How Is Gangrene Diagnosed?
Gangrene is a progression to a climax in an incessant infectious process. The diagnosis is typically obvious by inspection and it is based on the type of tissue infected:
- Necrotizing cellulitis (soft tissue–fat, skin)
- Necrotizing fasciitis (fascia–deep soft tissues)
- Necrotizing myositis (muscle)
These different three layers exist in tissue planes which offer paths for the rapid spread of the infection, which is the cause of it often getting out of control even to the point of death.
Soft Tissue Gangrene
Necrotizing cellulitis is usually caused by Clostridium species or a mix of several bacteria. This does not extend deeper to the fascia or deep muscles, so although there is usually crepitus, there usually is not severe pain or swelling.
Necrotizing fasciitis is infection of the deeper tissues such as the fascia–the tough, fibrous tissue that overlies muscle. This layer is a poorly vascularized layer which lacks the full complement of immune defenses. This disadvantage, along with its extensive tissue expanse that facilitates spread, makes it particularly difficult to treat. The usual infectious organism is an anaerobic bacterium alone or in combination with other anaerobes.
Streptococcus aureus may be the infectious agent, whose exotoxins can produce toxic shock syndrome, shock, organ failure, and death.
Gangrenous involvement of the muscle is usually due to group A Streptococcus or other resistant Streptococci. When the organism is Clostridium, this can be the very destructive and virulent Clostridial myonecrosis (also called “gas gangrene”).