What is the workup to rule out Fournier's gangrene?

Workup to Rule Out Fournier's Gangrene

Diagnosis of Fournier's gangrene requires prompt clinical examination followed by appropriate imaging, with contrast-enhanced CT scan being the preferred modality due to its high sensitivity (90%) and specificity (93.3%) for evaluating disease extent and identifying underlying causes. 1

Clinical Examination

• Assess for cutaneous manifestations: erythema, subcutaneous crepitations, patches of gangrene, foul smell, purulence/wound discharge, and tenderness to palpation 1
• Look for potential portals of entry from anorectal, genitourinary, or local cutaneous sources 1
• Evaluate for systemic signs of infection including fever, tachycardia, hypotension, and altered mental status 2
• Check for risk factors: diabetes mellitus, alcoholism, immunosuppression, and advanced age 3

Laboratory Investigations

• Complete blood count with differential (looking for leukocytosis) 1
• Comprehensive metabolic panel including sodium, potassium, glucose, creatinine, and magnesium 1
• Inflammatory markers: C-reactive protein and procalcitonin 1
• Coagulation profile and serum lactate 1
• Blood cultures before initiating antibiotics 1

Imaging Studies

• Contrast-enhanced CT scan is the preferred imaging modality with:

  • Sensitivity approaching 90% for diagnosing necrotizing soft tissue infections 1
  • High specificity (93.3%) for evaluating disease extent 1
  • Ability to identify potential underlying causes 1

• Bedside ultrasound is an alternative when CT is not available or feasible:

  • Can be performed at the patient's bedside 1
  • Shows marked thickening of scrotal skin, soft tissue inflammation, collections/abscesses, and subcutaneous gas 1
  • Can demonstrate paratesticular fluid before clinical crepitus is evident 1
  • Does not require radiation or intravenous contrast 1

• Plain radiographs may demonstrate gas in soft tissue planes but are less sensitive 1

• MRI with gadolinium contrast has excellent soft tissue resolution but limited utility in emergency settings due to extended examination time and limited access 1

Important Considerations and Pitfalls

• Do not delay surgical intervention to obtain imaging in hemodynamically unstable patients or those with clear clinical signs of Fournier's gangrene 1

• The Fournier's Gangrene Severity Index (FGSI) should be calculated to predict outcomes:

  • Combines physiological parameters: temperature, heart rate, respiration rate, sodium, potassium, creatinine, leukocytes, hematocrit, and bicarbonate 1
  • FGSI score above 9 is sensitive and specific as a mortality predictor 1, 3

• Procalcitonin monitoring may be useful in the diagnostic workup and to guide antimicrobial therapy 1

• Cultures of infected fluid and tissues should be obtained during initial surgical debridement to guide specific antibiotic management 1

• Remember that testicular involvement is rare due to their non-perineal blood supply 1

• The mortality rate approaches 20-50% in many contemporary series, emphasizing the importance of early diagnosis 1, 3