasis, deep anterior Douglas cul-de-sac, poor posterior rectal fixation with a long rectal mesentery, and redundant rectosigmoid. Whether these anatomic features are the cause or result of the prolapsing rectum is not known.^[1]

Mucosal prolapse most likely has a different etiology and pathophysiology than full-thickness rectal prolapse and internal intussusception.^[2] Mucosal prolapse occurs when the connective tissue attachments of the rectal mucosa are loosened and stretched, thus allowing the tissue to prolapse through the anus. This often occurs as a continuation of long-standing hemorrhoidal disease and is treated as such.

Patients with rectal prolapse report a mass protruding through the anus. Initially, the mass protrudes from the anus only after a bowel movement and usually retracts when the patient stands up. As the disease process progresses, the mass protrudes more often, especially with straining and Valsalva maneuvers such as sneezing or coughing. Finally, the rectum prolapses with daily activities such as walking and may progress to continual prolapse.

As the disease progresses, the rectum no longer spontaneously retracts, and patients may have to manually replace it. This condition may then progress to a point at which the rectum prolapses immediately after being replaced and is continuously prolapsed. Rarely, the rectum becomes incarcerated, and patients cannot re-place the rectum.

Pain is variable. Ten to 25% of patients also have uterine or bladder prolapse, and 35% may have an associated cystocele.

In addition to a protruding mass from the anus, patients often report fecal incontinence. Incontinence occurs for 2 reasons.

First, the anus is dilated and stretched by the protruding rectum, disrupting the function of the anal sphincter. Second, the mucosa of the rectum is in contact with the environment and constantly secretes mucus, thus making the patient appear to be chronically wet and incontinent.

Patients with mucosal prolapse have similar problems but not to the same degree. Patients with internal intussusception often report difficulty with defecation and a sensation of incomplete evacuation.

Rectal prolapse is a clinical diagnosis that physicians should be able to confirm in the office. The patient is asked to sit on a toilet and strain, after which the rectum should prolapse. If it does not prolapse with just straining, the administration of a phosphate enema usually produces the prolapse. In a small child, a glycerin suppository can be used instead.

The protruding mass should show concentric rings of mucosa, which are classic signs of rectal prolapse. In cases of small prolapse, it is sometimes difficult to distinguish between mucosal and full-thickness rectal prolapse. Mucosal prolapse typically exhibits radial folds instead of concentric rings. If these cannot be clinically distinguished, a defecogram may be of help in differentiating these 2 conditions. A defecogram is unnecessary in the presence of an obvious rectal prolapse.

A detailed history to evaluate incontinence and/or constipation is important, as it plays a role in determining the appropriate surgical procedure.

For excellent patient education resources, visit eMedicine's Esophagus, Stomach, and Intestine Center. Also, see eMedicine's patient education article Rectal Prolapse.

The existence of rectal prolapse is an indication for surgery.

• Rectum: The rectum is the distal 12-15 cm of the large intestine between the sigmoid colon and the anal canal. It primarily serves as a reservoir for fecal material.
• Mucosa: This is the inner lining of the intestinal tract.
• Internal anal sphincter: The internal anal sphincter is a smooth muscle that is the most distal extension of the inner circular smooth muscle of the colon and the rectum. It is 2.5-4 cm long and normally 2-3 mm thick. The internal sphincter is not under voluntary control and is continuously contracted to prevent unplanned loss of stool.
• External anal sphincter: The external anal sphincter is striated muscle that forms a circular tube around the anal canal. Moving proximally, it merges with the puborectalis muscle and the levator ani to form a single complex. Control of the external anal sphincter is voluntary.
• Dentate line: The dentate line is the junction of the ectoderm and endoderm in the anal canal.

Contraindications to surgical correction of rectal prolapse are based on the patient's comorbidities and his or her ability to tolerate surgery.