Prolapse of the rectum and anus
DEFINITION AND TYPES
Rectal prolapse is circumferential full-thickness protrusion of the rectal wall through the anal canal. Mucosal prolapse involves mucosa only. Internal prolapse (intussusception) remains within the rectum. Anal mucosal prolapse and prolapsing haemorrhoids are distinct conditions and must be differentiated clinically.
AETIOLOGY AND PATHOPHYSIOLOGY
Predisposing factors include pelvic floor weakness, laxity of supporting ligaments, deep pouch of Douglas, redundant sigmoid colon, chronic constipation, straining, childbirth, neurological disease and age-related tissue changes. Full-thickness prolapse may impair sphincter function and cause progressive incontinence; venous congestion can lead to oedema, ulceration and, rarely, strangulation.
CLINICAL FEATURES AND EXAMINATION
Patients report a protruding mass during defecation, mucus discharge, bleeding, perianal irritation, incomplete evacuation, constipation or faecal incontinence. Examine at rest and during straining; full-thickness prolapse typically has concentric circumferential folds, whereas prolapsing haemorrhoids have radial folds. Assess sphincter tone, perineum, constipation and pelvic floor function. If not visible, ask the patient to strain on a commode or use a photograph of the prolapse.
INVESTIGATIONS
Diagnosis is usually clinical. Colonoscopy is used to exclude a lead point, tumour or other colonic pathology, especially with bleeding or altered bowel habit. Defaecography or dynamic pelvic MRI may identify internal prolapse and associated pelvic floor disorders. Anorectal manometry and endoanal ultrasound are considered when incontinence or sphincter injury is relevant.
MANAGEMENT
Correct constipation with fibre, fluids, stool softeners and avoidance of straining; pelvic floor rehabilitation may help selected patients but does not reliably correct full-thickness external prolapse. In children, conservative management and treatment of precipitating factors are often successful. Adult full-thickness prolapse usually requires surgery. Abdominal approaches include rectopexy (suture or ventral mesh in selected cases) with or without sigmoid resection; perineal approaches include Delorme mucosal sleeve resection and Altemeier perineal rectosigmoidectomy. Choice depends on fitness, anatomy, constipation and continence. Incarcerated/strangulated prolapse requires urgent reduction or surgery.
COMPLICATIONS
Complications include ulceration, bleeding, oedema, incarceration, strangulation, necrosis, constipation and faecal incontinence. Recurrence and altered bowel function may occur after repair.