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Necrosis
Last reviewed: 23.04.2024
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[What causes necrosis?
Necrosis is caused by causes that are conditionally divided into endogenous and exogenous. Exogenous factors are: mechanical trauma, exposure to extreme temperatures, electric current, ionizing radiation, acids, alkalis, heavy metal salts, certain microorganisms, for example necrobacteria, anthrax, putrefactive microflora.
Endogenous factors are diverse, they are divided into: vascular, neurohumoral, allergic and metabolic.
Necrosis has 3 stages of development: prenecrosis (condition of the organ or tissue before irreversible changes occur); death (irreversible cessation of life); destructive changes (decay, removal, delimitation of residues).
Clinical and anatomical forms: coagulation (dry) necrosis, colliquated necrosis (moist, gangrene, infarction).
Mechanical and thermal injuries cause, for the most part, the development of local processes and local necrosis, without causing a general reaction of the body. Although their prevalence can be from small areas to fairly large, for example, with burns; as well as the depth of tissue damage.
Dry necrosis is characterized by rapid coagulation of tissues with the formation of a dense scab of brown or black; around it, edema and hyperemia rapidly decline and a clear demarcation line forms separating necrosis from healthy tissues. In the subsequent there is its slow rejection with the replacement of scar tissue or ulcer is formed. To dry necrosis can be attached to the infection, in which case it turns into a wet one.
Wet necrosis develops in the presence of infection or when they form in a moist environment, for example, in wounds, burns. This necrosis is characterized by the formation of a loose, intimately cohesive with the tissues of a scab of white or dirty-gray color; The demarcation line is weakly expressed; The tissues around the scapula are swollen and hyperemic; there is a general reaction of the body.
In cases where necrosis affects the entire limb or part of it (for example, the foot when frostbite), and also the organ or part of it, the pathology is defined by the term "gangrene", for example: gangrene of the foot, limb, lung, gut, gangrenous cholecystitis, gangrenous appendicitis and etc. The basis of gangrene are vascular disorders, primarily arterial. With a rapid violation of blood circulation, necrosis proceeds almost instantaneously. This happens with thrombosis of the arteries (rarely veins, for example, thrombosis of mesentery vessels), when exposed to microflora, for example, anaerobic. In the case of a slow development of circulatory disorders: obliterans. Atherosclerosis, endarteritis, Raynaud's disease, diabetes mellitus, etc., the prenecrotic phase is prolonged, is accompanied first by tissue atrophy, and then by the development of gangrene in case of decompensated blood flow. One of the forms of gangrene of the skin and subcutaneous tissue are bedsores that arise because of prolonged compression of tissues in the forced position and disturbance of microcirculation in them. Especially often the formation of decubitus, and extensive, occurs when the spinal cord is affected (Bastian's law), in other cases necrosis is local, and may be multiple, in the areas of the greatest compression of the skin. Gangrene in the clinical course is divided into dry and wet.
Dry gangrene, as a rule, is superficial or engages small distal segments of the limb segment, for example, one or more fingers. They have a brown or black color, the demarcation line is well defined, surrounding tissues, although atrophic, but have no signs of inflammation. There is no general reaction of the body to the process, only manifestations of the underlying and accompanying diseases.
Wet gangrene of extremities and internal organs are accompanied by rapid spread of edema and hyperemia, involvement in the lymphatic system, rapid destruction of tissues, increasing general intoxication of the body. Dry necrosis can persist, but around it develops edema and hyperemia of tissues.