Posterior Urethral Injury

Posterior urethral injury is damage to the prostatic or membranous urethra, including the bladder neck. Most cases follow pelvic fracture.

The rest are iatrogenic (radical prostatectomy, transurethral prostate surgery, traumatic catheterisation, brachytherapy or ablative treatment) or penetrating (gunshot, impalement). Injury in women is rare and is usually obstetric or associated with pelvic fracture and vaginal laceration.

Pathophysiology. Fracture displacement tears the urethra at the fixed urogenital diaphragm. Surgical and thermal injury cause ischaemia of the urethra and anastomosis.

Extravasated urine collects in the pelvic and retropubic spaces, and complete disruption heals by fibrosis, forming a distraction defect or obliteration. Severity ranges from stretch and partial tear to complete disruption with a gap.

Blood at the meatus, inability to void, suprapubic fullness, perineal haematoma, and a high riding prostate in pelvic fracture. Iatrogenic injury is recognised at the time as a misplaced catheter, loss of resistance, contrast or irrigation extravasation, or visible perforation at endoscopy.

Later, leakage after surgery, retention, stricture and sepsis occur. Associated injuries include pelvic haemorrhage, bladder rupture and rectal injury.

• Retrograde urethrography with 20 to 30 mL of water soluble contrast before any catheter is passed in trauma.
• CT cystography (300 to 350 mL of dilute contrast with post-drain images) for bladder involvement. CT or MRI of the pelvis for associated injury and haematoma.
• Rectal examination, and proctoscopy if rectal injury is suspected.
• Combined antegrade and retrograde urethrography at 3 months defines the gap before repair.
• Urine culture, creatinine, haemoglobin.

Differential diagnosis.

• Anterior urethral injury
• Bladder rupture
• Bladder neck contracture
• Urethral false passage
• Rectal injury
• Anastomotic leak after prostatectomy
• Pre-existing stricture

• Resuscitation and control of bleeding come first in trauma.
• Drainage: suprapubic catheter of 12 to 16 Fr. Avoid blind urethral catheterisation.
• Pelvic fracture injury: suprapubic diversion with delayed perineal anastomotic urethroplasty at 3 months or more, success about 90 to 95%. Primary endoscopic realignment within 1 to 2 weeks in stable patients is an alternative, with a 16 Fr silicone catheter for 4 to 6 weeks and a high rate of later stricture.
• Bladder neck injury, intraperitoneal bladder rupture and rectal injury: immediate repair at laparotomy, with faecal diversion for rectal injury.
• Injury recognised at surgery (catheter or endoscope perforation, anastomotic defect): immediate repair of the urethra over a catheter for 14 to 21 days. Small endoscopic perforations with minimal extravasation need catheter drainage for 5 to 7 days and an antibiotic directed by culture.
• Penetrating injury: debridement, repair of associated bladder and rectal injury, and diversion.
• Women: early primary repair of urethral tears with vaginal laceration, within days.
• Antibiotics: ceftriaxone 2 g intravenously once daily, with metronidazole 500 mg intravenously every 8 hours when there is rectal injury, stopped within 24 to 72 hours once contamination is excluded.
• Complications: stricture, incontinence, erectile dysfunction (about 20 to 60% after pelvic fracture), fistula and infection.

Monitoring. Pericatheter urethrogram before catheter removal, uroflowmetry at 3, 6 and 12 months, and assessment of continence and erectile function.

Referral and escalation. Refer early to a reconstructive urologist. Urgent escalation for associated bladder neck, bladder or rectal injury, pelvic sepsis or instability.