Can the deep (divided) portion of the external anal sphincter be strengthened?

Can the Deep (Divided) External Anal Sphincter Be Strengthened?

Yes, the divided external anal sphincter (EAS) can be strengthened through structured pelvic floor biofeedback therapy, which should be implemented for at least 3 months before considering any surgical intervention. 1

Evidence for Non-Surgical Strengthening

Pelvic Floor Biofeedback Therapy

• Structured pelvic floor biofeedback therapy using electronic and mechanical devices can improve EAS strength, sensation, and coordination in patients with sphincter dysfunction 1, 2
• The American College of Gastroenterology recommends a minimum of 3 months of documented pelvic floor therapy before declaring conservative treatment failure 1
• Approximately 70-80% of patients with functional pelvic floor disorders respond to properly administered biofeedback therapy when the underlying problem involves muscle weakness or dyscoordination rather than complete structural disruption 2

Resistance Exercise for Sphincter Strengthening

• Repetitive contractions against a compressible resistive load induce muscle fatigue more effectively than contractions without resistance, which is essential for successful muscle strengthening 3
• Exercise against resistance shows significant decrease in anal contractile integral during repetitive contractions, demonstrating true muscle fatigue—a prerequisite for strengthening 3
• Both short repetitive squeeze contractions (40 repetitions of 3 seconds) and long squeeze contractions (30 seconds) against resistance are more effective at inducing fatigue than unresisted exercises 3

Surgical Repair Considerations

When Surgical Repair Is Indicated

• If a sphincter defect has been identified by digital rectal examination and endosonography, surgical sphincteroplasty can be performed using either overlapping or end-to-end technique with similar outcomes 4
• The American Journal of Obstetrics and Gynecology recommends identifying and reapproximating both the internal and external anal sphincter during obstetric anal sphincter injury repair 5

Surgical Technique for EAS Repair

• The EAS should be repaired using either end-to-end or overlapping technique with 3-0 delayed absorbable suture 5
• A 2013 Cochrane meta-analysis found no significant difference in pain, dyspareunia, or flatal incontinence between end-to-end and overlapping techniques, though overlapping repair showed lower fecal urgency and better anal incontinence scores at 1 year 5
• More than 60% of patients initially improve after sphincteroplasty, but benefit decreases to 40-50% after 5 years 4

Critical Limitation of Surgical Repair

• Sphincteroplasty success rates decline significantly over time, with only 28% remaining continent at 40 months and a predicted median time to relapse of 5 years 1
• This deterioration underscores why pelvic floor therapy should always be attempted first and continued post-operatively 1

Treatment Algorithm for Divided EAS

Initial Management (First 3-6 Months)

1. Begin structured pelvic floor biofeedback therapy immediately using electronic and mechanical devices to improve strength, sensation, and coordination 1, 2
2. Incorporate resistance-based exercises using an intra-anal compressible device to maximize muscle fatigue and strengthening 3
3. Document baseline sphincter function with anorectal manometry to identify pre-existing defects and guide treatment selection 1

Escalation if Conservative Therapy Fails

• If no improvement occurs after 3 months of consistent therapy, escalate to formal biofeedback with specialized therapists 1
• If biofeedback fails after 6 months total, progression should be: perianal bulking agents → sacral nerve stimulation → sphincteroplasty 1

Sacral Nerve Stimulation as Alternative

• Sacral nerve stimulation (SNS) should be considered for moderate or severe fecal incontinence after failed conservative measures, with 89% therapeutic success at 5 years 1
• A morphologically intact anal sphincter is not a prerequisite for SNS success—defects up to 33% of the circumference can be effectively treated 6
• SNS can increase squeeze pressure significantly in patients with sphincter defects, even without surgical repair 6

Critical Pitfalls to Avoid

• Do not proceed directly to sphincteroplasty without at least 3 months of documented pelvic floor therapy in patients with baseline sphincter dysfunction 1
• Many patients labeled as "refractory" have not received optimal conservative therapy, which must include structured biofeedback with adequate duration 5
• Post-operative pelvic floor rehabilitation is essential to improve and maintain sphincteroplasty outcomes 7
• Prognosis worsens with increasing age and supplementary descending pelvic floor, so earlier intervention with conservative therapy is preferable 4

Prognostic Indicators for Success

Favorable Factors

• Patients who demonstrate any improvement within the first 4-6 weeks of pelvic floor therapy are highly likely to achieve substantial benefit with continued treatment 2
• Younger patients without significant comorbidities (diabetes, neurological disorders, inflammatory bowel disease) have better outcomes than those with systemic conditions affecting nerve function 2
• Males have better sphincteroplasty outcomes than multiparous women, whose sphincters are often denervated 7

Unfavorable Factors

• Abnormal pudendal nerve terminal motor latency (>2.2 milliseconds) indicates denervation and predicts poorer outcomes with both conservative and surgical therapy 8
• Presence of megarectum or severe rectal hyposensitivity suggests neurogenic dysfunction less amenable to sphincter strengthening alone 8