Rectal Prolapse

Introduction and classification

Rectal prolapse is protrusion of the rectal wall through the anal canal. It is not common - the incidence in adults is roughly 2.5 per 100,000 per year - but it causes disproportionate distress, and it is a condition where the diagnosis is often delayed for years because patients are reluctant to describe the symptoms.

Three entities are grouped under the name, and distinguishing them is the first task.

Aetiology and risk factors

Full-thickness prolapse begins as an internal intussusception, usually starting about 6 to 8 cm above the anal verge. Repeated straining drives the intussusceptum progressively downwards until it emerges. A set of anatomical abnormalities is characteristically present, though whether they are cause or consequence is debated:

• An abnormally deep rectovesical or rectouterine pouch, allowing small bowel to press on the anterior rectal wall
• Loss of the normal posterior fixation of the rectum to the sacrum, so that the rectum is mobile
• A redundant sigmoid colon
• Diastasis of levator ani and a weak, patulous pelvic floor
• A patulous, low-pressure anal sphincter, often with pudendal neuropathy

Risk factors in adults

• Female sex and increasing age - although notably, many affected women are nulliparous, so it is not simply an obstetric injury
• Chronic constipation and straining at stool, the dominant behavioural factor
• Chronic diarrhoea, which is a less obvious but recognised association
• Previous pelvic or anorectal surgery, and previous obstetric injury
• Neurological disease - multiple sclerosis, spinal cord injury, cauda equina syndrome, previous stroke and dementia. A new prolapse with neurological symptoms deserves a neurological assessment.
• Chronically raised intra-abdominal pressure - chronic cough, chronic obstructive pulmonary disease, ascites, obesity
• Psychiatric illness and institutional care, both consistently over-represented, partly through constipating medication and immobility
• Connective tissue disorders

Risk factors in children

• Cystic fibrosis - prolapse occurs in a meaningful minority of children with CF, and a sweat test must be performed in any child with rectal prolapse
• Constipation and straining, and conversely acute diarrhoeal illness
• Malnutrition and severe wasting, which reduce ischiorectal fat and pelvic support
• Chronic cough, including pertussis
• Neurological disease such as spina bifida and myelomeningocele
• Parasitic infection, particularly Trichuris trichiura, worldwide

Clinical features

• A mass protruding from the anus, initially only on defaecation and reducing spontaneously, later on coughing, standing or walking, and finally permanently
• Faecal incontinence in 50 to 75% - the symptom patients find most disabling. It results from chronic stretching of the sphincter, continuous inhibition of the internal sphincter by the prolapsing bowel (the rectoanal inhibitory reflex held permanently open), and often coexisting pudendal neuropathy.
• Mucus discharge and perianal excoriation, from exposed rectal mucosa
• Bleeding, usually small volume from traumatised or ulcerated mucosa
• Constipation and obstructed defaecation in 25 to 50% - the prolapse itself obstructs the outlet, so patients strain harder and worsen it
• Tenesmus and a sensation of incomplete evacuation
• Pain is uncommon unless the prolapse becomes incarcerated or strangulated

Examination

1. Ask the patient to strain. The prolapse is often not visible on the couch. Examine in the left lateral position and, if nothing appears, ask the patient to strain while sitting on a commode - this is essential and is where the diagnosis is usually made.
2. Inspect the mucosal folds - concentric or radial - and estimate the length of prolapsed bowel
3. Palpate the prolapse between finger and thumb for a double thickness of wall
4. Digital rectal examination for sphincter tone, which is typically poor, and for squeeze pressure
5. Look for coexisting pelvic organ prolapse - cystocele, rectocele and uterine or vaginal vault prolapse are common companions, and a joint gynaecological assessment may be needed
6. Assess for a lead point - a rectal polyp or tumour can initiate an intussusception, so a mass must be excluded
7. Neurological examination including perianal sensation and anal tone where a neurological cause is suspected

Investigations

• Colonoscopy or flexible sigmoidoscopy - to exclude a tumour or polyp acting as a lead point, and to identify a solitary rectal ulcer or coexisting colorectal disease. Mandatory in adults.
• Defaecating proctography (evacuation proctography or MR defaecography) - the investigation of choice for internal intussusception and for mapping coexisting pelvic floor abnormalities such as enterocele, rectocele and perineal descent, which changes the operation planned
• Anorectal manometry - documents resting and squeeze pressures, quantifying sphincter dysfunction before surgery and helping predict whether continence will improve
• Endoanal ultrasound - identifies occult sphincter defects, particularly relevant in parous women
• Colonic transit studies - where severe constipation coexists, since a patient with slow-transit constipation may need a resection rather than rectopexy alone
• Sweat test for cystic fibrosis in every child with rectal prolapse
• Bloods - FBC for anaemia from chronic bleeding, and pre-operative workup

Management

Conservative measures

These are the whole of treatment in children and the foundation of it in adults.

• Treat constipation aggressively - fibre, fluid, bulk-forming and osmotic laxatives, and a review of constipating drugs
• Advise against straining and prolonged sitting on the toilet
• Pelvic floor exercises and biofeedback therapy, which improve both continence and evacuation and are often more effective than patients expect
• Barrier creams and skin care for perianal excoriation from mucus
• Teach manual reduction for a prolapse that recurs, so the patient can manage it themselves
• In children, treat the constipation, exclude cystic fibrosis, and reassure - the great majority resolve spontaneously by the age of four or five, and surgery is rarely required

Surgery in adults

Surgery is the only definitive treatment for full-thickness prolapse in adults. The choice is between an abdominal and a perineal approach, and it is driven by the patient's fitness for a general anaesthetic and laparotomy or laparoscopy rather than by the anatomy alone.¹

• Laparoscopic ventral mesh rectopexy has become the commonest abdominal operation in the UK. Dissection is anterior only, which avoids the autonomic nerves and reduces post-operative constipation compared with posterior rectopexy. NICE supports its use with standard arrangements for governance and audit.²
• Resection rectopexy adds a sigmoid resection and is favoured where there is a redundant sigmoid with significant constipation
• Delorme procedure strips a sleeve of mucosa from the prolapsed segment and plicates the underlying muscle, and suits shorter prolapses in frail patients
• Altemeier perineal rectosigmoidectomy resects the full thickness of the prolapsed bowel with a coloanal anastomosis, and is the operation of choice for an emergency gangrenous prolapse
• The PROSPER trial compared abdominal and perineal approaches and found no clear difference in quality of life or recurrence at the numbers recruited, which is one reason practice still varies and the decision remains individualised³

After surgery

Constipation must be managed lifelong, since straining is what caused the prolapse and will cause a recurrence. Continence often improves over 6 to 12 months as the chronically stretched sphincter recovers, so patients should be warned not to expect immediate resolution, and biofeedback should be offered where incontinence persists.

Complications

• Faecal incontinence, which may persist even after successful anatomical repair if the sphincter or pudendal nerves are permanently damaged
• Incarceration, strangulation and gangrene of the prolapsed segment
• Ulceration and bleeding of the exposed mucosa, and solitary rectal ulcer syndrome in internal intussusception
• Recurrence after any procedure, higher after perineal approaches
• Mesh complications after ventral mesh rectopexy - erosion into the rectum or vagina, infection and chronic pain. This is uncommon but has attracted appropriate scrutiny and must be discussed at consent.
• Anastomotic leak after resection rectopexy or Altemeier
• New or worsened constipation after posterior rectopexy, from autonomic nerve injury during posterior dissection
• Sexual dysfunction from hypogastric or pelvic nerve damage
• Skin breakdown and infection from chronic mucus discharge, and significant social isolation

Red flags

Prognosis

In children the outlook is excellent. Most cases resolve with treatment of the underlying constipation or diarrhoeal illness, and surgery is needed only in a small minority, usually those with an underlying neurological or structural problem.

In adults, surgery corrects the anatomy reliably, with recurrence rates under 10% after abdominal rectopexy and 10 to 25% after perineal procedures. The functional result is less predictable. Continence improves in roughly two thirds of patients, often gradually over the first year, but a substantial minority remain incontinent because the sphincter and pudendal nerves have been damaged beyond recovery.

That gap between anatomical and functional success is the point worth carrying away. A patient consented for rectopexy should be told that the prolapse will very probably be fixed, that incontinence will probably improve but may not, and that the improvement will take months rather than weeks. Managing that expectation is a large part of managing the condition.