What Is Gangrene?

Wet gangrene of the foot is a medical emergency that needs prompt treatment.

Gangrene is a term that describes dead or dying body tissue(s) that occurs because the local blood supply to the tissue is either lost or is inadequate to keep the tissue alive. Gangrene has been recognized as a localized area of tissue death since ancient times. The Greeks used the term gangraina to describe putrefaction (death) of tissue. Although many laypeople associate the term gangrene with a bacterial infection, the medical use of the term includes any cause that compromises the blood supply (for example, peripheral arterial disease or other blood vessel disease) and results in tissue death in the affected part of the body. Consequently, a person can be diagnosed with gangrene but does not have to be "infected."

There are two major types of gangrene, referred to as dry and wet. Many cases of dry gangrene are not infected. All cases of wet gangrene are considered to be infected, almost always by bacteria. The most common sites for both wet and dry gangrene to occur are the digits (fingers and toes) and other extremities (hands, arms, feet, and legs).

Wet gangrene

Wet gangrene (also termed moist gangrene) is the most dangerous type of gangrene because if it is left untreated, the patient usually develops sepsis and dies within a few hours or days. Wet gangrene results from an untreated (or inadequately treated) infection in the body where the local blood supply has been reduced or stopped by tissue swelling, gas production in tissue, bacterial toxins, or all of these factors in combination. Additionally, conditions that compromise the blood flow such as burns or vascular trauma (for example, a knife wound that cuts off arterial flow) can occur first. Then the locally compromised body part or area becomes infected, which can result in wet gangrene. Wet gangrene is the type that is most commonly thought of when the term gangrene is used. Wet gangrene often produces an oozing fluid or pus, hence the term "wet." Early stages of wet gangrene may include:

• Signs of infection
• Aching pain with swelling
• A reddish skin color or blanched appearance if the area is raised above the level of the heart
• Coolness on the skin surface
• Ulceration
• A crackly sensation when the skin is pressed due to gas in the tissue

These stages may progress rapidly over hours to days.

Dry gangrene

Dry gangrene, if it does not become infected and progress to wet gangrene, usually does not cause sepsis or death. However, it can result in local tissue death with the tissue eventually being sloughed off. Usually, the progression of dry gangrene is much slower (days to months) than wet gangrene because the vascular compromise slowly develops due to the progression of diseases that can result in local arterial blockage over time.

The stages are similar to wet gangrene (see above), except there is no infection, pus, wetness, or crackly-feeling skin because there is no gas production in the uninfected tissue. Disease-fighting cells are not recruited to the area.

There are many diseases that may lead to dry gangrene; the most common are:

• Diabetes
• Arteriosclerosis
• Tobacco addiction (smoking)

Infrequently, dry gangrene can occur quickly, over a few hours to days, when a rapid arterial blockage occurs in part of the body (for example, an arterial blood clot suddenly occludes a small artery to a toe). Dry gangrene often produces cool, dry, and discolored appendages (sometimes termed "mummified") with no oozing fluid or pus, hence the term "dry."

Gangrene is characterized by distinct changes in skin color that occur in stages. Initially, the skin may appear pale due to deprived blood flow to the affected site. As the disease advances, the skin may turn red and then brown. Finally, the skin color may turn greenish-black as the tissue dies and dries up.

Apart from the skin color changes, swelling is commonly observed in the affected area, along with the presence of sores or blisters, indicating tissue damage and potential infection.

The typical features of gangrene may change with different types:

• Dry gangrene: In dry gangrene, the skin gradually becomes dry and black. In the initial stages, a red line may appear around the dying tissue.
• Wet gangrene: In wet gangrene, the affected site typically shows pus, redness, and swelling. Symptoms may include pain, fever, and a crackling sensation when pressing on the area. The skin may appear thin, shiny, and hairless, and it may feel cold and numb.

Additionally, there may be a loss of sensation and tissue sloughing at the affected site.

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 and major risk factors for gangrene are:

• Infections
• Trauma
• Poor wound healing
• Diseases like diabetes mellitus that can affect blood vessels (usually arteries) 

Rarely, Raynaud's disease can lead to gangrene of fingers and toes.

Dry gangrene causes

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 causes

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 or bacterial infection 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 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 the 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 gangrene 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 as described above.
• 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 involving the colon, rectum, or other areas).

Leprosy

Leprosy (Hansen's disease) is not a variant of wet or dry gangrene, although it can result in local tissue loss that can resemble gangrene. It is a disease caused by bacteria that are transferred usually 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 a 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.

Gangrene symptoms 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 symptoms and signs

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 symptoms and signs

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 such as light-headedness due to low blood pressure.

Internal gangrene symptoms

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, apparent symptoms that are characteristic of 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.

A person should suspect gangrene if any local body area changes color (especially if it is red, blue, or black) and becomes numb or painful. If the symptoms include those stated above for either dry or wet gangrene, the individual should immediately seek medical help.

The diagnosis is usually based on the clinical symptoms of either wet or dry gangrene. Often other tests are done in cases of wet gangrene to further define the infecting agent(s), the type of gangrene, and the extent of the infection. For example, X-rays, CT, or MRI studies are done to see how far gas or necrosis (or both) has progressed from the local site. These studies are often done to help determine the extent of gangrene in both limb and internal types of gangrene. Blood cultures as well as cultures of the infected tissue and exudates are usually done to identify the infective agent(s) and to determine appropriate antibiotic therapy.

For dry gangrene, vascular surgeons often do angiography (a radiologic study with dye that shows arterial blood flow in tissues, also termed arteriogram) to see the extent of ongoing or potential arterial blood loss to tissue.

Treatment of gangrene depends upon the type of gangrene (dry vs. wet), the subtype of wet gangrene, and 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 including management of any infections
• Supportive care
• Rehabilitation (occasionally)

Dry gangrene treatment

Dry gangrene is usually treated with surgery 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 in some third-world countries. Many patients, if they do not get infected, can recover from autoamputation.

Wet gangrene treatment

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 need to be administered (usually a combination of two or more broad-spectrum antibiotics, one of which is effective in killing anaerobic bacteria like Clostridium perfringens and another antibiotic effective against methicillin-resistant Staphylococcus aureus or MRSA). Consultation with an infectious disease specialist and a surgeon is recommended.

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 therapy (oxygen therapy 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.

If tissue obtains good oxygenation by adequate arterial blood flow and does not become infected, then both dry and wet gangrene can be prevented. Consequently, avoiding tobacco use and avoiding external trauma like frostbite can help prevent gangrene. Perhaps the best way to prevent gangrene, especially in developed countries, is to keep patients with diabetes under good glucose control and to have them do frequent examinations of their feet for any signs of cuts, infection, or redness. Patients with diabetic neuropathy (for example, numbness in extremity) should do this daily.

If any wound or burn occurs, it should be treated immediately to prevent infection. This is especially important in people with diabetes, vasculitis, or a compromised immune system.

Some patients who notice coolness and redness of a local area (for example, toes, fingers) and get an angiogram that shows arterial blockage can have successful prevention of dry gangrene (and possibly wet gangrene). However, this needs to occur quickly so the vascular surgeon can remove the clot or obstruction in the artery before local tissue dies.

Patients with dry gangrene usually do well as long as they do not become infected. These patients lose some local function due to tissue loss and, if they have an ongoing disease like diabetes, may develop dry gangrene again. In general, patients recover with minimal residual problems if the tissue loss is small.

Patients with wet gangrene usually have a poorer prognosis than those with dry gangrene. Statistics for the U.S. suggest that the mortality (death) rate is low in patients hospitalized with gangrene. The mortality (death rate) increases if the patient becomes septic. If treatment is initiated early, some patients need some form of amputation (digits, limbs). Although the death rate has remained steady, the number of cases of gangrene has been increasing in the United States in recent years, possibly due to the increasing numbers of patients with diabetes and other diseases that affect the vascular system, but these data are not complete.

• How does gangrene start? Gangrene starts when the blood supply to a tissue is interrupted, resulting in tissue death. Blood supply to the tissue can be obstructed for various reasons, such as injury, infection, chronic diseases, medications, blood vessel disease, and a suppressed immune system.
• Can gangrene be cured? Gangrene can be cured if detected in the early stages. Treatment for all types of gangrene involves the removal of dead tissue, preventing the spread of infection, and treating the underlying cause. The recovery rate for gangrene is higher if detected and treated in the early stages.
• What are the three symptoms of gangrene? The three major symptoms of gangrene include skin discoloration, swelling, and severe pain at the affected site. Other symptoms include foul-smelling discharge, cold and numb skin, and fever.
• How to prevent gangrene. The best ways to prevent gangrene include controlling your diabetes or other chronic conditions, taking care of wounds, avoiding tobacco, maintaining a healthy weight, and avoiding frostbite by staying warm.
• How do you detect gangrene? Gangrene can be detected using a combination of physical examination, blood tests, and imaging tests. To identify the cause of infectious gangrene, cultures may be obtained to detect the specific bacteria involved. The physician may also perform surgery to check if the gangrene has spread.