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Necrotizing Fasciitis

Author: Michael Maynor, MD, Clinical Assistant Professor, Department of Hyperbaric/Emergency Medicine, Louisiana State University School of Medicine
Contributor Information and Disclosures

Updated: Mar 25, 2009

Introduction

Background

For more than a century, many authors have described soft tissue infections. Their occurrence has been on the rise because of an increase in immunocompromised patients with diabetes mellitus, cancer, alcoholism, vascular insufficiencies, organ transplants, HIV, or neutropenia.

Necrotizing fasciitis can occur after trauma or around foreign bodies in surgical wounds, or it can be idiopathic, as in scrotal or penile necrotizing fasciitis.

Necrotizing fasciitis has also been referred to as hemolytic streptococcal gangrene, Meleney ulcer, acute dermal gangrene, hospital gangrene, suppurative fascitis, and synergistic necrotizing cellulitis. Fournier gangrene is a form of necrotizing fasciitis that is localized to the scrotum and perineal area.

Necrotizing fasciitis is a progressive, rapidly spreading, inflammatory infection located in the deep fascia, with secondary necrosis of the subcutaneous tissues. Because of the presence of gas-forming organisms, subcutaneous air is classically described in necrotizing fasciitis. This may be seen only on radiographs or not at all. The speed of spread is directly proportional to the thickness of the subcutaneous layer. Necrotizing fasciitis moves along the deep fascial plane.

These infections can be difficult to recognize in their early stages, but they rapidly progress. They require aggressive treatment to combat the associated high morbidity and mortality.

The causative bacteria may be aerobic, anaerobic, or mixed flora, and the expected clinical course varies from patient to patient.

Pathophysiology

Most necrotizing soft tissue infections have anaerobic bacteria present, usually in combination with aerobic gram-negative organisms. They proliferate in an environment of local tissue hypoxia in those patients with trauma, recent surgery, or medical compromise.

Facultative aerobic organisms grow since polymorphonuclear (PMN) leukocytes exhibit decreased function under hypoxic wound conditions. This growth further lowers the oxidation/reduction potential, enabling more anaerobic proliferation and, thus, accelerating the disease process.

Carbon dioxide and water are the end products of aerobic metabolism. Hydrogen, nitrogen, hydrogen sulfide, and methane are produced from the combination of aerobic and anaerobic bacteria in a soft tissue infection. These gases, except carbon dioxide, accumulate in tissues because of reduced water solubility.

In necrotizing fasciitis, group A hemolytic streptococci and Staphylococcus aureus, alone or in synergism, are frequently the initiating infecting bacteria. However, other aerobic and anaerobic pathogens may be present, including Bacteroides, Clostridium, Peptostreptococcus, Enterobacteriaceae, coliforms, Proteus, Pseudomonas, and Klebsiella.

Bacteroides fragilis is usually noted as part of a mixed flora in combination with Escherichia coli. B fragilis does not directly cause these infections, but it does play a part in reducing interferon production and the phagocytic capacity of macrophages and PMNs.

A variant synergistic necrotizing cellulitis is considered to be a form of necrotizing fasciitis, but some authorities feel that it is actually a nonclostridial myonecrosis. This condition begins in the same manner as necrotizing fasciitis, but it progresses rapidly to involve wide areas of deeper tissue and muscle at an earlier stage than might be expected. Severe systemic toxicity occurs.

Anaerobic streptococci, occasionally seen in intravenous drug users, cause many forms of nonclostridial myonecrosis. Some cases of necrotizing fasciitis can be caused by Vibrio vulnificus. This organism is seen more often in patients with chronic liver dysfunction, and it often follows the consumption of raw seafood. V vulnificus may cause subcutaneous bleeding.

Frequency

United States

Since 1883, more than 500 cases of necrotizing fasciitis have been reported in the literature.

International

There may be an increased incidence in African and Asian countries; however, because of the lack of recorded cases, the true incidence is not known.

Mortality/Morbidity

The overall morbidity and mortality is 70-80%.

• Fournier gangrene has a reported mortality as high as 75%.
• The mean age of survivors is 35 years.
• The mean age of nonsurvivors is 49 years.

A retrospective review by Cheng et al showed that upper extremity necrotizing fasciitis has a high mortality rate. In their review, about 35% of patients died. A state of altered consciousness and respiratory distress at initial presentation were found to be statistically significant factors for eventual mortality. Early diagnosis and referral for aggressive surgical treatment prior to the development of systemic toxic signs are essential for survival.¹

Mao et al retrospectively reviewed 660 patients with craniocervical necrotizing fasciitis. Data were collected on 20 patients who met inclusion criteria; 10 of these patients had thoracic extension and 10 did not. The survival rate for the group with thoracic extension was 60% (6 of 10) compared with 100% for the group without thoracic extension. Lower overall survival for the patients in the thoracic extension group is likely attributed to older age of the patient, existing increased comorbidity, more surgical debridement was required, and increased postoperative complications. Overall survival of the patients with craniocervical necrotizing fasciitis without thoracic extension can be attributed to aggressive wound care and surgical debridement, broad-spectrum intravenous antibiotics, and care in the surgical intensive care unit. Mao et al recommend that hyperbaric oxygen (HBO) therapy be included for those patients who can tolerate it.²

Sex

The male-to-female ratio is 2-3:1.

Age

• The mean age of a patient with necrotizing fasciitis is 38-44 years.
• This disease rarely occurs in children. Pediatric cases have been reported from resource-poor nations where poor hygiene is prevalent.

Clinical

History

• A history of trauma or a recent surgery to the involved area is often present. Idiopathic cases are not uncommon.
• Typically, there is a sudden onset of pain and swelling at the site of trauma or recent surgery. In some cases, the symptoms may begin at a site distant from the initial traumatic insult. Pain may be out of proportion to physical findings.
• Over the next several hours to days, the local pain progresses to anesthesia.
• Fournier gangrene begins with pain and itching of the scrotal skin.
• A history of comorbid factors, including diabetes mellitus, should be sought in all cases of suspected necrotizing fasciitis.
• Diagnosis of necrotizing fasciitis can be difficult and requires a high degree of suspicion.

Physical

• Physical findings may not be commensurate with the degree of patient discomfort; early detection is key.
• The patient usually appears moderately to severely toxic, but early on, the patient may look deceptively well.
• Typically, the infection begins with an area of erythema that quickly spreads over a course of hours to days.
• The redness quickly spreads, and the margins of infection move out into normal skin without being raised or sharply demarcated.
• As it progresses, the infection gives way to dusky or purplish skin discoloration near the site of insult.
  • Multiple identical patches develop to produce a large area of gangrenous skin, as the erythema continues to spread.
  • The initial necrosis appears as a massive undermining of the skin and subcutaneous layer.
  • If the skin is open, gloved fingers can pass easily between the 2 layers and may reveal yellowish-green necrotic fascia. If the skin is unbroken, a scalpel incision will reveal it.
  • The normal skin and subcutaneous tissue are loosened from the rapidly spreading deeper necrotic fascia that is a great distance from the initiating wound.
  • Fascial necrosis is typically more advanced than the appearance suggests.
• Anesthesia in the involved region may be detected, and it usually is caused by thrombosis of the subcutaneous blood vessels, leading to necrosis of nerve fibers.
• Without treatment, secondary involvement of deeper muscle layers may occur, resulting in myositis or myonecrosis. Normally, however, the muscular layer remains healthy red with normal bleeding muscle under the yellowish-green fascia.
• Usually, the most important signs are tissue necrosis, putrid discharge, bullae, severe pain, gas production, rapid burrowing through fascial planes, and lack of classical tissue inflammatory signs.
• Usually, some degree of intravascular volume loss is detectable on clinical examination.
• General signs, such as fever and severe systemic reactions, may be present.
• Local crepitation can occur in more than one half of patients. This is an infrequent finding, specific but not sensitive, particularly in cases of nonclostridial necrotizing fasciitis.
• Fournier gangrene begins with local tenderness, edema, and erythema of the scrotal skin.
  • This progresses to necrosis of the scrotal fascia. The scrotum enlarges to several times its normal diameter.
  • If the process continues beyond the penile-scrotal region to the abdomen or the upper legs, the normal picture of necrotizing fasciitis can be seen.
  • In males, the scrotal subcutaneous layer is so thin that most of the patients present after the skin is already exhibiting signs of necrosis.
  • In 2-7 days, the skin becomes necrotic, and a characteristic black spot can be seen.
  • Early on, this infection may resemble acute orchitis, epididymitis, torsion, or even a strangulated hernia.
  • In women, Fournier gangrene acts more like necrotizing fasciitis because of the thicker subcutaneous layers involving the labia majora and the perineum.

Causes

• Surgical procedures may cause local tissue injury and bacterial invasion, resulting in necrotizing fasciitis. These procedures include surgery for intraperitoneal infections and drainage of ischiorectal and perianal abscesses.
• IM injections and IV infusions may lead to necrotizing fasciitis.
• Minor insect bites may set the stage for necrotizing infections. Streptococci can be introduced into the wounds, but the bacteriologic pattern changes from hypoxia-induced proliferation of anaerobes.
• Local ischemia and hypoxia can occur in patients with systemic illnesses (eg, diabetes).
  • Host defenses can be compromised by underlying systemic diseases favoring the development of these infections. Illnesses such as diabetes or cancer have been described in over 90% of cases of progressive bacterial gangrene.
  • Of patients with necrotizing fasciitis, 20-40% are diabetic. As many as 80% of Fournier gangrene cases occur in people with diabetes.
• In some series, as many as 35% of patients were alcoholics.
• Recent studies have shown a possible relationship between the use of nonsteroidal anti-inflammatory agents (NSAIDs), such as ibuprofen, and the development of necrotizing fasciitis during varicella infections. Additional studies are needed to establish whether ibuprofen use has a causal role in the development of necrotizing fasciitis and its complications during varicella infections. This has not previously been described.

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