Urethrocutaneous Fistula

Urethrocutaneous fistula is an abnormal tract between the urethra and the skin of the penis, scrotum or perineum. It is the most common complication of hypospadias repair, with reported rates of roughly 5 to 15% and a wider range of 4 to 20%, depending on severity of hypospadias and technique.

It also follows urethroplasty, trauma, catheter pressure necrosis, periurethral abscess and Fournier gangrene, tuberculosis and schistosomiasis.

Pathophysiology. Poor blood supply to the urethral repair, infection, tension, overlapping suture lines or distal obstruction (meatal stenosis, stricture) causes a breakdown in the closure, and urine passes through the defect, which then epithelialises and persists.

A stream from a pinhole, or leakage of urine from the shaft, scrotum or perineum during voiding, often with a weak stream at the meatus. The opening may be single or multiple, and the surrounding skin may be inflamed or macerated. Check for distal stenosis, scarring, balanitis xerotica obliterans, and any abscess or cellulitis.

• Clinical examination, observing voiding.
• Methylene blue or saline injected through the meatus or into the fistula.
• Retrograde urethrography with voiding cystourethrography for tract and distal stricture or diverticulum.
• Urethroscopy, uroflowmetry for obstruction, and urine culture.
• Biopsy if the edge looks suspicious or in long standing disease.

Differential diagnosis.

• Periurethral abscess with a sinus
• Urethral diverticulum with a skin opening
• Meatal stenosis or distal stricture with proximal leak
• Skin sinus from other cause
• Urethral cancer
• Tuberculous or schistosomal sinus

• Observe for at least 6 months after hypospadias surgery before repair, as small fistulae can close and tissue needs time to mature.
• Treat infection, and correct distal obstruction (meatotomy, stricture repair) before or at the time of the fistula repair, otherwise failure is likely.
• Repair: dissect the tract to the urethra, excise it, invert the urethral closure with fine absorbable sutures (6/0 or 7/0), add an interposed vascularised cover (dartos, tunica vaginalis), and close the skin with no overlapping suture lines. Larger or complex fistulae need flap or graft urethroplasty.
• Catheter or diversion for 3 to 7 days in simple repairs and 7 to 14 days in complex ones. Give a single dose of antibiotic cover directed by culture.
• Recurrence occurs in a meaningful minority and rises with larger, multiple and radiated or scarred fistulae.
• Necrotising infection (Fournier gangrene) needs emergency debridement and broad spectrum antibiotics, then later reconstruction.

Monitoring. Review at 2 weeks, 3 months and 12 months, with uroflowmetry and a check of the stream and skin.

Referral and escalation. Refer to urology, with paediatric or reconstructive urology for hypospadias complications. Urgent referral for abscess, cellulitis or necrotising infection.