Anal Incontinence
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Direct answer
Urge incontinence — the patient senses the call but cannot hold it — points to external sphincter or pelvic floor weakness, while passive soiling without warning points to internal sphincter failure or overflow; separating the two patterns at the bedside narrows the cause faster than any investigation. In women the dominant cause is obstetric trauma: a third or fourth-degree perineal tear, forceps delivery or prolonged second stage that disrupts the sphincter complex or its pudendal nerve supply, often presenting decades later as pelvic floor and sphincter function decline. In men and in many women the dominant cause is iatrogenic — sphincter division during fistula surgery being the classic — alongside neurological disease, diabetic autonomic neuropathy, spinal injury, rectal prolapse and faecal impaction with overflow in the elderly. Evaluation pairs endoanal ultrasound (mapping sphincter defects) with anorectal manometry and pudendal nerve studies; treatment ascends from conservative measures — fibre, loperamide, scheduled evacuation and biofeedback — through anterior sphincteroplasty for isolated traumatic defects, to sacral nerve stimulation, graciloplasty and, as a final resort, a stoma.
What you must remember
- Pattern decoding: urge incontinence = external sphincter/pudendal weakness; passive soiling = internal sphincter defect or impaired sensation; soiling with constipation = overflow until excluded.
- Obstetric injury mechanics: third-degree tears involve the anal sphincter (3a under half of external sphincter thickness, 3b more than half, 3c involving both external and internal sphincters), fourth-degree adding anorectal mucosa; recognised primary repair in theatre with antibiotics and laxatives prevents much late incontinence.
- Iatrogenic causes: fistula-in-ano surgery crossing too much external sphincter, haemorrhoidectomy dividing the anoderm and internal sphincter, dilatation procedures in the Indian setting, and difficult pelvic surgery.
- Neurological and systemic: diabetes with autonomic neuropathy, spinal cord injury and spina bifida, multiple sclerosis, dementia and stroke; chronic diarrhoea of any cause unmasks marginal sphincters.
- Assessment battery: endoanal ultrasound for sphincter defect mapping, anorectal manometry for pressures and squeeze, pudendal nerve terminal motor latency, defecography or MRI for prolapse and dyssynergia; colonoscopy when diarrhoea or impaction is unexplained.
- Conservative first line: loperamide to firm stool and raise squeeze pressure, fibre and stool regulation, scheduled toileting, perianal skin care, and biofeedback training — effective in a good proportion of all grades.
- Surgical ladder: anterior overlapping sphincteroplasty for a discrete traumatic defect; sacral nerve stimulation for refractory cases with intact or repaired sphincters; graciloplasty or an artificial bowel sphincter in selected centres; end stoma for intractable disease.
- Scoring habit: severity is graded with the Cleveland Clinic (Wexner) incontinence score from 0 to 20, tracking five symptoms across always-to-never scales — a research and clinic standard worth naming.
How to work through a case
A 58-year-old woman, para 4 with forceps deliveries decades ago, describes ten years of worsening urge incontinence, now avoiding social life; examination shows a patulous anus, decreased voluntary squeeze, and a scar from a poorly repaired tear. Endoanal ultrasound demonstrates an anterior defect of both sphincter ends with scarring, manometry shows low resting and squeeze pressures, and pudendal latency is normal — an anatomical, surgically correctable problem. She first optimises conservatively (loperamide, fibre, biofeedback), and when that plateaus, an anterior overlapping sphincteroplasty repairs the defect, with bowel-regulating therapy continued afterwards; results are good early, with some decline over years as childbirth-related tissue ages. Contrast a patient with passive soiling and normal sphincters on ultrasound but low resting pressure from internal sphincter weakness after haemorrhoid surgery: his pathway stays conservative and biofeedback-centred, since there is no discrete defect to repair. A third patient, elderly, constipated and "incontinent", is found to have a loaded rectum — disimpaction and a bowel programme cure the "incontinence", the cheapest diagnosis in the list.
How the exam frames it
Stems test the pattern-to-mechanism mapping (urge versus passive), the obstetric grading (third versus fourth degree, and the internal sphincter subdivision of 3c), and the investigation choice — endoanal ultrasound as the anatomical test, manometry as the functional one. The management ladder's ordering is frequently examined: biofeedback before surgery, sphincteroplasty for isolated defects, sacral nerve stimulation for refractory disease, and overflow always excluded first in the elderly.
Frequently asked questions
What distinguishes urge from passive faecal incontinence?
Urge incontinence means sensing the call but failing to hold it (external sphincter weakness); passive soiling occurs without awareness (internal sphincter dysfunction or impaired sensation).
Which investigation maps sphincter injury best?
Endoanal ultrasound, which images internal and external sphincter defects and their extent, paired with manometry for functional pressures.
When is anterior sphincteroplasty indicated?
For a discrete, symptomatic sphincter defect — typically obstetric or traumatic — with otherwise intact innervation, after conservative therapy has been optimised.
How does obstetric injury cause incontinence years later?
Direct sphincter disruption plus pudendal nerve stretch during delivery create a marginal continence reserve that decompensates with age, menopause and tissue degeneration.
What role does biofeedback play?
It is first-line therapy at almost every stage — training squeeze strength, coordination and rectal sensitivity — and improves a meaningful proportion of patients without surgery.