Perineal Descent Syndrome

Perineal descent syndrome is abnormal descent of the pelvic floor during straining, with the anorectal junction falling below the plane of the ischial tuberosities by more than 2.5 cm (and the resting position of the perineum is often low). It results from chronic weakness and stretching of the levator ani and the pelvic floor. It is one cause of both obstructed defecation and fecal incontinence.

Mechanisms

• Chronic excessive straining at stool, over many years
• Childbirth (multiparity, prolonged second stage, forceps)
• Stretch injury of the pudendal nerves (prolonged motor latency over 2.2 milliseconds) and pelvic floor denervation
• Chronic constipation, pelvic surgery, aging and connective tissue disorders

The syndrome is mostly in women over 50. Progressive descent leads to rectal intussusception, rectal prolapse, rectocele, enterocele and sphincter weakness, and the sequence is a vicious circle: descent causes difficulty evacuating, which causes more straining, which causes more descent. Complications: fecal incontinence, solitary rectal ulcer, rectal prolapse and urinary stress incontinence.

• Obstructed defecation with straining, incomplete emptying and need for digital assistance
• Fecal incontinence (urge or passive), soiling and urinary symptoms
• A sense of heaviness or a bearing-down sensation in the perineum, worse after standing and at the end of the day
• Perineal ballooning on straining, with the anal verge falling below the line of the ischial tuberosities
• Reduced anal tone and weak squeeze
• Red flags: rectal bleeding, change in bowel habit in older patients, severe neurological deficit, and cauda equina features

1. Clinical examination in the left lateral and standing positions with straining. Mark the position of the perineum with a perineometer.
2. Defecography (evacuation proctography or dynamic MRI): measurement of the descent of the anorectal junction (over 2.5 cm below the pubococcygeal line at rest or over 3 to 4 cm on straining), with rectal intussusception, rectocele and enterocele.
3. Anorectal manometry: reduced squeeze pressure and a blunted rectal sensation.
4. Pudendal nerve terminal motor latency (normal under 2.2 ms), and electromyography for denervation.
5. Endoanal ultrasound for sphincter defects.
6. Colonoscopy if bleeding or a change in bowel habit.

Differentials: rectal prolapse, rectal intussusception, solitary rectal ulcer syndrome, sphincter injury, slow transit constipation, cauda equina lesion.

1. Reduce straining:
   • Psyllium husk 3.4 g orally twice daily and macrogol 3350 17 g orally once daily.
   • Toilet posture with feet raised, and limiting toilet time to under 5 minutes.
   • Biofeedback therapy for dyssynergia, 6 to 12 sessions.
2. Incontinence with loose stool: loperamide 2 mg orally after each loose stool (maximum 16 mg a day), with a bowel diary.
3. Pelvic floor physiotherapy for 3 to 6 months, with electrical stimulation if available.
4. Surgery for symptomatic coexisting lesions:
   • Ventral mesh rectopexy or resection rectopexy for rectal prolapse or intussusception.
   • Repair of a significant rectocele or enterocele.
   • Sphincteroplasty for a defined anal sphincter defect (limited benefit in the presence of neuropathy).
   • Sacral neuromodulation (a temporary electrode for 2 weeks, then a permanent implant if there is a 50% or more reduction in incontinence episodes) for fecal incontinence.
   • 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.
5. Prevention: avoid chronic straining, maintain fiber and fluid intake over 1.5 litres a day, and use pelvic floor exercises after childbirth.
6. Outcomes: conservative treatment improves symptoms in about half. Surgery is less effective when pudendal neuropathy is severe, and perineal descent itself does not correct.

Follow-up at 3 months, 6 months and 12 months. Counsel that the aim is control of symptoms.