Fournier Gangrene Workup

Updated: Nov 12, 2016
  • Author: Vernon M Pais, Jr, MD; Chief Editor: Bradley Fields Schwartz, DO, FACS  more...
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Workup

Approach Considerations

Diagnosis of Fournier gangrene is based primarily on clinical findings, and treatment is based on these clinical findings. Incisional biopsy may ultimately confirm the diagnosis.

The following studies are indicated:

  • Complete blood cell count (CBC)
  • Blood and urine cultures
  • Disseminated intravascular coagulation (DIC) panel
  • Cultures of any open wound or abscess

Pelvic imaging studies can be extremely valuable, although sensitivities and specificities of different radiologic modalities are not established. Plain radiography should be the initial imaging study, while computed tomography (CT) should be considered the imaging study of choice. In both cases, the presence of subcutaneous air are very suggestive of the diagnosis in the presence of an appropriate clinical history. In addition, any test deemed necessary to assess exacerbation of a comorbid condition (eg, electrocardiogram and cardiac enzyme evaluation in patients with coronary artery disease) is warranted.

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Chemistry Panel and Blood Gases

Perform a chemistry panel to evaluate possible electrolyte disturbances; to look for laboratory evidence of dehydration (elevated blood urea nitrogen [BUN]/creatinine ratio), which tends to occur as the disease progresses; and to evaluate for glucose intolerance, which may be due to preexisting diabetes or sepsis-induced metabolic disturbance.

Arterial blood gas (ABG) sampling provides a more accurate assessment of acid/base disturbance. Acidosis with hyperglycemia or hypoglycemia may be present.

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Blood Tests

Obtain a CBC to assess the immunologic stress induced by the infectious process, check the adequacy of the red blood cell mass, and evaluate the potential for sepsis-induced thrombocytopenia.

A coagulation profile (ie, prothrombin time, activated partial thromboplastin time, platelet count, fibrinogen level) is helpful to look for sepsis-induced coagulopathy.

Blood samples should be drawn for culture to assess for septicemia. Consider type and screen if surgical exploration is undertaken.

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Plain Radiography

Radiography should be considered to evaluate for the presence and extent of Fournier disease, especially when the clinical examination findings are inconclusive. [44, 45] Gas within the soft tissues is detected more commonly with imaging modalities than with the physical examination. (Note that in the setting of a clinical suspicion of Fournier gangrene, demonstration of soft-tissue gas or detection of subcutaneous crepitation is an absolute indication for surgical exploration.)

Plain radiography should be the initial imaging study. It may reveal moderate-to-large amounts of soft-tissue gas, foreign bodies, or scrotal tissue edema. Soft-tissue gas collections (manifest as areas of hyperlucency) may be evident on radiography before they become clinically apparent. However, absence of air on plain films does not exclude the diagnosis.

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Computed Tomography

CT scanning is readily available in most hospitals and should be considered the imaging study of choice, as it defines the extent of the disease more specifically than plain films or ultrasound. CT scanning can reveal smaller amounts of soft-tissue gas than plain radiography and can demonstrate fluid collections that track along the deep fascial planes. [46, 47]

Findings include soft-tissue and fascial thickening, fat stranding, and soft-tissue gas collections. CT scan often identifies the underlying cause of the infection (eg, perirectal abscess). The findings may assist in surgical planning.

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Ultrasonography

Ultrasonography can be used to detect fluid or gas within the soft tissues. [48] Gas in the scrotal wall is the "sonographic hallmark" of Fournier gangrene. Air may be appreciated in perineal and/or perirectal areas. Scrotal wall edema may be seen. Testes and epididymides are usually normal.

Ultrasonography may reveal other causes of acute scrotal pain, including intratesticular injury, scrotal cellulitis, epididymo-orchitis, testicular torsion, and inguinal hernia.

The drawback of ultrasonography is the need for direct pressure on the involved tissue; patients with Fournier gangrene probably will not be able to tolerate this procedure.

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Magnetic Resonance Imaging

Use of MRI in Fournier gangrene is not well described in the literature. MRI yields greater soft tissue detail than does CT scanning; however, MRI requires greater time, with limited ability for patient monitoring during testing. These logistical challenges, which are not shared by CT scanning, limit the practical usefulness of MRI, especially in patients with critical illness. Use of MRI should not delay operative intervention if the diagnosis is highly suspected.

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Biopsy

An incisional biopsy at the time of surgical debridement allows pathological distinction of Fournier gangrene (ie, necrotizing infection) from severe cellulitis. The former would benefit from excisional debridement, while the latter rarely requires surgical excision.

The biopsy sample should be taken from the point of maximal tenderness, and it should include skin and superficial and deep fascia. This sample may be sent for frozen-section analysis to assess for fascial necrosis. Early fascial involvement may appear as edematous fascia on gross inspection but may appear as frank necrosis on microscopic analysis.

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Histologic Findings

Pathologic evaluation of the involved tissue may reveal the following pathognomonic findings of Fournier gangrene:

  • Necrosis of the superficial and deep fascial planes
  • Fibrinoid thrombosis of the nutrient arterioles
  • Polymorphonuclear cell infiltration
  • Microorganisms identified within the involved tissues

Fibrinoid thrombosis of the nutrient vessels that supply the superficial and deep fascia is the finding that most commonly indicates Fournier disease. Widespread necrosis of the fascia with acute inflammatory cell infiltration and necrotic debris is frequently evident, as is the presence of causative microorganisms within the tissues.

This extensive inflammatory process is frequently present deep to intact skin. The skin itself is often minimally involved with the inflammatory process until late in the disease.

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