Urogenital ImagingFournier's gangrene
(Jean Alfred Fournier, 1832 - 1914, French dermatologist), a polymicrobial necrotizing fasciitis of the perineal, perirectal or genital area. It was first described in 1883 as an idiopathic condition of the scrotum. The disease now differs from the original description in that it includes females and is now realized to be secondary to a defined source of infection in 95% of the cases. The portal of entry may be urethral, rectal or cutaneous. The disease is rapidly progressive with a reported mortality rate of 10 - 30%. Successful treatment depends on early diagnosis, aggressive radical debridement of all areas of subcutaneous necrosis, and prompt institution of broad-spectrum intravenous antibiotics. Comorbid conditions are common, including diabetes mellitus, alcoholism, advanced age, malignancy and prolonged hospitalization.
The typical patient presents approximately 2-7 days after the onset of fever, appearing toxic and irritable, with gangrenous genitalia and leukocytosis. Most patients with this syndrome are between the ages of 50 and 70 years. Crepitus of the soft tissues is the physical hallmark of necrotizing fasciitis but is present in only 19 - 64% of patients at the time of diagnosis.
Current imaging techniques for the initial evaluation of Fournier's gangrene include radiography, sonography and CT. Diagnostic imaging may be useful to confirm the diagnosis, evaluate the extent of disease, detect the underlying cause, and follow the response to therapy.
Radiographs can show the presence of soft tissue gas in patients suspected of having necrotizing fasciitis. Abdominal radiographs (Fig.1) may reveal soft tissue gas before it becomes clinically evident and may also be useful to evaluate coexistent intra-abdominal disorders. Marked swelling of the scrotal tissues and air density within the interstices of the scrotum are characteristic. Subcutaneous emphysema may be seen to extend from the scrotum or perineum to the inguinal regions, the anterior abdominal wall and, occasionally, the thighs. The absence of subcutaneous air does not exclude the diagnosis of Fournier's gangrene.
In Fournier's gangrene, sonographic evaluation of the scrotum, scrotal contents, and surrounding structures shows a thickened and oedematous scrotal wall, gas within the scrotal wall, and unilateral or bilateral peritesticular fluid. Subcutaneous gas within the scrotal wall is the sonographic hallmark. The testes and epididymies are of normal size and architecture. Soft tissue air may also be noted to extend to the perineum and perirectal regions. This air often appears as numerous discrete, hyperechoic foci with posterior acoustic shadowing. Sonography (Fig.2) provides more information than does conventional radiography. The location of subcutaneous gas is more obvious. Scrotal sonography also reveals gas in the subcutaneous soft tissues before physical examination does.
The use of CT in establishing and determining the extent of Fournier's gangrene has not been extensively described. The characteristic CT appearance is of soft tissue thickening, stranding of fat surrounding the involved structures, and soft tissue gas dissecting along fascial planes. CT provides excellent depiction of both the presence and the extent of abnormal gas. Diagnosis is based on inflammatory and necrotic changes of perineal structures, including the superficial and deep fascial planes, and visualization of soft tissue gas within the subcutaneous tissues. Extensive soft tissue gas may surround the testicles and extend from the scrotum into the perineum. CT evaluation of the perineum and pelvis can often show the underlying cause of Fournier's gangrene such as perianal abscesses, fistulous tracts, incarcerated inguinal hernias, and sources of infection that are an intra-abdominal or retroperitoneal process. CT can also determine the extent of disease, allowing adequate surgical incisions to encompass the full extent of necrosis.
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