gas gangrene

Gas gangrene
Classification and external resources
Photograph before right leg amputation (hemipelvectomy) of a patient with gas gangrene. The right thigh is swollen, edematous and discoloured with necrotic bullae (large blisters). An impressive crepitation is already palpable. At this juncture the patient is in shock.
ICD-10	A48.0
ICD-9	040.0
DiseasesDB	31141
eMedicine	med/843 emerg/211 med/394
MeSH	D005738

Gas gangrene (also known as "Clostridial myonecrosis"^[1]:269) is a bacterial infection that produces gas within tissues in gangrene. It is a deadly form of gangrene usually caused by Clostridium bacteria. It is a medical emergency.

Features

Gas gangrene can cause myonecrosis, gas production, and sepsis. Progression to toxemia and shock is often very rapid.

Pathophysiology

Gas gangrene is caused by exotoxin-producing Clostridial species (most often Clostridium perfringens, and C novyi^[2] but less commonly C. septicum^[3] or C. ramnosum^[4]), which are mostly found in soil but also found as normal gut flora, and other anaerobes (e.g. Bacteroides and anaerobic streptococci). The exotoxin is commonly found in C. perfringens type A strain and is known as alpha toxin. These environmental bacteria may enter the muscle through a wound and go on to proliferate in necrotic tissue and secrete powerful toxins. These toxins destroy nearby tissue, generating gas at the same time.

Other organisms may rarely cause gas gangrene (for example, Klebsiella pneumoniae in the context of diabetes).^[5]

A gas composition of 5.9% hydrogen, 3.4% carbon dioxide, 74.5% nitrogen and 16.1% oxygen was reported in one clinical case.^[6]

Treatment

Treatment is usually debridement and excision with amputation necessary in many cases. Antibiotics alone are not effective because they do not penetrate ischaemic muscles enough to be effective. However, penicillin is given as an adjuvant treatment to surgery. In addition to surgery and antibiotics, hyperbaric oxygen therapy (HBOT) is used and acts to inhibit the growth of and kill the anaerobic C. perfringens.^[7][8]

Additional images

Macroscopic and microscopic findings from a patient who died from intestinal (bowel) gas gangrene.
(a) Macroscopic picture of the edematous intestinal wall with multiple submucosal and subserosal cysts. (b) Histological picture of the intestinal mucosa with non-reactive necrosis. (c) Gram stain of cysts with large rod-shaped bacteria. (d) Electron microscopic picture of a bacterium found in a submucosal cyst.

Hemipelvectomy for gas gangrene.	Muscle biopsy examined under the microscope (haematoxylin-eosin stain, zoom 100×). The large white areas between the muscle fibers are due to gas formation.
Gram stain of a muscle biopsy showing Gram-positive, rod-shaped, anaerobic, spore-forming bacteria in the infected muscle tissue. The result is highly compatible to an infection with Clostridium perfringens.	Gas gangrene of the shoulder.

See also

• Blackleg (disease) (a similar disease in livestock)

References