Gangrene can be subdivided into two types: With or without bacterial infection. Gangrene without bacterial infection can occur in relation to diseases or damages with a poor blood circulation. A slow disruption of the supply of blood and oxygen to the tissue causes the area to dry up. This type is called dry gangrene. The suffering will not spread to the surrounding tissue but in more rare cases, it can develop into wet gangrene.
If the gangrene has formed wounds, the wounds will be in danger of being infected with bacteria. Most likely to infect such wounds are the most common bacteria present on our skin and mucous membranes. They dissolve the tissue and make the wound rot and form a greenish-black substance with an awful smell. This is very painful. Once the pain stops it is caused by the gangrene being very progressed. This type of gangrene is also called wet gangrene.
The worst form of gangrene is called gas gangrene. This type can develop in relation to tissue damage with large, open wounds contaminated with soil. In soil is a bacteria with the name of Clostridium perfringens. It propagates quickly in damaged tissue with a low content of oxygen. It produces tissue-damaging enzymes and toxins which liberate a malodorous gas and kill the surrounding healthy cells making the infection spread. If you touch this infected tissue filled with gas, you will hear a characteristic crepitation. The bacteria also liberate a toxin which kills the cells located around the affected area making way for spreading of both the infection and the damage. The toxin can then pass into the bloodstream and cause a serious poisoning there.
Gangrene can arise in the skin and subcutis, in fingers, feet, toes, lower legs, and even in bones, muscles, and tendons. In more rare cases, gangrene can occur in the whole leg if the circulation of blood is terminated. Gangrene can also occur in a piece of the intestine if a blood vessel is blocked or compressed. Burns and contusion can also cause tissue death. In severe cases fever can arise.
Quite some time will pass before gangrene occurs in a finger, for example. First the finger will swell and become red and very sore. Then, about an hour or two will pass from the time the flow of blood has totally stopped until the cells have become so damaged that they cannot be saved. If this happens, an amputation is requried because toxins will form in the dying part of the body which will otherwise damage the rest of the body.
This type of gangrene can for example be caused by dressings that are too tight or children playing with rubber bands. If a part of the body - e.g. a finger - is prevented from circulating blood, the cells will not receive oxygen and nutrients and they will neither be able to get rid of their waste products. As time goes by, the cells will suffocate because they will not get the required oxygen and because they will "drown" in their own waste products.
Most cases of gangrene occur in very cold areas such as Greenland, Siberia, Alaska, the northern part of Norway and Sweden and even further north. Especially the distal extremities are in danger because that is where the effect of the cold is largest. If an external organ like the ear becomes very cold and approaches the freezing point, the water inside the cells of the ear will begin to freeze. This makes the water expand and threatens to blow the cells and thereby kill them.
Another re-ocurring cause of gangrene is circulatory diseases in which the blood supply is reduced or disrupted to some part of the body, plus cardiovascular diseases such as blood clots and atherosclerosis. When gangrene occurs in connection with other diseases - e.g. longterm diabetes - the cause is the other disease having either destroyed the blood vessels in that part of the body or having calcified the vessels to such an extent that the blood can no longer flow through them. The same effect is produced as that of a rubber band being put around a finger and subsequently the cells will die in the area that the blood cannot reach.
Under dirty conditions, many bacteria often occur. The risk of wet gangrene is particularly large in wounds that have occured in e.g. traffic accidents and have not been cleaned properly. To prevent wet gangrene from spreading, an airtight container is often placed around the affected body area. Oxygen is then pumped into the container with overpressure and in this way the growth of the putrefactive bacteria is inhibited because they cannot thrive in an environment that is rich in oxygen.