Fournier gangrene

Fournier gangrene is necrotising fasciitis of the perineum. It is a true urological emergency due to the high mortality rate but fortunately, the condition is rare. It is primarily a clinical diagnosis and definitive treatment, typically consisting of surgical debridement and antibiotics. Imaging can aid in defining the extent of disease but must not delay treatment ⁹.

Epidemiology

Fournier gangrene is typically seen in men with diabetes mellitus, aged 50-70 years. Although historically women were rarely affected, the incidence appears to be increasing and is particularly associated withe morbid obesity ¹².Other predisposing factors include ⁹:

• end-stage renal and/or liver failure

• hypertension

• immunosuppression

• obesity (BMI >30)

• alcoholism

• smoking

• debility

• HIV

• diabetes

Clinical presentation

• perineal/scrotal pain, swelling, redness

• crepitus from soft tissue gas (up to 65%)

• systemically unwell

• fever and leucocytosis

Pathology

The source of infection can usually be identified, most commonly anorectal (such as from a perianal fistula or abscess) and less commonly genitourinary or perineal trauma. Sometimes the cause is not found.

The infection is usually polymicrobial. The most common organisms cultured are E.coli, Klebsiella, Proteus, Staphylococcus, and Streptococcus.

It begins as cellulitis that causes an endarteritis with thrombosis followed by a necrotising infection that spreads through the fascial planes. Initially, this is in the perianal and perineal regions, with later extension to the thighs and anterior abdominal wall. Importantly the testes are usually spared due to their different arterial supply from the aorta.

The organisms often produce gas, thus causing subcutaneous emphysema.

Radiographic features

The diagnosis is usually clinical. The role of imaging, most commonly employing CT, includes:

• diagnosis not established

• determine the extent of disease

• detect the underlying cause

Plain radiograph

Radiolucent soft-tissue gas may be seen in the region overlying the scrotum or perineum. Subcutaneous emphysema may extend from the scrotum and perineum to the inguinal regions, anterior abdominal wall, and thighs.

Ultrasound

• thickened scrotal wall

  • often oedematous, with linear hypoechoic fluid streaks interspersed ⁸

• echogenic gas foci in the scrotum are pathognomonic 

  • punctate, hyperechoic inclusions with posterior acoustic shadowing and reverberation artifacts

  • lacking clear margins, the acoustic shadowing from gas is often described as "dirty" 

• testes and epididymides spared (due to their separate blood supply)

• peritesticular fluid ⁷

  • anechoic fluid collections common, represent reactive hydroceles

CT

• soft tissue stranding, fascial thickening

• soft tissue gas locules

• extent of disease may be assessed prior to surgery

• cause of infection may be apparent (e.g. perianal abscess, fistula)

Administration of intravenous contrast can be helpful in defining abscesses and involvement of bowel ¹².

Radiology Reportreport

Regardless of modality, reports should aim to describe the extent of involvement (both air and soft tissue stranding) particularly in relation to involved fascial planes ¹². Ideally, the description should reference relevant facias:

• subcutaneous fat (Camper's fascia)

• superficial (Scarpa's) fascia

• Buck fascia

• Dartos fascia

• Colles fascia

• deep perineal fascia

Critical findings to assess and report is extension of disease into deeper tissues such as intraperitoneal involvement or extension into space of Retzius, as these will alter therapy and require a laparotomy ¹².

Any potential source of infection, such as perforated colorectal cancer needs to be sought and the presence or absence reported.

Given the time-critical nature of this disease, contacting the treating clinician immediately is of paramount importance.

Treatment and prognosis 

It is considered a urological emergency with a poor prognosis due to its high mortality rate (ranging ~15-50% ³). Imaging should be used judiciously, and must not allow the delay of potentially life-saving definitive treatment ⁹.

Management options include:

• immediate radical surgical debridement of necrotic tissue

• intravenous broad-spectrum antibiotics

• hyperbaric oxygen therapy

• testes replaced into the remaining scrotum or covered by skin graft (once infection settled)

History and etymology

It was first described by a French professor of dermatology at the University of Paris, and director of the renowned venereal Hospital of St Louis, Jean Alfred Fournier (1832-1914) ⁶ in 1883. He noted a fulminating gangrenous infection of male genitalia in young healthy males without an obvious cause.

Differential diagnosis

The differential in the setting of acute scrotal pain includes:

• epididymo-orchitis

• testicular torsion

• testicular trauma

• scrotal cellulitis/abscess