When the blood supply to a body part is stopped, the resulting tissue death is called gangrene. There are two major categories of gangrene: dry and wet. The dry type results from cardiovascular disease cutting off circulation, while the wet variety is caused by bacterial infection, often due to injury. Both varieties typically afflict the extremities and require the removal of the dead tissue as the primary medical treatment. Less common subtypes of the disease may destroy parts of the trunk, face, or groin, often after serious trauma or rare medical conditions.
Gangrene is the death of bodily tissues because their blood supply has stopped, depriving them of oxygen. Tissue death — called necrosis — begins if the circulation stops for a sufficiently long time and if enough cells are denied oxygen. Infection, cardiovascular disease, and traumatic injury can all initiate the processes that lead to necrosis. While any body part can become gangrenous, it most commonly afflicts the extremities, particularly hands, feet, and digits. The different varieties of this ailment are classified clinically according to their symptoms and by the disease or injury that started the necrotic process.
One common type of necrosis is dry gangrene. It is frequently the result of arterial blockage due to cardiovascular disease and can arise as a complication of diabetes. This is a slow and progressive illness, not caused by trauma and typically not leading to bacterial infection. Tissues first become red or brownish-black and cold, then dry up, and may fall off the body. If the underlying disease is not treated, dry gangrene may affect more than one body part in a susceptible individual.
Wet gangrene is caused by the infection of a wound, where uncontrolled bacterial cell increases stop blood flow to the affected region. The muscles become invaded with bacterial cells and putrefy, while immune cells are unable to reach the site of infection and kill the bacteria. In gas gangrene, Clostridia bacteria multiply in oxygen-deprived tissue, releasing quantities of gas as a byproduct of their metabolism. Since Clostridia thrive in the absence of oxygen, they increase as the tissue dies.
A rarer type of necrosis that destroys facial tissue is called noma, while necrotizing fasciitis is a more common kind of infection in which bacteria destroy tissues. The dry and wet gangrenes attack any tissues in the bodily region below the point of blood supply blockage, but they especially destroy skeletal muscle. None of the types of gangrene can be treated with antibiotics, since these chemicals cannot reach infected tissues without blood circulating to them. Surgical removal of dead tissue is necessary, and in some cases this involves amputation of a gangrenous limb if necrosis has spread far enough.
