Introduction to fournier gangrene

Necrotizing fasciitis (flesh-eating disease) is a type of necrotizing soft tissue infection (NSTI) that involves the infection of deep soft tissues. The infection is rare but deadly and causes destruction of the muscle fascia and overlying subcutaneous fat. Fournier gangrene is a polymicrobial necrotizing fasciitis of the perineum, genital region, and perianal regions that spreads rapidly. It is more commonly seen in males than in females. Fournier Gangrene is associated with high morbidity and mortality, and prompt diagnosis and treatment are of vital importance as understanding the condition can allow us to recognize the early signs and symptoms for timely intervention to improve outcomes. This article will explore what Fournier Gangrene is and how it develops. 

What is fournier gangrene?

Fournier gangrene is a necrotizing fasciitis, a type of necrotizing soft tissue infection (NSTI). NSTI is an infection that causes the death of the soft tissues, known as necrosis, which involves all the layers of the skin, subcutaneous tissue, fascia, which is the tissue layer that covers the muscles, and the muscle. Necrotizing fasciitis, also known as the ‘flesh-eating disease,’ is a subset of this infection that is characterized by the continuous destruction of the muscle fascia and the subcutaneous fat. Over several days, the infection spreads rapidly along the fascia. 

Fournier gangrene is a rare type of necrotizing fasciitis that affects the perineum, anal, scrotal, and genital regions. Gangrene is the death of body tissue due to a serious bacterial infection or reduced blood supply. Fournier Gangrene has a high fatality rate of 40% and is associated with serious complications like sepsis.¹

Fournier Gangrene is usually seen in 50-70-year-old men with an associated disease, especially diabetes mellitus. The male-to-female ratio of Fournier Gangrene is approximately 10:1. Some other predisposing factors are:

• End-stage kidney or liver failure 
• Hypertension
• Immunosuppression
• Obesity (BMI > 30)
• Alcoholism
• Smoking
• Debility 
• HIV
• Diabetes²

The initial spread of the infection occurs within the fascia and soft tissues, and the skin manifestations only occur at a later stage. This makes Fournier Gangrene easy to miss in the earlier stages of the infection, making early recognition very important to treat the gangrene on time.

Fournier gangrene in women

Fournier Gangrene can also occur in women, although it is much more commonly observed in the male population. When it is seen in women, the outcomes are much poorer, with higher mortality and longer hospital stays.

The risk factors of Fournier Gangrene in women are diabetes mellitus, cardiovascular disease, and obesity. Local infection of the perianal region or abscesses of the vulva also contribute to the development of necrotizing fasciitis. 

The pathophysiology of the Fournier Gangrene remains much the same, except that the origin of the infection in women is commonly vulvar pathologies.

Etiology and microbiology

Necrotizing infection is divided into 2 types: polymicrobial (type I) and monomicrobial (type II). Fournier Gangrene is a polymicrobial (type I) necrotizing infection. There is usually a mix of aerobic and anaerobic species, Enterobacteriaceae, and facultative anaerobic streptococci. Swabs from the wound site most commonly culture microorganisms like E. coli, Klebsiella, Proteus, Staphylococcus, and Streptococcus. Most of the microorganisms found on the wound are bacteria that normally live on our skin, also known as commensal organisms. 

Bacteria can enter the body to cause infection in several different ways. It usually happens when the skin is injured, allowing an opening for the bacteria to enter. Some situations in which this occurs in Fournier Gangrene are:

• Abscess
• Anal fistula, diverticulitis
• Genital piercing
• Infection of the bladder or urinary tract
• Scratch or burn injuries
• Insect bites
• Rectal cancer
• Sex
• Ulcer³

Pathophysiological mechanisms

The pathophysiology of Fournier Gangrene is a combination of injury, bacterial invasion and spread, toxin production, vascular thrombosis, and tissue necrosis. 

Bacterial invasion and spread

An initial insult or damage to the perineal region by way of trauma or other reasons causes an opening in the skin. The breach in the skin barrier allows the introduction of bacteria into the soft tissues, particularly the fascia. The polymicrobial infection can spread not only to the perineal and genital regions but also to the anterior abdominal wall due to the anatomical structure of the fascia that covers the muscles in the area. The spread of infection occurs along the fascial planes and can involve the scrotum, penis, up the anterior abdominal wall, and even up to the clavicle. As the testis is located intraabdominally, it is often spared.⁴

Toxin production and tissue destruction

The nature of the infection is polymicrobial, with upwards of four organisms being cultured from each patient. The combined activity of the various bacteria leads to the production of different types of exotoxins and enzymes that aid in the necrosis of tissue and the spread of infection. Through a complex series of immunological events that occur due to this infection, blood clots in the smaller vessels called microvascular thrombi are formed. The thrombi plug up the vessels, leading to impaired blood flow to the tissue in the area, resulting in necrosis.⁴ 

In further detail, the aerobic bacteria produce the heparinase enzyme, which causes platelet aggregation and complement fixation, which leads to coagulation and blood clots. The resulting impaired blood flow leads to a low oxygen environment and subsequent oxygen deprivation of tissue called hypoxia. The lack of oxygen further encourages the proliferation of anaerobic bacteria within the polymicrobial mix. The spread of infection is further aided by these anaerobic bacteria as they produce enzymes that digest fascia. These bacteria also produce gas and enzymes, detectable as subcutaneous crepitus, which is a crackling sensation under the skin. Moreover, other microorganisms like bacteria inhibit phagocytosis, which is the ingestion and digestion of bacteria by the immune cells called phagocytes in our body, further assisting infection spread.⁵

Sepsis 

Sepsis is a life-threatening reaction that occurs when the body’s immune system overreacts to an infection. When the local infection spreads systematically in Fournier Gangrene, it leads to a cascade of inflammatory response that ends with organ damage. The necrosis of tissue and the abundant presence of bacteria and their toxins lead to bacteremia, which is the presence of bacteria in the blood. The bacteremia triggers the immune system to release a large amount of inflammatory mediators, overwhelming the body. Sepsis can lead to devastating conditions such as septic shock and multiple organ dysfunction syndrome (MODS).

Complications of fournier gangrene

Fournier Gangrene can result in severe complications. Some of the complications are:

• Septic shock 
• Diabetic ketoacidosis (DKA) in patients with diabetes 
• Disseminated intravascular coagulation (DIC)
• Acute kidney injury (AKI)
• Multiple organ failure
• Prolonged hospital admission⁶

Recognition and management of fournier gangrene 

The early signs of Fournier Gangrene include fever, general discomfort (malaise), pain, and swelling in the perineal region. Fever and lethargy may precede visible skin changes by 2–7 days. The skin may not reflect the severity of the disease. The infected tissue may produce a very unpleasant smell (fetid suppuration) and eventually progress to become a fulminant gangrene. A crackling sound and sensation may be felt under the skin (crepitus) as the gas in the wound moves when the affected area is rubbed.

Fournier Gangrene is suspected if the genitalia and perineum show soft tissue crepitation and localized tenderness of the wound. Ultrasound and computed tomography (CT) imaging methods may aid in the diagnosis of Fournier Gangrene, but if the condition is suspected, investigation should not delay surgical treatment. Treatment may involve aggressive resuscitative methods and intravenous antibiotics followed by urgent surgical debridement (removal) of necrotic skin and tissue.^6,7

Summary

Fournier Gangrene is a rare but life-threatening form of necrotizing fasciitis that affects the perineal, genital, and perianal regions. It is a polymicrobial infection that spreads rapidly and causes skin and tissue necrosis. It is associated with high mortality rates, particularly in people with underlying health conditions such as diabetes mellitus and obesity. The pathophysiology of Fournier Gangrene begins with the compromise of the skin barrier and subsequent invasion of commensal bacteria that leads to the production of toxins and enzymes. This series of events eventually leads to tissue death. Severe complications can arise from Fournier Gangrene, such as septic shock and multiple organ failure. Early recognition is vital, as prompt intervention with antibiotics and surgical treatment can be critical in improving outcomes.