Foot Gangrene in Diabetes

Gangrene is a consequence of localised tissue necrosis or tissue death, often due to compromised blood circulation to the affected tissue. Three main types of lower extremity gangrene are seen in patients with diabetes—dry, wet and gas gangrene. Dry gangrene is consequent on ischaemia, wet gangrene has associated infection and oedema on the backdrop of ischaemia, and gas gangrene is myonecrosis from bacterial exotoxins, classically from Clostridium species. Prevalence rates of gangrene vary from 4.1 to 41.4%, with a male-female ratio of 3:1. Dry gangrene manifests as an area of black, dry, shrunken tissue that is well-delineated from the surrounding area, wet gangrene shows associated oedema, oozing and sometimes has malodour, and there is less delineation, while with gas gangrene there is a then blue-black discolouration of the skin, with associated bullae and systemic symptoms such as high fever. Pathology shows coagulative necrosis in dry gangrene and liquefactive necrosis in wet, with myonecrosis and presence of bacteria in clostridial gas gangrene. Therapy depends on the clinical scenario. It may be general, medical and surgical and include smoking cessation, exercise, antibiotics, vasoactive agents to improve circulation, hyperbaric oxygen therapy and revascularisation procedures.