Gangrene is the medical term for tissue death caused when blood supply to an area of the body is lost because of injury, infection or blood vessel disease. Gangrene is divided into two types, dry and wet. Dry gangrene is caused by blood vessel disease, which typically leads to slowly progressive tissue death. Wet gangrene is a complication of tissue infection wherein extreme tissue swelling chokes off the local blood supply. Gangrene can occur anywhere in the body, although the extremities are particularly vulnerable.
Abnormal Skin Color
With wet gangrene, the skin typically blanches early in the infection. It may also appear mottled with a bluish gray hue. As infection progresses, the skin goes through a series of color changes, from bronze to bluish purple and finally gray-black. Dry gangrene goes through a similar series of skin color changes at a slower pace. The gray-black tissue is dead and begins to shrivel if not surgically removed; this process is called mummification.
Cool Skin Temperature
The skin of an area affected by gangrene is cool or cold to the touch because it is not receiving blood to keep it warm.
Pain, Numbness
In the earliest stage of gangrene, the affected tissues are in critical condition but are not yet dead. Wet gangrene is heralded by the sudden onset of pain that quickly builds in intensity. With its slower course, dry gangrene typically causes a more gradual onset and intensification of pain, which is commonly described as a dull ache. In both wet and dry gangrene, as the tissues and associated nerves are dying, pain turns to numbness and eventually, if left untreated, all feeling in the area is lost because the nerves are dead. It is notable that people with diabetes--a group commonly affected by dry gangrene--may not have pain because of nerve damage from their diabetes.
Marked Swelling
The underlying infection in wet gangrene causes rapid and severe swelling of the affected area, which is often called brawny edema-- swelling that causes the area to be so firm that it feels hard when touched. The affected area often begins to ooze fluid through the skin at this stage. Swelling and fluid drainage are not typical symptoms of dry gangrene.
Blistering
Large blisters called bullae form rapidly with wet gangrene. They are typically filled with dark red fluid, which contains pus and decaying tissue debris. As the blisters break, patches of gangrenous tissue are revealed. An intensely unpleasant smell often emanates from the tissue as it decays and weeps fluid. Gas gangrene--a form of wet gangrene caused by the bacterium Clostridium perfringens--is associated with gas production in the decaying tissues. This may cause a bubbly appearance to the oozing fluid. A crackling sound or sensation may also be noticeable upon touching the affected area. Blistering is not a symptom of dry gangrene.
Fever
Fever is common with wet gangrene, especially if the causative bacteria spreads to the bloodstream--a complication known as sepsis. Fever is uncommon with dry gangrene unless a secondary bacterial infection occurs.
Low Blood Pressure and High Heart Rate
Low blood pressure and high heart rate often occur with wet gangrene. Toxins produced by some causative bacteria can contribute to these symptoms. Sepsis is a common finding when these symptoms are present; shock may develop if the condition is not treated quickly and definitively. Low blood pressure and high heart rate are not common symptoms of dry gangrene.
References
- Mayo Clinic: Gangrene
- Medline Plus: Gangrene
- Merck Manual: Peripheral artery disease
- Patient UK: Gangrene
- "Harrison's Principles of Internal Medicine, 16th Edition"; Dennis L. Kasper, M.D., et al, Editors; 2004
