Types of gangrene

There are two broad types:

• Dry gangrene: results from diminished blood supply due to vascular problems, eg arteriosclerosis or atherosclerosis (especially consider if cardiac risk factors are present, such as smoking and diabetes mellitus (DM)). Other causes can be autoimmune, eg Raynaud's disease or scleroderma. The area involved will become cold, dry and black and will eventually slough off (essentially, mummification of the area).^[1]
• Wet gangrene: usually follows infection in the tissues with organisms including streptococci and staphylococci. The swelling resulting from the infection and consequent inflammation leads to blockage of the blood vessels supplying the area in question. As infection is associated with release of discharge, it has been termed "wet". Gas gangrene is a particular subtype of wet gangrene and is discussed in the separate article Gas Gangrene.

Other specific types of gangrene

• Gas gangrene
• Noma - gangrene which involves the face
• Fournier's gangrene - gangrene of the genitalia
• Necrotising fasciitis

Epidemiology

There are few data, if any, on the prevalence or incidence of gangrene, which may reflect the fact that it occurs with accompanying conditions.

Presentation

• Fever
• Loss of appetite
• Tachycardia
• Hypotension
• Tachypnoea

Symptoms/signs relating to area of involvement:

Wet gangrene:

• Swelling
• Erythema in early stages
• Pain
• Discharge - may be frank pus
• Foul-smelling odour
• Area becomes black

Dry gangrene:

• Erythema may be present
• Coldness and pallor in the affected region
• Numbness
• No discharge
• Affected area may become brown and then black

Investigations

• Blood tests: full blood count, liver function tests and renal function. Clotting screen and fibrinogen may be required in more severely ill patients. Blood glucose should also be measured.
• Microbiology samples: these may include swabs of the infected area in wet gangrene and also peripheral blood cultures (multiple samples preferable).
• Imaging: local radiographs of the affected area may help detect the presence of gas, as seen in gas gangrene. CT or MRI scans may also be performed to determine the extent of involvement of the local area (especially if surgery is being considered).
• Specific tests: these are usually aimed at investigating the underlying cause. For example, an arteriogram is likely in dry gangrene.

Associated diseases

There are underlying diseases which can be associated with gangrene, and which should be looked for, especially if the cause of gangrene is unclear. They include:

• Atherosclerosis
• DM
• Raynauds disease
• Peripheral vascular disease

Management

This initially involves resuscitation with attention to airways, breathing and circulation. Once patients are stable they need to receive therapy for the gangrene which can involve the use of antibiotics and surgical debridement. It is important to note that antibiotics may not penetrate the tissue involved but will help prevent spread of infection.

Wet gangrene:

• Analgesia
• Broad spectrum intravenous antibiotics, eg antipseudomonal penicillin, metronidazole and possibly aminoglycosides (check with local microbiologist)
• Surgical debridement
• Amputation may be required if wet gangrene cannot be controlled

Dry gangrene:

• Requires restoration of blood supply to the gangrenous area
• Amputation may be required if blood supply cannot be restored (although, if a small area is involved, auto-amputation may take place)

Other therapies:

• Hyperbaric oxygen therapy - this provides the patient with higher than normal levels of oxygen which will then pass to the gangrenous area and lead to faster wound healing. The downside is that this treatment requires patients to lie in a chamber which may be claustrophobic and it is not readily available at present.^[2][3][4]
• Maggot therapy - specially bred from sterile eggs, maggots can be applied under gauze for a few days, leading to tissue debridement. They also release antibacterial agents.^[2][5]

It is also important to review cardiac risk (if appropriate) and institute risk-reducing measures.

Complications

This includes septic shock and loss of the involved area.

Prognosis

Prognosis depends on the presence of other morbidity, the area of the body affected and the extent of gangrene. One quarter of patients will develop septic shock which has a high fatality rate. Early recognition and institution of treatment is associated with a good outcome.

Prevention

Meticulous attention to care in patients at risk is needed. Thus, diabetic patients and those known to have peripheral vascular disease must be educated on watching for signs of infection and/or dry gangrene. These patients also need education about proper foot care.