Introduction

Based on his descriptions of the condition in five of his patients, Fournier gangrene was named after the French physician Jean Alfred Fournier in 1883. Fornier gangrene is necrotising fasciitis of the genital, scrotal, perineal, and perianal regions. Necrotising fasciitis is widely described in the press as a “flesh-eating disease” and is an infection that leads to clots forming in the small blood vessels of the skin and soft tissues, leading to cell death and gangrene. The infection spreads along the planes of fibrous tissue in the body that separate the soft tissues of the body into compartments. These planes are called fascia and have a relatively poor blood supply. The cycle of infection, inflammation, damage to the small arteries in the soft tissues, and gangrene leads to a rapidly progressive and destructive disease that eats away at the soft tissues and is frequently fatal.^1,2 

Fortunately, Fournier gangrene is rare, with an incidence of 1.6 cases per 100,000 in people assigned male at birth (AMAB). Whilst the disease can affect both sexes, people with AMAB are most frequently affected, with a ratio of 10:1. Most cases are found in people with AMAB aged over 50. A predisposition for the disease occurs in any cause of a weakened immune system however, diabetes, alcohol abuse and malignancy are the most common predisposing factors.³

Fournier gangrene is frequently fatal, with a mortality rate of around 40% however, if the diagnosis is delayed some studies reveal mortality rates as high as 88%. Fournier gangrene is considered a surgical emergency, early diagnosis and surgical debridement (cutting away) of affected tissue can reduce the mortality rate by as much as 50%. The impact of early intervention on improving death rates and the rapidly progressive nature of the infection, early diagnosis is crucial to saving lives and preventing severe tissue destruction.^3,4 

Pathophysiology of fournier gangrene

The infection in Fournier disease includes multiple species of bacteria. Whilst usually causing less severe infections on their own, the combination of these bacteria, both anaerobic and aerobic, leads to the cycle of inflammation, occlusive clots forming in the small arteries of the soft tissues and cell death (ischemia) from lack of blood supply that leads to gangrene. Dead gangrenous tissue releases toxic compounds and serves as a reservoir for further infection to develop and thus the infection, inflammation and gangrene spreads into surrounding healthy tissues. 

Within the body, the soft tissues are divided into compartments by tough, fibrous sheets of tissue called fascia. In necrotising fasciitis and Fournier gangrene, the infection spreads along these fascial planes and thus can spread into the deeper tissues around the genitals and perineum, without superficially visible skin changes being initially apparent. This can make the disease difficult to diagnose early on as there may be little to observe by externally examining the skin of the genitals and perineum even in the presence of deep infection.⁵

Initially, the infection usually begins from a genito-urinary, rectal or perianal infection (e.g. a peri-anal abscess) a superficial infection of the skin of the perineum or genitals, or localised trauma or surgery. Risk factors may be generalised:

• Diabetes
• Chronic alcoholism
• Liver and kidney disease
• Obesity
• Intravenous drug abuse
• HIV
• Chemotherapy
• Cancer
• Other immunocompromised states 

Some risk factors may be more specific and can include any situations likely to introduce infection into the genital and perineal tissues.

• Peri-anal abscess
• Urethral stricture
• Prostate cancer
• Surgery (prostate biopsy, cystoscopy)

Clinical presentation

Intense discomfort in the genital or perineal area can often present as the initial symptom, and frequently, this pain is disproportionately intense compared to the examination results, which may show little or no abnormalities in the early stages. Localised symptoms may include:

• Redness
• Tenderness to touch
• Swelling
• Itching of the skin overlying the scrotum or labia or the perineum

Generalised features of the infection may also be present and include:

• Fever
• Nausea
• Vomiting 
• Feeling generally unwell

As the condition progresses, the scrotum may swell and gas formation may be felt under the skin. This sign, called crepitus, is the creaking of the skin due to gas bubbles forming under the skin produced by gas-forming bacteria under the Clostridium species. At this stage, a high fever is usually present and discharge of pus may be seen from the affected skin.

Once there is a significant infection, features of gangrene may become apparent these include marked crepitation, purple discolouration of the skin, blisters or bullae forming over the affected skin and a putrid-smelling discharge of pus from the skin. Patchy black discolouration of the skin is highly indicative of gangrene and is a late feature.

During the late stages of presentation signs and symptoms, sepsis (septicaemia) may occur. This condition is characterised by a rapid thready pulse (tachycardia), low blood pressure, cold extremities, pallor, clammy skin, rapid breathing and a progression to failure of the vital organs (liver, kidney), which may affect the person’s consciousness level.⁷

Diagnostic approaches

Given the significance of prompt surgical intervention in enhancing survival rates, the clinical indicators mentioned earlier should serve as the main basis for diagnosis. While it is not ideal to postpone treatment awaiting additional test results, there are instances where cases might not show typical symptoms right away, or the comprehensive details of the disease might not be evident from a simple examination. Thus, blood tests and imaging can provide valuable support for the diagnosis.

A strong awareness should be maintained, especially in individuals with risk factors for Fournier gangrene, and it is essential to examine the genital and perineal areas in patients who may otherwise be overlooked. Including those who are bed-bound, have spinal injuries or quadriplegia, are severely obese, elderly and frail, or have dementia or issues with communication.

Blood tests

C-reactive protein (a marker of inflammation), a full blood count, lactate, blood gasses, tests of kidney and liver function, and glucose levels are all useful in evaluating Fournier gangrene. C-reactive protein will be raised, a full blood count may show a raised white cell count and a drop in haemoglobin. Kidney function tests may show raised creatinine and blood glucose levels may be raised. A scoring system based on these parameters in the blood has been developed to indicate the likelihood of necrotising fasciitis being present, known as the Laboratory Risk Indicator for Necrotising Infection (LRINEC). Higher scores help distinguish necrotising infection from other forms of soft tissue infection. It can be a useful piece of information in the evaluation of suspected Fournier gangrene.⁸

Blood cultures and wound cultures

All patients with suspected Fournier gangrene should be started on a cocktail of broad-spectrum intravenous antibiotics designed to cover the likely anaerobic and aerobic bacteria responsible for typical infections before the results of microbiological tests are available to avoid delays in treatment. However, culturing the patient’s blood and any exudate from the wound can help tailor the antibiotic regime to specific organisms which may be present once the results are available. This is also true of selecting antimicrobial agents in rarer organisms that may be implicated in Fournier gangrene, such as fungal organisms.⁸

Imaging techniques

X-ray

Plain X-rays can be used to detect gas forming within the soft tissues. If present, gas may be seen on the X-ray, in addition to swelling of the tissues around the scrotum. Gas may be visible before the clinical features of crepitus are present. However, the absence of gas beneath the skin on an X-ray does not necessarily rule out Fournier gangrene. Thus other techniques are more sensitive than X-rays.⁹

Ultrasound

Ultrasound scanning of the scrotum is generally more beneficial. It can reveal a thickened scrotal wall, so-called “dirty shadowing” caused by small pockets of gas that may be seen in the scrotal wall. Additionally, ultrasound can detect fluid accumulation within the scrotum. The presence of gas within the scrotum is considered indicative of Fournier gangrene. One of the advantages of ultrasound imaging is that it is quick, straightforward to conduct, and can be performed at the bedside of the patient.⁹

CT scan

CT Scanning is even more sensitive and specific compared to ultrasound in the detection of Fournier gangrene. Specific changes are noted on CT scanning including uneven thickening of the planes of fascia and collections of fluid and gas. CT is much better at showing the extent of the disease and is useful therefore in preparing for surgery. After surgical debridement, CT can be used as a useful tool to check healing or to identify new pockets of infection after surgery. It may also shed light on the source of the infection in Fournier gangrene as it will show up potential sources of infection such as anal fistulas.⁹

Whilst magnetic resonance imaging (MRI) is excellent for visualising soft tissue, it is less commonly used in the evaluation of Fournier’s gangrene largely because obtaining MRI images may represent an unacceptable delay in treatment and adequate imaging can usually be obtained from CT scanning, and also MRI scanning is costly.⁹

Fournier gangrene severity index

The Fournier’s gangrene severity index (FGSI) is a scoring system that combines readings of the patient’s vital signs with values from their laboratory blood tests. It aims to predict the severity and the likelihood of survival based on these parameters. Whilst some research supports the use of the FGSI, its predictive value is still controversial.⁷

Challenges in diagnosis

Diagnosis, particularly early on in Fournier gangrene can be challenging as there may be no localised symptoms. Early symptoms may present like fever, malaise, vomiting etc. Typically, a case takes 5 days from onset to present to the hospital. However, atypical cases may have a longer early or prodromal period without localised genital signs during which diagnosis is difficult. 

Furthermore, Fournier gangrene may be confused with other causes of redness and swelling in the genital or perineal area such as a localised abscess or cellulitis in which case the LRINEC score is useful in distinguishing Fournier gangrene. Nevertheless, because of the extremely aggressive nature of Fournier gangrene clinicians should keep a low threshold for considering the diagnosis to provide prompt treatment and thus improve survival rates.^2,4

Summary

Fournier gangrene is a rare form of necrotising fasciitis affecting the genitals, perineum and perianal tissues with a high rate of mortality. The diagnosis of Fournier gangrene can be challenging, particularly early on in the disease but is imperative as early treatment with antibiotics, management of sepsis and surgical debridement is required to reduce fatalities in this serious and aggressive disease.