Gangrene is the death of tissue due to an interruption of blood flow to that particular area of the body. The condition primarily affects the extremities with the toes being more susceptible than the fingers. It is important to note that you can also have tissue death of the muscles and internal organs as well, but this discussion will be directed toward the toes and feet.
Causes of gangrene include the following:
One of the protocols in foot surgery is to always make sure there is enough distance between two incisions so that the skin in between does not have its circulation cut off and thus die.
Dry gangrene is characterized by dry leathery type skin which is usually purplish to black in color. It is seen more in people who have hardening of the arteries. Generally, this type is not infected. In the picture below you can see the distinct demarcation of healthy vs. unhealthy tissue on the great toe. This black area is completely dry and has a leathery texture to it.
Wet Gangrene means that there is a bacterial infection. It is characterized by swelling, drainage, and possible blistering. This is considered a medical emergency and needs to be treated immediately because these infections can spread rapidly. Looking at the picture to the right you will see that it looks similar to the above picture, but it is not. This toe is actively draining exudate (pus) and there is an opening in the toe leading to deeper tissue.
Gas gangrene affects deep muscle tissue that has been deprived of its blood supply either by surgery or trauma. This will occur more in the foot rather than the toes. When the blood supply is cut off to a muscle, a bacteria, Clostridium perfringens, produces a toxin which creates gas under the skin. This will eventually cause tissue death. This is also considered a medical emergency as these infections can also spread very quickly. If you look at the xray below, note the yellow arrow. It is pointing to a cloudy area in the xray which is the gas that is produced from the infection.
As just stated, wet and gas variety are medical emergencies and require immediate care. The dry version also requires medical attention but is usually not an acute emergency but can certainly worsen if not properly treated. In many cases of dry gangrene, particularly in parts of the world not readily accessible to medical care, the dead tissue may just slough off (autoamputation). If the patient is lucky and the area does not get infected the area may heal on its own.
The other two types of gangrene are treated much more aggressively. Untreated gangrene of the wet and gas variety will lead to a worsening of the associated sepsis which can lead to death.
Usually there will be a surgical procedure to remove the "dead" tissue. The surgeon will need to determine the demarcation between where there is no circulation and adequate circulation and the removal of tissue will take place at that junction. If gangrene of a toe is just a symptom of very poor circulation in the leg such as in a diabetic, then an amputation further up the foot or leg may be necessary.
In addition intravenous antibiotics will be administered to clear up any infection. This will all require a hospital stay. Some institutions have begun treating this condition with hyperbaric oxygen which is high pressure oxygen that is delivered to an oxygen deprived area (such as the foot with poor circulation) in an effort to re-introduce oxygen into the tissues that are otherwise not getting enough oxygen due to poor circulation. The idea here is two-fold. One is to give the tissue the oxygen it needs to heal itself and the other is to kill some bacteria known as anaerobic bacteria which thrive in an environment where there is low oxygen tension.
Like most medical conditions, the best way to treat this condition is through prevention.
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