Approach Considerations
Diagnosis of Fournier gangrene is based primarily on clinical findings, and treatment is based on those findings. Incisional biopsy may ultimately confirm the diagnosis.
The following studies are indicated:
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Complete blood cell count (CBC)
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Arterial blood gas (ABG) sampling
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Blood and urine cultures
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Disseminated intravascular coagulation (DIC) panel
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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. With either technique, the presence of subcutaneous air is very suggestive of the diagnosis in a patient with 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.
Chemistry Panel and Blood Gases
Perform a chemistry panel to evaluate for 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.
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.
Plain Radiography
Radiography should be considered to evaluate for the presence and extent of Fournier gangrene, especially when the clinical examination findings are inconclusive. [61, 62] 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, which manifest as areas of hyperlucency, may be evident on radiography before they become clinically apparent. However, the absence of air on plain films does not exclude the diagnosis.
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. [63, 64]
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.
Ultrasonography
Ultrasonography can be used to detect fluid or gas within the soft tissues. [65] 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. The testes and epididymides are usually normal.
Ultrasonography may reveal other causes of acute scrotal pain, including the following:
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Intratesticular injury
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Scrotal cellulitis
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Epididymo-orchitis
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Testicular torsion
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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.
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.
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.
Histologic Findings
Pathologic evaluation of the involved tissue may reveal the following pathognomonic findings of Fournier gangrene:
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Necrosis of the superficial and deep fascial planes
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Fibrinoid thrombosis of the nutrient arterioles
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Polymorphonuclear cell infiltration
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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 course of the disease.
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Necrotizing infection results when the pathogen is extremely virulent or, most commonly, when a combination of microorganisms act synergistically in a susceptible immunocompromised host.
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Photomicrograph of Fournier gangrene (necrotizing fasciitis), oil immersion at 1000X magnification. Note the acute inflammatory cells in the necrotic tissue. Bacteria are located in the haziness of their cytoplasm. Courtesy of Billie Fife, MD, and Thomas A. Santora, MD.
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Photograph of a morbidly obese male with long-standing phimosis. This condition led to urinary incontinence, perineal diaper rash–like dermatitis, and urinary tract infection. Ultimately, he presented with exquisite perineal pain. An examination with the patient under anesthesia was necessary to discover the necrotizing infection that appeared to originate in the right bulbourethral gland. Courtesy of Thomas A. Santora, MD.
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Patient with Fournier gangrene following radical debridement. A dorsal slit was made in the prepuce to expose the glans penis. Urethral catheterization was performed. Incision into the point of maximal tenderness on the right side of the perineum revealed gangrenous necrosis that involved the anterior and posterior aspects of the perineum, the entirety of the right hemiscrotum, and the posterior medial aspect of the right thigh. The skin and involved fascia were excised from these areas. Reconstruction of this defect was performed in a staged approach. A gracilis rotational muscle flap taken from the right thigh was used to fill the cavity in the posterior right perineum as the first step. The remainder of the defect was covered with split-thickness skin grafts. This patient made a full recovery.
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Fascial envelopment of the perineum (male). Note how Colles fascia completely envelops the scrotum and penis. Colles fascia is in continuity cephalad to the level of the clavicles. In the inguinal region, this fascial layer is known as Scarpa fascia. Familiarity with this fascial anatomy, along with recognition that necrotizing fasciitis tends to spread along fascial planes, makes it easy to understand how a process that starts in the perineum can spread to the abdominal wall, the flank, and even the chest wall.
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Examination of an anesthetized man with alcoholism and known cirrhosis who presented with exquisite pain limited to the scrotum. Note the erythema of the scrotum and the look of skepticism on the face of one of the surgeons. Courtesy of Thomas A. Santora, MD.
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In a man with alcoholism and known cirrhosis who presented with exquisite pain limited to the scrotum, opening of the scrotum along the median raphe liberated foul-smelling brown purulence and exposed necrotic tissue throughout the mid scrotum. The testicles were not involved. Courtesy of Thomas A. Santora, MD.
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The same patient depicted in Images 6 and 7. Following resolution of the infection, the wound was covered with a split-thickness skin graft. The option of delayed primary closure of this wound was not chosen in this patient because of concern for tension on the closure. Courtesy of Thomas A. Santora, MD.
