Gangrene is death of body tissue due to lack of blood flow or infection. Learn about the types, causes, risk factors, complications and prevention of gangrene, and when to seek emergency treatment. Wet, or infected, gangrene is characterized by thriving bacteria and has a poor prognosis (compared to dry gangrene) due to sepsis resulting from the free communication between infected fluid and circulatory fluid. 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. Written by a GP. Gangrene is when lack of blood flow causes tissues in your body to die. It can be dry, wet, gas, Fournier’s or internal gangrene. Learn about the types, symptoms, causes, complications and treatments of gangrene.