How to diagnose urine leakage through a wound?

Diagnosing Urine Leakage Through a Wound

To identify if liquid coming through a wound is urine, perform chemical testing for creatinine and urea in the fluid, which will confirm urinary origin if positive. 1

Diagnostic Approach

Initial Assessment

• Visual inspection: Urine leakage may appear as clear to amber-colored fluid
• Odor: May have characteristic ammonia smell, especially if infection is present
• Timing: Increased drainage after urination suggests urinary origin

Confirmatory Testing

1. Chemical analysis of fluid:

   • Test for creatinine in the fluid (most specific)
   • Test for urea nitrogen in the fluid
   • Compare levels to serum values (fluid creatinine higher than serum confirms urinary origin)

2. Imaging studies (for source identification):

   • CT scan with IV contrast and delayed excretory phase: Gold standard for identifying the source of urinary leakage 1
   • Retrograde cystography: Critical if bladder injury is suspected 1
   • Retrograde urethrography: If urethral injury is suspected 1

Diagnostic Algorithm Based on Wound Location

Abdominal/Flank Wound

1. CT with IV contrast and delayed phase (urogram) to evaluate:

   • Kidney injury with extravasation
   • Ureteral injury
   • Bladder rupture (intraperitoneal vs. extraperitoneal)

2. Look for associated findings:

   • Hematuria (present in 77-100% of bladder injuries) 1
   • Increasing abdominal complaints and ascites (intraperitoneal leakage) 2
   • Regional edema without significant abdominal complaints (extraperitoneal leakage) 2

Pelvic/Perineal Wound

1. Retrograde cystography (conventional or CT) to determine:

   • Presence of bladder injury
   • Whether rupture is intraperitoneal or extraperitoneal 1

2. Retrograde urethrography for suspected urethral injury, especially with:

   • Blood at urethral meatus
   • Inability to urinate
   • Perineal/genital ecchymosis
   • High-riding prostate on exam 1

Clinical Clues by Urinary Tract Segment

Renal/Ureteral Origin

• Flank pain or tenderness
• Microscopic or gross hematuria
• Fever if infection present
• Oliguria due to internal reabsorption of urine 2
• Important laboratory clues: Discrepancy between serum and urine concentrations of urea, creatinine, and sodium 2

Bladder Origin

• Associated with pelvic fractures (in 60-90% of cases) 1
• Gross hematuria (common finding)
• Suprapubic pain or tenderness
• Inability to void or inadequate voiding

Urethral Origin

• Blood at urethral meatus (37-93% of cases) 1
• Perineal/genital ecchymosis
• Inability to urinate
• High-riding prostate on physical exam (in males)

Common Pitfalls and Caveats

• Don't rely solely on appearance: Clear fluid from a wound is not always urine; chemical testing is essential
• Don't miss associated injuries: Urinary tract injuries often occur with other trauma (e.g., pelvic fractures with bladder injuries)
• Don't overlook infection risk: Infected urine significantly increases wound infection risk (23.5% vs 8.7% with sterile urine) 3
• Don't delay diagnosis: Prolonged contact between urine and wound edges delays healing 4
• Don't forget post-surgical causes: Stone migration can cause obstruction and subsequent urine leakage after procedures like partial nephrectomy 5

Prompt diagnosis and management of urinary leakage are essential to prevent complications such as abscess formation, urinoma development, and wound healing problems.