Rectal Intussusception

Rectal intussusception is the telescoping of the rectal wall into the lumen of the distal rectum or anal canal during defecation. It is the first stage in a spectrum that ends in full-thickness external rectal prolapse. It may involve the full thickness of the rectal wall or only the mucosa.

Pathology and classification

• Intrarectal (rectorectal): the fold stays in the rectum and does not reach the anal canal.
• Intra-anal (rectoanal): the fold passes into the anal canal.
• Depth and thickness are described as limited to the mucosa or involving the full wall. Higher-grade lesions (into the anal canal, thick-walled) correlate with symptoms.

Mechanism: weakness of the pelvic floor and rectal suspensory structures, repetitive straining, a deep pouch of Douglas, a redundant sigmoid, and lax rectal support allow the wall to invaginate. The lead point obstructs the evacuation of stool and causes a feeling of incomplete emptying. Repeated trauma to the leading edge produces a solitary rectal ulcer or a localized inflammation of the mucosa.

Epidemiology: seen in up to about 40 to 50% of asymptomatic people on defecography, so imaging findings must be matched to symptoms. It is more common in women, multiparous patients and those with a long history of constipation. Over time a minority progress to external prolapse. Complications: obstructed defecation, solitary rectal ulcer syndrome, fecal incontinence from sphincter stretching and rectal bleeding.

• Obstructed defecation: straining, a sense of incomplete emptying, digitation or vaginal splinting, and long toilet times
• Rectal pain, a feeling of a mass, mucus discharge and bleeding
• Soiling and fecal urgency in some
• Examination may show no abnormality, or an intraluminal fold on straining at proctoscopy
• Red flags: rectal bleeding with a change in bowel habit (exclude cancer), weight loss, anemia and sudden change in symptoms

1. Clinical assessment with digital rectal examination during straining, and proctoscopy.
2. Defecography (evacuation proctography or dynamic MRI) is the investigation of choice, showing the fold, its level, thickness and whether it descends into the anal canal, and any associated rectocele, enterocele or perineal descent.
3. Colonoscopy or flexible sigmoidoscopy to exclude a neoplasm and to examine for ulcer or inflammation.
4. Anorectal manometry and endoanal ultrasound for sphincter function and defects.
5. Colonic transit study with radio-opaque markers when slow transit is suspected.

Differentials: rectal prolapse, rectocele, solitary rectal ulcer, hemorrhoidal prolapse, rectal cancer, anismus, slow transit constipation, enterocele.

Management is by symptoms, with imaging used to confirm that the intussusception is the cause.

1. Conservative treatment for 3 to 6 months:
   • Psyllium husk 3.4 g (one sachet) orally twice daily with 250 mL of water, and macrogol 3350 17 g orally once daily.
   • Toilet training (avoiding straining and long toilet times, with foot support) and fluid intake over 1.5 litres a day.
   • Biofeedback therapy for dyssynergia, 6 to 12 sessions over 3 months.
   • Rectal evacuation aids (glycerin suppository 4 g PR once daily, or bisacodyl 10 mg PR once daily for up to 2 weeks).
2. Surgery for persistent symptoms after conservative treatment, with a high-grade lesion and a clear link between symptoms and the finding:
   • Laparoscopic or robotic ventral mesh rectopexy (the usual choice), with mesh fixed to the sacral promontory and anterior rectum, avoiding posterior dissection.
   • Resection rectopexy when constipation is severe and the sigmoid is redundant.
   • Perineal options (stapled transanal rectal resection, Delorme procedure) have a higher recurrence and are used in selected patients.
3. Prophylaxis: cefazolin 2 g IV as a single dose before incision (3 g if over 120 kg), with metronidazole 500 mg IV as a single dose, and enoxaparin 40 mg SC once daily for 7 days.
4. Outcomes: symptom improvement in 70 to 90% after ventral rectopexy. Complications are mesh erosion (about 1 to 2%), new constipation, sexual dysfunction, bleeding and recurrence.

Follow-up at 6 weeks, 6 months and 12 months. Counsel on avoiding straining.