Fournier gangrene overview
Steven C. Campbell, M.D., Ph.D.; Associate Editor(s)-in-Chief:  Yamuna Kondapally, M.B.B.S; Jesus Rosario Hernandez, M.D. 

# Overview
Fournier gangrene is a type of synergistic polymicrobial necrotizing infection (gangrene) of the perineal, genital or perianal regions usually affecting the male genitals but can also occur in females and children. It is a fulminant form of necrotizing fasciitis. It was first described by Baurienne in 1764 and is named after a French venereologist, Jean Alfred Fournier following five cases he presented in clinical lectures in 1883.

# Historical Perspective
Fournier gangrene was first described in 1764 by Baurienne. The detailed description of Fournier gangrene was given by Jean Alfred Fournier, a French venereologist, in 1883.

# Classification
The ICD 10 classification of Fournier gangrene include: ICD-10: N49.3, code Classification, diseases of the genitourinary system, diseases of male genital organs (N40-N53), inflammatory disorders of male genital organs, NEC (N49).

# Pathophysiology
The transmission of pathogens occurs through the following routes: External trauma, direct spread from a perforated viscus, Urogenital organ, perirectal abscess, and decubitus ulcer. Following transmission, the bacteria uses the entry site to invade the fascial planes which causes the wide spread necrosis of superficial fascia, deep fascia, subcutaneous fat, nerves, arteries, and veins. Superficial skin and deeper muscles are typically spared. In late stages, lesions develop liquefactive necrosis at all tissue levels. The development of cutaneous and subcutaneous vascular necrosis leads to local ischemia and further bacterial proliferation. The infection spreads from superficial (colles fascia) and deep fascial planes of genitalia to the overlying skin sparing the muscles. The infection then spreads from colles fascia to the penis and scrotum via Buck's and Dartos fascia or to the anterior abdominal wall via Scarpa's fascia or vice versa. The inferior epigastric and deep circumflex iliac arteries supply the anterior abdominal wall, and the deep external pudendal and internal pudendal arteries supply the scrotal wall. Except for the internal pudendal artery, each of these vessels travels within Camper's fascia and can therefore become thrombosed in the progression of Fournier gangrene. The common locations of Fournier gangrene are perineum, scrotum, and penis. On gross pathology, the characteristic findings of Fournier gangrene include: Subcutaneous emphysema, swollen scrotal wall, edema, erythema, bullae, skin sloughing. On microscopic histopathological analysis, the characteristic findings of Fournier gangrene are Obliterative vasculitis with microangiopathic thrombosis, acute inflammation of subcutaneous tissue, superficial hyaline necrosis along with edema and inflammation of the dermis and subcutaneous fat, dense neutrophil-predominant inflammatory infiltrate, noninflammatory intravascular coagulation and hemorrhage, and myonecrosis.

# Causes
Fournier gangrene is caused by mixed aerobic and anaerobic organisms which normally exist below the pelvic diaphragm in the perineum and genitalia. Fournier gangrene may be caused by the following organisms:

# Differentiating Fournier gangrene from Other Diseases
Fournier gangrene must be differentiated from other diseases that cause pain, swelling, erythema, discharge and raised temperature (fever) such as: Scrotal abscess, herpes simplex, cellulitis, strangulated hernia,streptococcal necrotizing fasciitis, Gonococcal balanitis and edema, vascular occlusion syndromes, Allergic vasculitis, pyoderma gangrenosum, necrolytic migratory erythema, ecthyma gangrenosum, warfarin necrosis, and polyarteritis nodosa.

# Epidemiology and Demographics
The overall incidence of Fournier gangrene annually is 1.6 cases per 100,000 males. The incidence peaked and remained steady after age 50 at 3.3 cases per 100,000 males. Fournier gangrene affects individuals of all ages but more commonly affects individuals older than 50 years of age.. Men are more commonly affected with Fournier gangrene than women, with a male:female ratio of 10:1.. Mortality rate decreases with early aggressive treatment. The mortality rate of Fournier gangrene is between 20% to 80%. Higher mortality rates are found in daibetics, alcoholics and those with colorectal sources of infection.

# Risk Factors
Common risk factors in the development of Fournier gangrene include:  Age >50 years, male gender, diabetes mellitus, alcohol misuse, immunosupression, chemotherapy, chronic corticosteroid use, HIV, leukemia, liver disease, debilitating illness, malignancy, cytotoxic drugs.

# Screening
According to the U.S. Preventive Service Task Force (USPSTF), there is insufficient evidence to recommend routine screening for Fournier gangrene.

# Natural History, Complications, and Prognosis
If left untreated, the acute inflammatory changes spread quickly, accompanied by high fever and extreme weakness. The overlying skin becomes smooth, tense and shiny and diffuse erythema without distinct borders are seen. During the first 1 or 2 days, the lesions develop with progressive color changes from red to purple to blue and then become gangrenous, first turning black, then greenish yellow. If the patient has survived, a line of demarcation between viable and necrotic tissue would become sharply defined from days 7 to 10. Sloughing of necrotic skin would reveal the underlying pus and extensive liquefactive necrosis of subcutaneous tissues, which will be significantly more extensive than would be suspected with the overlying area of necrotic skin. Metastatic abscesses and pulmonary distress may develop as well. Common complications of Fournier gangrene include: Renal failure, acute respiratory distress syndrome, heart failure, cardiac arrhythmias, septic metastasis, urinary tract infection, stroke, acute thromboembolic disease of lower extremities, wound infection, prolonged ileus (7 days), and eventration or evisceration. Depending on the underlying comorbidities, the prognosis of Fournier gangrene varies. Some of the prognostic factors include: Presence of severe sepsis and whether the affected area calculation/extension of the necrosis is 5% of the body surface area.

# Diagnosis

## Diagnostic Criteria
The diagnosis of Fournier gangrene is primarily based on clinical findings. The diagnosis is based on following criteria: Soft tissue infections with involvement of the scrotum, perineum and perianal areas, presence of air infiltrating the subcutaneous tissue (demonstrated by physical examination or radiological findings), surgical findings of gangrenous and necrotic tissue, histologically proven necrotizing fasciitis.

## History and sympotoms
Specific areas of focus when obtaining a history from the patient include trauma, alcohol misuse, immunosupression, chemotherapy, chronic corticosteroid use, and HIV infections. The symptoms of Fournier gangrene include: Pain and swelling in the scrotum, erythema, discoloration of involved skin, Purulence or wound discharge, pallor, and fever >38C.

## Physical examination
In the physical examination of Fournier gangrene, the patients with Fournier gangrene usually appear to be ill. *Tachycardia and hypotension are mostly present and the skin may show evidence of trauma, surgery, insect or human bites, or injection sites. Ppalpation of genitalia and perineum, and digital rectal examination may reveal induration, eryhthema, swelling, erythema with ill defined margins, blistering/bullae, skin discoloration, foul discharge (greyish or brown discharge), and fluctuance

## Laboratory Findings
The most important laboratory findings in necrotizing fasciitis include C-reactive protein, total white blood cell count, Hemoglobin, Sodium, Creatinine, Glucose. The main importance of these laboratory findings are due to their usage as a distinguishing method for differentiating necrotizing fasciitis from other soft tissue infections.

## X ray
On X-ray, Fournier gangrene is characterized by subcutaneous gas or soft tissue swelling (specific x-ray finding) seen extending from scrotum and perineum to the inguinal regions, anterior abdominal wall, and thighs, and increase in the soft tissue thickness and opacity.

## Computed tomography
The CT of Fournier gangrene is characterized by  soft tissue stranding and fascial thickening, soft tissue gas, the extent of disease can be assessed prior to surgery with a cause of infection may be apparent (e.g.perineal abscess, fistula).

## MRI
On MRI, Fournier gangrene is characterized byedema and inflammation of skin and subcutaneous planes of the scrotum and perineal planes and Subcutaneous emphysema

## Ultrasound
On ultrasound, Fournier gangrene is characterized by: Thickened scrotal wall, echogenic gas foci in scrotum pathognomonic (seen as dirty shadowing), testes and epididymi spared (due to their separate blood supply), reactive unilateral or bilateral hydroceles are present, differentiate Fournier gangrene from inguinoscrotal incarcerated hernia (In inguinoscrotal incarcerated hernia gas is observed in the obstructed bowel lumen, away from the scrotal wall).

# Treatment

## Medical Therapy
Fournier gangrene is a urological emergency requiring intravenous antibiotics and debridement (surgical removal) of necrotic (dead) tissue. Despite such measures, the mortality rate overall is 40%, but 78% if sepsis is already present at the time of initial hospital admission. The spread of gangrene is rapid at the rate of 23 cm/h, hence early diagnosis and emergency surgical treatment is important.

## Surgery
Surgery is the mainstay of treatment for Fournier gangrene.. As the patients are cardiovascularly unstable, immediate resuscitation with intravenous fluids, colloids and inotropic agents are usually necessary.

## Prevention
Primary prevention
Effective measures for the primary prevention of Fournier gangrene include prevention of trauma/breaks in skin integrity that act as a portal of entry, treatment of cellulitis to prevent extension into the subcutaneous tissue, ensure wounds are cleaned and monitored for signs of infection, do not delay first aid of wounds like blisters, scrapes, or any break in the skin, patients with underlying co-morbidities should watch carefully for any signs of infection.
Secondary prevention
Secondary prevention strategies following Fournier gangrene include early diagnosis and prompt treatment with either antibiotics or surgery. This strategy prevents or slows the progression and complications of the disease.