What is the outcome of an accidental injury to the external sphincter (muscle surrounding the urethra) during a digital visual internal urethrotomy (DVIU) for urethral stricture?

Accidental External Sphincter Injury During DVIU: Outcome

Accidental injury to the external urethral sphincter during direct visual internal urethrotomy results in urinary incontinence, which is a devastating complication that significantly impairs quality of life and is generally considered irreversible without complex reconstructive surgery.

Mechanism and Risk of Sphincter Injury

The external urethral sphincter is located at the membranous urethra (bulbomembranous junction) and is the primary mechanism for voluntary urinary continence. During DVIU for urethral stricture:

• The sphincter is at highest risk when strictures involve or are adjacent to the membranous urethra, particularly in posterior urethral strictures or proximal bulbar strictures 1

• Incision at the 12 o'clock position (dorsal) is safest to avoid injury to the sphincter mechanism, which is concentrated ventrolaterally 1

• Deep or circumferential incisions increase the risk of extending beyond the urethral mucosa into the sphincter muscle 1

Clinical Outcomes of Sphincter Injury

Urinary Incontinence

• Incontinence from sphincter injury during urethral procedures is uncommon but catastrophic when it occurs, with rates reported at <5% in most series but approaching 10-15% when strictures involve the membranous urethra 1

• The incontinence is typically stress incontinence (leakage with coughing, straining, physical activity) due to loss of the voluntary sphincter mechanism 1

• Recovery is unlikely without surgical intervention, as the sphincter muscle does not regenerate once transected 1

Other Potential Complications

• Erectile dysfunction can occur in 2.2-10.6% of cases following DVIU, caused by injury to cavernous nerves, late fibrosis after extravasation, or arteriovenous shunting between corpora cavernosa and corpus spongiosum 2

• Risk factors for erectile dysfunction include: external sphincterotomy at 3- and 9-o'clock positions, urethrotomy after trauma, long and dense strictures, and dilation over 22 Fr 2

Prevention Strategies

Technical Considerations

• Avoid DVIU for strictures at or near the membranous urethra; these should be referred for open urethroplasty by experienced reconstructive surgeons 1

• Limit incision depth to the stricture scar only, avoiding full-thickness cuts through the urethral wall 1

• Make incisions at the 12 o'clock position exclusively when treating bulbar strictures to stay away from the sphincter mechanism 1

• Avoid prolonged or heroic attempts at endoscopic procedures, as these increase injury severity and long-term sequelae without improving outcomes 1

Patient Selection

• DVIU should be avoided in patients with pelvic fracture-associated urethral injuries, as these frequently involve the membranous urethra and sphincter mechanism 1

• Patients with strictures >2 cm should be offered urethroplasty as initial treatment rather than DVIU, as success rates are very low and repeated procedures increase complication risk 1

• Recurrent strictures after failed DVIU should proceed to urethroplasty, as failure rates exceed 80% with repeat endoscopic procedures and complications accumulate 1, 3

Management of Established Sphincter Injury

• Immediate recognition and documentation of sphincter injury during the procedure is critical for counseling and planning 1

• Urinary catheter drainage for 2-3 weeks may allow some tissue healing, though functional recovery of the sphincter is unlikely 1

• Definitive treatment requires artificial urinary sphincter placement or male sling procedures, which should be performed by experienced reconstructive urologists 1

• Patients should be monitored for complications (stricture, erectile dysfunction, incontinence) for at least one year following any urethral injury or intervention 1

Critical Pitfalls to Avoid

• Never perform DVIU on membranous urethral strictures—these require open reconstruction 1

• Do not make deep circumferential incisions—limit depth to the stricture scar only 1

• Avoid lateral incisions (3 and 9 o'clock positions) in the bulbar urethra, as these risk neurovascular injury 2

• Do not persist with repeated endoscopic attempts when initial DVIU fails, as this increases stricture length and complication rates 1, 3