Introduction

Named after the French venereologist, Jean Alfred Fournier, Fournier’s gangrene is necrotising fasciitis of the perineum, external genitals and perianal areas.¹ Necrotising fasciitis is widely described as a “flesh-eating disease”. It is an infection that leads to a low flow in small blood vessels of the skin, and soft tissues, causing cell death and gangrene. Gangrene leads to the release of a “soup” of toxic chemicals that cause tissue inflammation and further damage. 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, arterial damage and gangrene leads to a rapidly progressive and destructive disease that eats away at the soft tissues and is frequently fatal.²

Fournier’s gangrene is predominantly a disease of people assigned male at birth (AMAB), with an incidence of 1.6 per 100,000 people AMAB. Its occurrence in people assigned female at birth (AFAB) is rare, with a ratio of 10:1 between cases found in people AMAB: people AFAB.³ Nevertheless, studies of Fourniere’s gangrene in people with AFAB demonstrate higher rates of mortality and increased length of hospital stay, compared with people with AMAB. 

In a study of 134 cases of Fournier’s gangrene in people AFAB, the death rate was 20% of cases (but has been estimated to be up to 50% in other studies) compared to 7.5% in people AMAB.⁴ The absence of early clinical signs and delays in initial presentation to the hospital, as well as a low index of suspicion owing to the rarity of Fournier’s gangrene in people AFAB, are believed to be possible contributing factors to the relatively higher rates of mortality in people AFAB.⁴

Fournier’s gangrene is a surgical emergency. Initial management with intravenous antibiotics, stabilisation of sepsis (septicaemia) and surgical debridement (cutting away) of gangrene is imperative to reduce mortality and extensive tissue destruction. Because Fournier’s gangrene is an extremely aggressive and rapidly spreading disease, timely diagnosis is required to institute these measures as early as possible.

Causes and risk factors

Fournier’s gangrene initially begins with bacteria entering from the skin of the perineum, perianal area or external genitalia. In people with AFAB, the source is usually an infection of the perineum or vulva (external genitalia).  Of these infections, abscesses in the peri-anal region are the most common, abscesses of the vulva, including Bartholin’s cyst abscesses (abscesses of the vaginal lubricating glands) the next most common, with other causes of localised infection, such as trauma to the genital area, local radiotherapy for cancer and complications from previous surgery to the perineal/vulvar region making up the remainder of cases.⁴ 

In Fournier’s gangrene, infection is usually with a combination of multiple types of bacteria which, whilst causing less severe infections on their own, combine to cause the release of toxic chemicals that precipitate the blockage of small blood vessels and gangrene in necrotising fasciitis.² It usually occurs in the presence of a weakened immune system. Diabetes is the most common risk factor, followed by alcoholism (a more common risk factor in people AMAB), obesity and cardiovascular disease. Less common risk factors include cancer, chemotherapy, the use of corticosteroid drugs, radiotherapy and kidney and liver disease. In the previously mentioned study of 134 cases in people AFAB, 44% had diabetes, 25% had cardiovascular disease and 16% were found to be obese.⁴

Clinical presentation

Initial clinical presentation of Fournier’s gangrene is with pain, redness (erythema) and swelling in the perineal region. Typically, pain is more severe than external clinical findings might suggest. Skin changes may be minimal or progress from redness, to patchy purple changes, bullae (blisters), or black skin discolouration indicating gangrene. As the disease advances, skin changes become more apparent and may be extensive, even involving the anterior abdominal wall or limbs. Crepitus is the feeling of crackling in the skin due to bubbles of gas produced by gas-forming bacteria and may be present as gangrene develops in the soft tissues.⁵

Generalised symptoms may include feeling generally unwell (malaise), vomiting, nausea and fever. If sepsis (septicaemia) is present due to the infection this may present with septic shock - symptoms and signs include pallor, clammy skin, cold extremities, rapid pulse rate, low blood pressure and multi-organ failure leading to reduced consciousness level.⁵ In people with AFAB, the most common symptoms at presentation are localised redness and cellulitis (42%), Peripheral pain (40%) and septic shock (28%).⁴

Diagnostic approaches

Physical examination findings

Examination of the perineum and external genitalia should be remembered in people in whom this is often neglected, including people with severe obesity, spinal injuries or paraplegia, people with dementia and those with difficulties with verbal communication. General examination may reveal signs of septic shock, such as a weak, rapid pulse, low blood pressure, cold extremities and drowsiness.^4,5  

Laboratory markers

Baseline blood tests should be taken for full blood count, C-reactive protein (a marker of inflammation), blood gasses (to assess the blood acid-base balance), renal profile and liver profile and blood clotting studies.⁶ 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, however, it should not be used in isolation to exclude necrotising fasciitis.⁷

Whilst antibiotics should be started as soon as possible, without waiting for the results of microbial tests, microbial tests including blood cultures, urine cultures and cultures from swabs of wound or abscess discharge should be taken and the antibiotic regime can be tailored to the results of these tests once they are available.⁸

Imaging techniques

X-rays of the abdomen and pelvis can be used to detect the presence of gas in the soft tissues, which occurs in gangrene and may be seen on X-rays before the clinical sign of crepitus is apparent. However, the absence of gas on the x-ray does not exclude Fournier’s gangrene.⁹

Ultrasound scanning is more useful in the assessment of Fournier’s gangrene in people AMAB, where it is not only helpful in detecting gas within the scrotum, or the scrotal wall, but also in distinguishing other causes of scrotal/perineal pain, such as testicular problems or hernias. As CT scanning is superior to ultrasound scanning it is the investigation of choice in imaging Fournier’s gangrene in people AFAB.⁹

CT scanning may also reveal the presence of gas in the soft tissues (called surgical emphysema), as well as thickening of the soft tissues. Inflammation around the sheets of fibrous tissue called fascia that separate the soft tissue into compartments is seen as uneven thickening of the fascia on a CT scan. CT scanning may also demonstrate the primary source of the infection, such as a peri-anal fistula or abscess, or other collections of pus or infection within the pelvic cavity. Because CT scanning provides excellent information on the extent of the disease, it can be used in planning surgical treatment and assessing the formation of new disease after initial surgery to remove gangrenous tissue.⁹

Whilst magnetic resonance imaging (MRI) provides excellent images of the soft tissues, it is not traditionally the investigation of choice in Fournier’s gangrene because undue delay in obtaining MRI scans is undesirable if it delays prompt surgical treatment.⁹

Management strategies

Initial stabilisation

Especially if septic shock is present, patients with Fournier’s gangrene require supportive treatment with intravenous fluids to manage sepsis and fluid management (this may include inserting a urinary catheter to monitor fluid output). Patients with severe sepsis may require the opinion of an intensive care doctor, and management in the intensive care unit.¹⁰

A cocktail of intravenous antibiotics designed to cover the likely organisms that are implicated in infection in Fournier’s gangrene should be commenced immediately. The exact antibiotics used will depend on local hospital guidelines and any allergies each person may have. Once the results of blood cultures and wound swab cultures are available, antimicrobial treatment can be tailored to the results of these investigations.^8,10

Because diabetes is the most commonly found predisposing condition in Fournier’s gangrene, patients may also present with poorly controlled diabetes, or in some cases, a diabetic emergency called diabetic ketoacidosis.¹¹ 

Other conditions that may require special management in Fourniere’s gangrene may include organ failure eg. kidney failure (either present as a predisposing factor or brought on by septic shock), alcohol dependence, complications of malignancy and other immunocompromised states, such as HIV. Multidisciplinary input, with contributions from endocrine specialists, intensivists (intensive care specialists), general surgical, urological, obstetrics and gynaecology or plastic surgery input, may all be required to determine optimum management.

Surgical interventions

Surgical debridement (cutting away) of gangrenous tissue is the mainstay of surgical management. This involves the removal of all affected skin and soft tissue (fat, muscle and fascia) until the margin of healthy tissue is reached. In some cases this may necessitate the removal of extensive sections of tissue, leaving a large open wound. The area must be thoroughly explored during surgery as gangrene may form in the deeper tissues and is not always superficially apparent. Many patients will have to undergo more than one surgical debridement as gangrenous tissue may continue to form following initial debridement with repeat exploration and debridement every 12-48 hours.^12,13

 Tissue samples should be taken for microscopic examination to confirm the diagnosis of necrotising fasciitis, and also for further microbiological culture. Following debridement the area can either be dressed with traditional dressings or a negative pressure dressing, which is a traditional wound dressing connected to a vacuum pump device that exposes the wound to negative pressure.^12,13 Granulation tissue, a thickened, moist tissue with a “cobblestone” appearance, rich in inflammatory and white cells, forms over the open wound in the first stage of wound healing. Specialist wound care and dressing are required in the early postoperative period.

Surgical procedures to divert faeces and urine

To prevent faecal contamination of the post-operative wound, a diversion colostomy may need to be performed. In this procedure the colon is brought out through an opening in the abdomen called a colostomy.¹⁴ To prevent urinary contamination of the wound, a suprapubic catheter (a urinary catheter inserted through the abdomen directly into the bladder) may be placed.

Hyperbaric oxygen therapy

The use of hyperbaric oxygen therapy (a procedure in which the person is placed in a tank of high-pressure oxygen), in conjunction with medical and surgical measures, has been shown to reduce the lengths of hospital stay and reduce, overall mortality rates in some studies.¹⁵  

Reconstructive surgery

Cosmetic reconstruction of the perineum is not undertaken until the area is healed. Various procedures may be employed in cosmetic reconstruction, including skin grafts and flaps. In people with AFAB, this may involve a multidisciplinary approach with input from general surgery, obstetrics and gynaecology, and plastic surgery.¹⁶

Summary

Fournier’s gangrene is a rare condition in people AFAB (assigned female at birth) compared with people assigned male at birth. People AFAB have higher death rates and average lengths of hospital stay. Early detection and prompt treatment with surgery, antibiotics and management of septic shock are required to reduce mortality and tissue destruction from this potentially devastating disease.