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Fournier’s gangrene (FG) is an infectious, rapidly progressive necrotizing fasciitis which is considered a urological emergency for its life-threatening nature. It affects small subcutaneous vessels, with vascular thrombosis leading to tissue necrosis. It was first described by Baurienne in 1764 and later named by the parisien venereologist Jean Alfred Fournier in 1883 (Wróblewska et al. 2014; Yılmazlar et al. 2014; Voelzke and Hagedorn 2018; Smith et al. 1998)
Fournier’s gangrene is relatively rare, with an overall incidence that ranges from 1.6 to 3.3 /100000 males (Wróblewska et al. 2014).
It is more frequent in the adult population (Wróblewska et al. 2014; Yılmazlar et al. 2014; Voelzke and Hagedorn 2018; Üreyen et al. 2017; Smith et al. 1998), but sporadic cases are reported also in children (Wróblewska et al. 2014).
It occurs more frequently in men than in women, with a male–female ratio of 10:1, both for the better drainage of the perineal area by vaginal secretion and possibly for the under-diagnosis of this condition in female patients (Wróblewska et al. 2014; Voelzke and Hagedorn 2018; Yılmazlar et al. 2014; Üreyen et al. 2017; Smith et al. 1998).
Fournier’s gangrene can occur in genital, perineal, and perianal region. Usually the first site of involvement is the scrotum, with a rapid spread of the infection to the penis and perineal tissues. In the worst cases, the process can affect also the anterior abdominal wall and infiltrate the soft subcutaneous tissue up to the clavicle (Wróblewska et al. 2014; Yılmazlar et al. 2014; Voelzke and Hagedorn 2018; Üreyen et al. 2017; Smith et al. 1998).
Fournier’s gangrene is still nowadays a urological emergency that requires a multidisciplinary approach. The treatment of choice is the combination of early surgical debridement of the necrotic tissue with a wide excision and antibiotic therapy, often based on the microbiological analysis of the resected material. Other therapies can be used to improve the clinical outcome, such as hyperbaric oxygen and the topic application of substances such as unprocessed honey, sodium hypochlorite or lyophilized collagenase (Wróblewska et al. 2014; Voelzke and Hagedorn 2018; Yılmazlar et al. 2014; Üreyen et al. 2017; Smith et al. 1998).
Despite early and aggressive treatments, the mortality of FG remains very high, between 20% and 45%, white a range of 4–80% (Wróblewska et al. 2014; Yılmazlar et al. 2014). Overall, there are several score systems that are used to predict the risk of mortality of the patients. The most frequently employed are Fournier’s Gangrene Severity Index (FGSI) and Uludag Fournier’s Gangrene Severity Index (UFGSI). All the score systems are based on clinical and laboratory parameters, with FGSI evaluating temperature of the patient, heart and respiratory rates, serum levels of potassium, sodium and venous bicarbonate, creatinine, hematocrit and white blood count, while UFGSI integrating these variables with the extension of the infection (disease confined to urogenital or/and anorectal region, pelvic area, or extended beyond pelvic area) and the age of the patient (with 60 years as a cut off). Parameters are summed up and the result is a number which is related to a significantly different outcome, with a cut off of >6 for FGSI and >8 for UFGSI (Üreyen et al. 2017).
On gross examination, the subcutaneous tissue shows necrotic areas, with presence of purulent material, surrounded by edema. As the disease spreads, the skin begins to be involved, with the presence of redness in early stages, followed by swelling and ulceration in late stages (Wróblewska et al. 2014; Yılmazlar et al. 2014; Voelzke and Hagedorn 2018; Smith et al. 1998).
Necrotizing soft tissue infections are categorized into four types based on the different microorganisms responsible for the disease. Type 1 infections are the most common, associated with a polymicrobial population of bacteria. Type 2 diseases are related to monomicrobial agents, mostly represented by group A beta-hemolytic Streptococcus. Type 3 infections are rare, representing less than 5% of necrotizing soft tissue infections, and are associated to Vibrio species or Gram-negative bacteria, while type 4 infections are caused by fungal microorganisms (Voelzke and Hagedorn 2018).
Fournier’s gangrene is classified as type 1 necrotizing fasciitis. Bacteria involved can be enteric rods (Escherichia coli, Klebsiella spp., Proteus spp.) Gram-positive (staphylococci, streptococci, enterococci) and obligate anaerobic bacteria (Clostridium spp., Bacteroides spp., Fusobacterium spp., Peptococcus spp., Peptostreptococcus spp.), which are usually part of the normal urogenital and anogenital flora. Recently, community-acquired methicillin-resistant S. aureus (CA-MRSA) has emerged as an etiological agent responsible for a severe form of the disease related to rapidly progressive course and, in some cases, even fulminant sepsis (Wróblewska et al. 2014; Voelzke and Hagedorn 2018).
The most characteristic feature is the presence of obliterative endarteritis, with thrombosis of small vessels.
At higher magnification, acute inflammation represented by neutrophils infiltrate is seen, in addition to bacterial colonization of the tissue and necrosis. The process is confined to the penile fascia, with deep erectile tissue usually spared (Wróblewska et al. 2014; Yılmazlar et al. 2014; Voelzke and Hagedorn 2018; Üreyen et al. 2017; Smith et al. 1998).
Immunohistochemistry is not routinely performed, as the diagnosis is correctly reached with the H&E stain. However, histochemical Gram stain can show the extensive bacterial colonization of the tissue.
Even though the correct diagnosis is quite well achieved through the clinical and laboratory data of the patient, some entities may mimic Fournier’s gangrene, and it is mandatory to exclude them for a correct management of the patient.
Usually, imaging can help in making the correct diagnosis. Indeed, ultrasonography (US) is good to discriminate Fournier’s gangrene from inguinoscrotal hernias, as in the former condition presence of gas is seen in the scrotal wall, while in the latter the gas is present in the bowel wall, far from the scrotum. Moreover, US can help distinguish Fournier’s gangrene from cellulitis, for the lacking of gas in soft tissue in the latter condition.
Some lesions can have an infectious origin as Fournier’s gangrene, but the microbiological analysis can reveal different agents, as in streptococcal necrotizing fasciitis, herpes simplex virus infection, gonococcal balanitis, and Corbus disease.
Some conditions that mimic Fournier’s gangrene have a traumatic origin, such as fracture or hematoma of the testicle, or extra-testicular injuries as hematomas, torsion of the spermatic cord, strangulated scrotal hernia, and blood extravasation derived from testicular tumors, so the clinical history of the patient is very important.
Finally, gangrene in genital area could be a sign of systemic diseases. Indeed, patients with diabetes have more frequently small vessels obliterative disorders, and also patients with IgE-related hypersensitivity vasculitis, polyarteritis nodosa, and immunovasculitis can develop gangrene in this area (Smith et al. 1998).