What labs should be obtained to diagnose Fournier's gangrene in a middle-aged to elderly male patient with risk factors such as diabetes, obesity, or immunocompromised states?

Laboratory Evaluation for Fournier's Gangrene

For every patient with suspected Fournier's gangrene, obtain a complete blood count, serum sodium, potassium, glucose, creatinine, magnesium, urea, inflammatory markers (C-reactive protein and procalcitonin), coagulation studies, and lactate level. 1, 2

Core Laboratory Panel

The WSES-AAST guidelines provide explicit recommendations for the initial diagnostic workup 1:

• Complete blood count (CBC) - essential for evaluating white blood cell count and hematocrit 1
• Electrolytes: serum sodium, potassium, and magnesium 1
• Renal function: serum creatinine and urea 1
• Glucose - particularly important given diabetes is the most significant risk factor 1
• Inflammatory markers: C-reactive protein and procalcitonin 1, 2
• Coagulation assessment - coagulopathy is a suggestive finding 1, 2
• Lactate - elevated levels indicate tissue hypoperfusion and correlate with severity 1, 2

Risk Stratification Scoring Systems

LRINEC Score for Early Diagnosis

The LRINEC score aids in early diagnosis of necrotizing infections and should be calculated using the laboratory values obtained. 1, 2

Fournier's Gangrene Severity Index (FGSI)

The FGSI incorporates nine clinical and laboratory parameters to predict mortality 1:

• Temperature, heart rate, respiratory rate
• Serum sodium, potassium, creatinine
• Hematocrit, white blood count, serum bicarbonate
• FGSI >9 indicates 75% probability of death 1
• Sensitivity: 65-88%, Specificity: 70-100% 1

Simplified FGSI (SFGSI)

The simplified FGSI focuses on only three parameters that showed significant differences between survivors and non-survivors: serum creatinine, hematocrit, and serum potassium. 1

• Provides 87% sensitivity and 77% specificity for predicting mortality 1
• Has been validated in multiple studies with good reliability 1

Critical Caveats

Do Not Delay Surgery for Laboratory Results

Never delay surgical intervention while waiting for laboratory results when clinical suspicion is high—Fournier's gangrene is a clinical diagnosis requiring emergency surgical debridement. 1, 2

• The presence of systemic toxicity, tissue necrosis, crepitation, and disproportionate pain mandates immediate surgery 2
• Laboratory tests support diagnosis and risk stratification but should not postpone definitive treatment 1

Blood and Tissue Cultures

Obtain blood cultures and cultures of any abscess material or debrided tissue to guide antibiotic therapy. 1

• Fournier's gangrene is typically polymicrobial with mixed aerobic and anaerobic flora 1
• Blood cultures are positive in 5-30% of cases 1

Practical Algorithm

High clinical suspicion (scrotal/perineal pain + systemic toxicity + necrosis/crepitation) → Draw labs stat + immediate surgical consultation → Proceed to emergency surgery without waiting for results 2

Moderate suspicion with equivocal findings → Draw complete laboratory panel → Calculate LRINEC score → Consider imaging if hemodynamically stable → Surgical consultation based on results 1, 2

The mortality rate of Fournier's gangrene is 20-50%, and time to surgery is the most critical determinant of outcome—laboratory evaluation should enhance but never delay clinical decision-making. 2, 3