Gangrene is a medical term used to describe the death of an area of the body. It develops when the blood supply is cut off to the affected part as a result of various processes, such as infection, vascular (pertaining to blood vessels) disease, or trauma. Gangrene can involve any part of the body; the most common sites include the toes, fingers, feet and hands.
Two major types of gangrene exist:
- Dry gangrene is caused by a reduction of blood flow through the arteries. It appears gradually and progresses slowly. In most people, the affected part does not become infected. In this type of gangrene, the tissue becomes cold and black, begins to dry, and eventually sloughs off. Dry gangrene is commonly seen in people with blockage of arteries (arteriosclerosis) resulting from increased cholesterol levels, diabetes, cigarette smoking, genetic and other factors.
- Wet or moist gangrene develops as a complication of an untreated infected wound. Swelling resulting from the bacterial infection causes a sudden stoppage of blood flow. Cessation of blood flow facilitates invasion of the muscles by the bacteria and multiplication of the bacteria because disease-fighting cells (white blood cells) can not reach the affected part.
- Gas gangrene is a type of wet gangrene caused by the bacteria known as Clostridia. Clostridia are a type of infection-causing bacteria that grow only in the absence of oxygen. As Clostridia grow, they produce poisonous toxins and gas; therefore, the condition is called gas gangrene.
The symptoms of gangrene vary according to the type of gangrene (wet or dry), the anatomic location (external versus internal sites), and which organ system(s) are affected.
Dry gangrene often begins with the affected area first becoming numb and cool. Discomfort levels vary with the patient's perception. The local area (for example, toe or finger) then starts to discolor, usually turning from reddish to brown and eventually black. During this time, the local area shrinks, becomes dry (mummified), and may slough off the body. Dry gangrene caused by immediate loss of arterial blood supply can first turn pale or bluish and then progress as above.
Wet gangrene, in contrast to dry gangrene, usually begins with swelling and a very painful affected area that may be initially red and show signs of decay (sloughing tissue, pus, local oozing of fluid). Often the fluid and the affected area develop a very bad smell, due to the presence of such foul-smelling compounds as cadaverine and putrescine, which are produced as the infectious agent(s) destroy tissue. This dead and dying tissue develops a moist and black appearance. Additional symptoms that are often seen in patients with wet gangrene are fever and other signs of sepsis.
Internal gangrene, a variant of wet gangrene, has less obvious initial symptoms because the wet gangrene occurs in the internal organs. The patient may be very ill (septic) with gangrene but show few if any visual symptoms that are characteristic for wet gangrene. Occasionally, the skin overlying an organ with wet gangrene may become reddish or discolored, and the area may become swollen and painful.
When the surgeon exposes the infected organ, the signs of wet gangrene are apparent. The symptoms vary somewhat according to the organ system infected; for example, patients with gangrene of the bowel due to an incarcerated hernia can have severe pain at the site of the hernia while a gangrenous gallbladder can result in severe pain located in the upper right side of the abdomen.
The common cause of either wet or dry gangrene is loss of an effective local blood supply to any tissue. Loss of the blood supply means tissues are deprived of oxygen, thus causing the cells in the tissue to die. The most common causes of tissue blood supply loss are infections, trauma and diseases that can affect blood vessels (usually arteries).
Dry gangrene can result from any of a number of diseases or mechanisms that can reduce or block arterial blood flow. Although the most common diseases that can cause dry gangrene are diabetes, arteriosclerosis, and tobacco addiction, there are many other lesser-known diseases that can lead to this problem.
For example, some autoimmune diseases that attack blood vessels (vasculitis syndromes) may result in enough damage to cause dry gangrene. In other cases, dry gangrene can result from various external mechanisms such as burns, frostbite, and arterial trauma caused by accidents, wounds, or surgery.
Wet gangrene can result from all the causes listed above for dry gangrene but always includes infection. In some cases of wet gangrene, the initial cause is considered to be the infection. Although many types of organisms (mainly bacteria) are known to participate in wet gangrene infections, the classic bacterial organism associated with wet gangrene is Clostridium perfringens, an anaerobic bacterium that grows best when oxygen is not present.
These bacteria can cause myonecrosis (muscle fiber death) with its exotoxins and produce gas bubbles in the dead and dying tissues (gas gangrene).
This leads to localized swelling with compression and loss of blood flow to tissue, allowing bacteria to extend the infection to the connective tissue of muscle, skin, and other areas, causing necrotizing fasciitis (death of connective tissue). Necrotizing fasciitis, in turn, allows the infection to spread, frequently with speed, out of the locally infected site to adjacent areas or to the bloodstream (sepsis).
Although this cascade of events is seen with Clostridium perfringens often as the single infecting organism type, it can be caused by many other organisms such as Streptococcus, Staphylococcus, Bacteroides, and Escherichia. Usually two or more of these organisms occur in the infection, and many investigators suggest that together the organisms help each other (synergy) to extend the infection.
There are several subtypes of wet gangrene:
- Gas gangrene means gas is present in the gangrenous tissue.
- Fournier's gangrene is gangrene with necrotizing fasciitis that occurs mainly in male genitalia.
- Internal gangrene is a general term that means gangrene is affecting an internal organ. Internal gangrene types are usually named after the organ that is affected (for example, gangrene of the appendix, gangrenous gallbladder, and gangrenous bowel).
Leprosy (Hansen's disease) is not a variant of wet or dry gangrene, although it can result in local tissue loss. It is a disease caused by Mycobacterium leprae that is transferred from person to person.
It causes nodules and sores. M. leprae infection slowly destroys peripheral nerve endings in digits and mucous membranes over a period of years with loss of sensation. Digits and other local areas get repeatedly injured due to sensation loss and can become mutilated or develop atrophy and be sloughed off. However, if the chronic lesions become infected with other organisms, wet gangrene can develop in patients with leprosy.
Treatment of gangrene depends upon the type of gangrene (dry vs. wet), the subtype of wet gangrene, and upon how much tissue is compromised by the gangrene. Immediate treatment is needed in all cases of wet gangrene and in some cases of dry gangrene. Treatment for all cases of gangrene usually involves surgery, medical treatment, supportive care, and occasionally, rehabilitation therapy.
Dry gangrene is usually treated by a surgeon that removes the dead tissue(s), such as a toe. How much tissue is removed may depend on how much arterial blood flow is still reaching other tissue(s). Often, the patient is treated with antibiotics to prevent infection of remaining viable tissue. The patient may also receive anticoagulants to reduce blood clotting. Supportive care can consist of surgical wound care and rehabilitation for reuse of the digits or limb.
Some patients simply slough off the dry gangrenous tissue (termed autoamputation). This happens most often when medical and surgical caregivers are not readily available to the patient in remote areas or some Third World countries. Many patients, if they do not get infected, can recover from autoamputation.
Wet gangrene is a medical emergency and needs immediate treatment. Treatment is usually done in a hospital, and a surgeon needs to be involved because the local area needs debridement (surgical removal of the dead and dying tissue). In some patients, debridement will not be adequate therapy, and amputation of a limb may be needed.
At the same time as surgical treatment, intravenous antibiotics (usually a combination of two or more antibiotics, one of which is effective in killing anaerobic bacteria like Clostridium perfringens and another antibiotic effective against methicillin-resistant Staphylococcus aureus or MRSA) need to be administered. Internal gangrene requires an operation in the hospital to remove the gangrenous tissue.
Some patients develop sepsis and require the support of an intensive-care unit in which supportive care for other life-threatening problems such as hypotension (low blood pressure) can be treated. Rehabilitation therapy for patients with amputation is highly recommended.
Some clinicians treat gangrene, especially wet gangrene, with hyperbaric oxygen (oxygen given under pressure with the patient inside a chamber). Since some studies indicate that hyperbaric oxygen treatment improves tissue oxygen supply and can inhibit or kill anaerobic bacteria, this therapy is used to treat patients with gangrene.
However, it is not available in many hospitals and is used in conjunction with the above described therapeutic methods, not as a primary therapy for wet gangrene.