Gangrene is the medical term for the death of soft tissue as a result of the loss of blood supply to the affected part of the body. The loss of blood supply in turn can result from a disorder of the circulatory system, from trauma, or from infection. Gangrene most commonly involves the fingers, toes, hands, or feet, but can also develop within the internal organs.
There are two major types of gangrene, dry and wet. Dry gangrene is caused by a gradual loss of blood flow through the arteries. It typically develops slowly over a period of years as the person's circulation is impaired by atherosclerosis (hardening of the arteries), diabetes, or long-term smoking.
Wet gangrene develops much more rapidly than dry gangrene. It is caused by an untreated wound infection or by bacteria growing in tissue that has broken down as a result of pressure. Bedsores are a type of wet gangrene that may develop in patients who are bedridden for long periods of time.
Gas gangrene is a deadly subtype of wet gangrene caused by bacteria known as Clostridium perfringens. C. perfringens is an organism that grows in the absence of oxygen. It produces gas as well as toxins; these compounds expand and spread rapidly through nearby tissues. Gas gangrene is a medical emergency.
Dry gangrene typically begins in the parts of the hands and feet that are furthest from the trunk of the body. These are the parts that are most likely to lose their blood supply in patients with diseases that affect the circulatory system. The affected area becomes cold and numb; it begins to turn red as the blood cells inside the smaller vessels begin to break down. It then turns a darker brown or blackish color. The dead tissue may eventually fall off if it is not removed by surgery first.
Wet gangrene develops when the blood flow to the affected body part is blocked—often by a traumatic injury—the blood that collects in the soft tissues supports the rapid growth of bacteria, which causes the tissues to swell and produce a foul-smelling discharge. The affected area is usually discolored and very painful, and the patient typically develops a fever. If the gangrene is not treated, the bacterial infection can spread throughout the body via the bloodstream and kill the patient. The possibility of death from spreading infection is the reason why military surgeons from the time of Augustus Caesar through the end of the nineteenth century routinely amputated the limbs of wounded soldiers; the operations were necessary to give the soldiers a chance to survive injuries to their arms or legs.
Gas gangrene is a type of wet gangrene caused by Clostridium perfringens, a bacterium that grows in the absence of oxygen. In addition to swelling and pain in the affected area, the tissue may also crackle or make a popping sound if the doctor presses on the affected area. The patient
will become very sick very quickly with gas gangrene, often going into shock, sweating heavily, and developing mental symptoms (confusion and disorientation).
Death of a President
On September 5, 1901, President William McKinley (1843–1901) was shot by Leon Czolgosz at a reception at the Pan-American Exposition in Buffalo, New York. Czolgosz fired two bullets into McKinley's abdomen while waiting in line to shake hands with him. One bullet caused only a minor flesh wound, but the other passed completely through his stomach and pancreas and lodged in his back. McKinley was taken to the hospital and appeared to be improving following surgery. The surgeons did not, however, find the bullet as x-ray machines were still experimental in 1901. They closed up the wound with the bullet still inside.
McKinley continued to improve until September 12, when he developed the classic symptoms of gangrene caused by infection: headache, nausea, a rapid but weak pulse. He died two days later and was succeeded as president by Theodore Roosevelt.
A significant consequence of these events was a greater interest in the use of x-rays to detect the location of bullets inside the body. The official report of McKinley's autopsy noted that some organs along the track of the bullet through the president's abdomen had become gangrenous;
gangrene of the pancreas was listed as the cause of McKinley's death. Had modern x-ray equipment been available in 1901, McKinley would have almost certainly survived his wounds.
The frequency of gangrene depends on the type. Gas gangrene is fortunately rare in the United States, with an average of 900 to 1,000 cases reported each year. According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), about 71,000 amputations of the feet and lower legs are performed each year in the United States on diabetics who have developed gangrene. More than 60 percent of all
nontraumatic lower-limb amputations in the United States occur in people with diabetes.
Both wet and dry gangrene affect both sexes and all races equally. Risk factors for gangrene include:
- Old age. The elderly are more likely to develop circulatory disorders leading to gangrene or to be confined to bed and develop bedsores.
- Diabetes. Diabetes tends to weaken the blood vessels over time.
- Diseases of the blood vessels.
- HIV infection.
- Radiation or chemotherapy for cancer.
- Severe injury, including frostbite.
- Long-term smoking. The chemicals in tobacco smoke cause the blood vessels to narrow, reducing the supply of oxygen to body tissues.
The basic cause of gangrene is the loss of blood supply to the soft tissues in a part of the body. This loss may result from circulatory disorders, from traumatic injury, or from infection.
The basic symptoms of wet and dry gangrene have already been described. Gangrene is a serious condition, and anyone with any of the following symptoms should see their doctor at once:
- Pain in the affected area that is out of proportion to the outward appearance of the wound.
- A foul-smelling ooze or discharge leaking from a wound or sore. In gas gangrene, the discharge has a mousy or slightly sweet odor.
- Skin that is colorless, pale, cold, and numb.
- Skin that is turning blue, brown, or black.
The diagnosis of gangrene is based on a combination of the patient's history, a physical examination, a blood test, and imaging studies. The doctor will ask the patient about any recent injuries, exposure to extreme cold, recent surgery, chronic diseases (particularly diabetes), smoking habits, and any disorders that affect the immune system. The physical examination will include examination of the affected body part as well as taking the patient's pulse, temperature, and blood pressure.
Tests and imaging studies that are usually done to evaluate gangrene include.
- Blood test. A higher than normal white blood cell count usually indicates an infection. A blood test may also be done to identify the specific bacterium causing the infection (in wet gangrene).
- X-ray study. This test may be performed to look for gas bubbles in soft tissue when gas gangrene is suspected.
- Computed tomography (CT) scans and magnetic resonance imaging (MRI). These tests may be ordered to check for the spread of gangrene.
- Arteriogram. An arteriogram is a test in which a dye that shows up on an x-ray is injected into the patient's blood circulation. It can help the doctor determine whether any of the patient's arteries are blocked. This type of test is usually done for patients with dry gangrene.
- Removal of a sample of the affected tissue. The sample can be examined under the microscope for signs of tissue death.
- Removal of a sample of fluid from the affected area. The fluid can be cultured in a laboratory to look for signs of C. perfringens when gas gangrene is suspected.
In some cases the patient may be taken directly into surgery to determine how far the gangrene has spread inside the body.
Gangrene is a serious condition requiring treatment in a hospital. A patient diagnosed with dry gangrene will be assessed by a surgeon who specializes in vascular disorders to determine whether it is possible to restore blood flow to the affected area. The tissue that has already died, however, is usually removed surgically.
Wet gangrene requires immediate treatment with intravenous antibiotics to stop the spread of infection and debridement (surgical removal of the dead tissue). If the affected area is large, the patient may need a skin graft to restore the appearance of the limb. In severe cases, the patient's toes, fingers, or limbs may have to be amputated to prevent the spread of infection to vital organs.
Gas gangrene is a medical emergency. The patient is given intravenous antibiotics while the wound is debrided. Following surgery, the
patient may be placed in a hyperbaric oxygen chamber, a room in which pure oxygen under pressure is delivered to the patient. Hyperbaric oxygen raises the oxygen levels in the patient's blood, which in turn may help to fight the bacteria that cause gas gangrene.
The prognosis depends on the type of gangrene, the length of time before the patient sought treatment, and the patient's age, underlying medical conditions, and immune status. Dry gangrene usually has a better prognosis than wet gangrene because it does not involve infection. Gas gangrene has a mortality rate ranging from 25 percent in otherwise healthy patients to 67 percent in patients being treated for cancer.
All people can prevent gangrene by cleansing wounds promptly with an antiseptic; by watching for signs of infection in the wound (pus, redness, swelling, and unusual pain); and by going to the doctor at once if a wound looks infected.
People with diabetes need to take special care to prevent gangrene in the feet, which is a potential complication of the disease. The reason for this complication is that diabetes sometimes affects the nerves in the feet, causing a loss of sensation. The diabetic person may not notice a cut or other injury to the foot because they cannot feel it. An infection can then develop and lead to gangrene. NIDDK recommends that people with diabetes take the following precautions to prevent gangrene in their feet:
- Wash the feet in warm (not hot) water every day and dry them completely, particularly between the toes.
- Check the feet every day for cuts, blisters, swelling, redness, calluses, or toenail problems.
- Cut the toenails once a week after washing the feet.
- Always wear shoes or slippers to protect the feet from injuries.
- Always wear socks or stockings to prevent blisters, even when wearing sandals.
- Wear shoes that fit well, and check them before wearing to make sure there are no rough edges that might injure the feet.
Gangrene will always be a potential complication of traumatic injuries as well as such chronic diseases as diabetes and HIV infection. Recent advances in wilderness and battlefield medicine have reduced the risk of gangrene in injured hikers, explorers, and military personnel. Current clinical trials are evaluating the effectiveness of new antibiotics in treating diabetic foot gangrene and of hyperbaric oxygen therapy in treating gas gangrene.
SEE ALSO Diabetes; Frostbite; Necrotizing fasciitis
WORDS TO KNOW
Amputation: Surgical removal of a limb.
Bedsore: A type of wet gangrene that develops when a bedridden person cannot turn over to relieve pressure on soft tissue caused by the weight of the body. Bedsores are sometimes called pressure ulcers.
Debridement: The medical term for the surgical removal of dead or damaged soft tissue.
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National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Prevent Diabetes Problems: Keep Your Feet and Skin Healthy. Available online at http://diabetes.niddk.nih.gov/dm/pubs/complications_feet/ (accessed August 6, 2008).