Special investigations to be done include a full blood count, clotting profile, urea, creatinine and electro lytes, liver function tests, blood glucose, blood gases, group and screen, HIV and VDRL.
Abnormal findings include anemia, thrombocytopenia, coagulopathy, hyponatremia, and raised urea and creatinine. Hypocalcemia may occur in some cases, subsequent to the chelation of ionized calcium by triglycerides liberated by bacterial lipases.
Leukocytosis with a white cell count above 15,000 mm3 and a left shift is found in more than 90 % of cases. Neutrophilia indicates overwhelming bacterial infection. It is noteworthy that leukocytosis may not be present in immunosuppressed patients (Baskin et al. 1990; Laucks 1994). Anemia maybe present as part of the septic profile. Coagulopathy may be indicated by a raised prothrombin time (PT) and partial thromboplastin time (PTT), and thrombocytopenia. Raised fi-brinogen levels and positive D-dimers may herald the onset of disseminated intravascular coagulation (DIC).
Blood and urine cultures, together with wound swabs and tissue specimens for bacterial culture are very important. The HIV status should be determined in all patients, as Fournier's gangrene may be the presenting condition in patients with HIV.
Radiologic imaging maybe useful if the diagnosis is in doubt, but it should not delay the surgical management. An x-ray of the abdomen and pelvis may demonstrate gas in the subcutaneous fascial layers of the perineum and abdominal wall.
Ultrasound provides superior imaging of the perineum and scrotum. The appearance of hyperacoustic shadows in the fascial planes is diagnostic of gas formation, and it may be more sensitive than clinical evaluation for crepitus (Kane et al. 1996). However, in patients with extreme tenderness on palpation, ultrasound examination may be too painful.
Computerized tomography (CT) is more sensitive in demonstrating subcutaneous and retroperitoneal gas and fluid collections, but the use of contrast should be avoided in patients with renal failure. Magnetic resonance (MR) is the most sensitive imaging modality for evaluating pathology in soft tissues, but is expensive and not readily available.
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