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Gangrene occurs when there is death and decay of body tissue. It is caused by a lack of blood supply and is most common in the lower limbs, but can occur in the upper limbs and intestine. Lack of blood supply is caused by three major mechanisms: infection, vascular or trauma.
Types of gangrene
There are two broad types:
- Results from diminished blood supply due to vascular problems - eg, peripheral arterial disease (especially consider if cardiac risk factors are present, such as smoking and diabetes mellitus).
- Other causes can be associated with vasculitis - eg, autoimmune conditions such as Raynaud's phenomenon or scleroderma. The area involved will become cold, dry and black and will eventually slough off.
- 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
- Noma is a rapidly progressive opportunistic infection most often affecting the mouth and face that occurs during periods of immune compromise. Noma can also cause tissue damage to the genitals.
- Symmetrical peripheral gangrene occurs in a wide variety of medical conditions and presents as symmetrical gangrene of two or more extremities without large vessel obstruction or vasculitis.
- Fournier's gangrene is a rare but severe necrotising fasciitis of the external genitalia.[3, 4]
- Other forms of necrotising fasciitis.
There are few data, if any, on the prevalence or incidence of gangrene, which may reflect the fact that it occurs with accompanying conditions.
Gangrene can affect any part of the body but most often affects the extremities, ie the fingers and toes. Gangrene can also affect the internal body organs, particularly the gastrointestinal tract.
- Loss of appetite
Symptoms/signs relating to area of involvement
- Erythema in early stages
- Discharge - may be frank pus
- Foul-smelling odour
- The area becomes black
- Erythema may be present
- Coldness and pallor in the affected region
- No discharge
- The affected area may become brown and then black
- Blood tests: FBC, LFTs 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 are 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.
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:
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.
- 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.
- 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).
- 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. Hyperbaric oxygen therapy has been used successfully as adjunctive therapy for wound healing.[6, 7]
- 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.
It is also important to review cardiac risk (if appropriate) and institute risk-reducing measures.
This includes septicaemia, septic shock and loss of the involved area.
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 are associated with a relatively good outcome.
Meticulous attention to care in patients at risk is needed. Thus, people with diabetes 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.
Further reading and references
; Noma and Cervicofacial Necrotizing Fasciitis: Clinicopathological Differentiation and an Illustrative Case Report of Noma. AIDS Res Hum Retroviruses. 2014 Jan 4.
; Symmetrical peripheral gangrene. Trop Doct. 2004 Jan34(1):2-4.
; Fournier's Gangrene Complicating Hematologic Malignancies: a Case Report and Review of Licterature. Mediterr J Hematol Infect Dis. 2013 Nov 15(1):e2013067. doi: 10.4084/MJHID.2013.067. eCollection 2013.
; Fournier's gangrene: our experience with 50 patients and analysis of factors affecting mortality. World J Emerg Surg. 2013 Apr 18(1):13. doi: 10.1186/1749-7922-8-13.
; Necrotizing Soft Tissue Infections: Surgeon's Prospective. Int J Inflam. 20132013:609628. Epub 2013 Dec 24.
; Hyperbaric oxygen and wound healing. Indian J Plast Surg. 2012 May45(2):316-24. doi: 10.4103/0970-0358.101309.
; Hyperbaric oxygen: applications in infectious disease. Emerg Med Clin North Am. 2008 May26(2):571-95, xi.
; Increasing the options for management of large and complex chronic wounds with a scalable, closed-system dressing for maggot therapy. J Burn Care Res. 2012 May-Jun33(3):e169-75. doi: 10.1097/BCR.0b013e318233570d.
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