Why does radical prostatectomy (prostate removal) cause urinary incontinence in males?

Why Prostate Removal Causes Urinary Incontinence

Radical prostatectomy causes urinary incontinence primarily through disruption of the urinary sphincter mechanism and damage to critical anatomical structures that maintain continence, including the external urethral sphincter, membranous urethra, neurovascular bundles, and supporting pelvic floor structures. 1, 2

Anatomical Mechanisms of Post-Prostatectomy Incontinence

The surgical removal of the prostate disrupts several key anatomical structures essential for urinary control:

Direct Sphincter Disruption

• The external urethral sphincter and membranous urethra are directly manipulated during surgery when the prostate is separated from the urethra and the bladder is reconnected to the urethral stump (vesicourethral anastomosis). 1
• Shorter membranous urethral length measured preoperatively on MRI is consistently associated with increased incontinence risk, as there is less functional sphincter tissue remaining after surgery. 3, 4
• The internal sphincter at the bladder neck is often removed or disrupted during prostate removal, eliminating one layer of continence control. 1

Supporting Structure Damage

• The levator ani muscle, puboprostatic ligaments, endopelvic fascia, and neurovascular bundles all contribute to continence, and surgical trauma to these structures impairs the coordinated function needed for urinary control. 1
• Damage to the neurovascular bundles (unless bilateral nerve-sparing is performed) can denervate the sphincter mechanism, reducing its contractile function. 3, 1

Anastomotic Complications

• Anastomotic stricture develops in 5-14% of men where the bladder is joined to the urethra, and surgical correction of these strictures can further compromise sphincter function and worsen incontinence. 3

Patient-Specific Risk Factors

Certain patient characteristics increase vulnerability to post-prostatectomy incontinence:

• Advanced age is consistently associated with increased incontinence risk, likely due to baseline sphincter weakness and reduced tissue healing capacity. 3, 4, 5
• Larger prostate size increases risk, possibly due to more extensive surgical dissection required. 3, 4
• Prior transurethral resection of the prostate (TURP) significantly increases incontinence risk, as the sphincter mechanism may already be compromised. 3, 5

Clinical Course and Expected Recovery

Understanding the natural history helps explain the mechanism:

• Most men are completely incontinent immediately after catheter removal, demonstrating that the sphincter mechanism requires time to recover from surgical trauma. 3
• Gradual improvement occurs over 3-12 months as inflammation resolves, tissues heal, and neuromuscular function recovers. 3, 4
• Long-term incontinence persists in 12-16% of patients at 12 months, indicating permanent structural or functional damage in this subset. 3, 4
• About 8-9% require subsequent surgical procedures (such as artificial urinary sphincter), confirming that the damage can be irreversible in some cases. 3, 4

Special Forms of Post-Prostatectomy Incontinence

Beyond typical stress incontinence, specific mechanisms cause unique patterns:

• Climacturia (orgasm-associated incontinence) occurs in up to 30% of men, likely due to disruption of the bladder neck and loss of the normal closure mechanism during ejaculation. 3, 4
• Shorter functional urethral and penile length after surgery are risk factors for climacturia, suggesting that anatomical shortening reduces the effective sphincter zone. 3

Surgical Technique Considerations

The evidence reveals important technical factors:

• Bilateral neurovascular bundle preservation is the only surgical maneuver with evidence for improving continence recovery, as it preserves innervation to the sphincter. 3
• Different surgical approaches (open, laparoscopic, robotic) do not significantly impact incontinence rates, indicating that the fundamental anatomical disruption is unavoidable regardless of technique. 3
• Attempts at bladder neck preservation, urethral length preservation, and musculofascial reconstruction are employed to reduce incontinence, though high-quality evidence for their effectiveness remains limited. 1

Common Pitfall

A critical caveat is that 4% of men who report complete continence preoperatively actually have measurable urine loss (≥8g on pad testing), meaning some baseline sphincter dysfunction may be unrecognized and will be unmasked or worsened by surgery. 5