Written by Dr. D. Rao
This is the bluish-purple or purplish-red discolouration which appears under the skin in the most superficial layers of the dermis [rete mucosum] of the dependent parts of the body after death, due to capillo-venous distention. It is also called post-mortem staining, subcutaneous hypostasis, livor mortis, cadaveric lividity, suggillations, vibices and darkening of death. the intensity of the colour depends upon the amount of reduced haemoglobin in the blood. In cases of large amount of reduced haemoglobin before death, the blood has deep purplish-red colour. It is caused by the stoppage of circulation, the stagnation of blood in blood vessels, and its tendency to sink by force of gravity. The blood tends to accumulate in the small vessels of the dependent parts of the body. Filling of these vessels produces a bluish-purple colour to the adjacent skin. The upper portions of the body drained of blood are pale. The colour of the hypostasis may vary from area to area in the same body.
The distribution of the stain depends on the position of the body. In a body lying on its back, it first appears in the neck, and then spreads over the entire back with the exception of the parts directly pressed on, i.e. occipital scalp, calves and heels. Any pressure prevents the capillaries from filling, such as the collar band, waist band, belts, wrinkles in the clothes, etc. and such areas remain free from colour and are seen as strips or bands called vibices. Such pale areas should not be mistaken for marks due to beating, or when they are present on the neck, due to strangling. Hypostasis is usually well-marked in the lobes of the ears and in the tissues under nails of the fingers. As the vessel walls become permeable due to decomposition, blood leaks through them and stains the tissues. At this stage, hypostasis does not disappear, if finger is firmly pressed against the skin. the pattern of lividity may be modified by local changes in the position of the body, e.g., if the head is turned to one side and slightly flexed on the neck for some hours after death blood may gravitate into a linear distribution determined by the folds formed in the skin and subcutaneous tissues. If such a body is examined after the neck has been straightened, the linear discolouration of the stains may be mistaken for marks due to beating. If the body is lying in prone position, the lividity appears in the loose connective tissues in front, the colour is intense and Tardieu spots are common. Sometimes, the congestion is so great that minute blood vessels are ruptured in the nose, and cause bleeding. If the body has been lying on one side, the blood will settle on that side, and if lying on back the staining will be seen on the back. Sometimes, blotchy areas of lividity appear on the upper surface of the limbs due to some irregularity of capillary dilatation at the time of death. if the body has been suspended in the vertical position as in hanging, hypostasis will be most marked in the legs, and hands, and if suspension be prolonged for a few hours, petechial haemorrhages are seen in the skin. in drowning, post-mortem staining is usually found on the face, the upper part of chest, hands, lower arms, feet and the calves, as they are the dependent parts, if the body is constantly moving its position, as after drowning in moving water, the staining may not develop. If the body is moved before the blood coagulates, these patches will disappear and new ones will form on dependent parts, but lividity to a lighter degree remains in the original area, due to staining of the tissues by haemolysis. When coagulation in capillaries takes place, the stains become permanent and this is known as fixation of post-mortem staining. This usually occurs in about six hours, but the condition of blood at the time of death exerts a considerable influence. Persistent fluidity of the blood appears to be due to presence of fibrinolysins. Hypostases may resemble bruises. In doubtful cases, a portion should be removed for microscopic examination.
Petechiae or larger haemorrhages and palpable blood blisters may develop in areas of hypostasis commonly in the back of the shoulders and neck, and sometimes on the front of the chest, even when the body is lying on its back. They are common in cyanotic congestive types of death, and appear more prominent with the increase in post-mortem interval, and may blacken the face and skin. They are more prominent when the body lies with the head downwards.
In a dead body lying on its back, blood accumulates in the posterior part of the scalp due to gravity. In advanced decomposition, due to lysis of red cells and breakdown of the vessels, blood seeps into the soft tissues of the scalp. This appears as a confluent bruising and cannot always be differentiated from true ante-mortem bruising.
The hypostatic areas have distinct colour in certain cases of poisoning, e.g.
Hypostasis also occurs in the internal organs and the dependent parts of the liver, spleen, kidneys, larynx, lungs, heart, intestines and brain show colour changes similar to that in the skin. Hypostasis in the heart can simulate myocardial infarction, and in the lungs it may suggest pneumonia; dependent coils of intestine appear strangulated.
Changes in postmortem:
Lividity occur when putrefaction sets in. in early stages, there is haemolysis of blood and diffusion of blood pigment into the surrounding tissues, where it may undergo secondary changes, e.g., sulphhaemoglobin formation. The capillary endothelium and the surrounding cells show lytic changes. Microscopically, the cellular outlines are obscured and the capillaries are not factive changes and it becomes impossible to determine whether the pigment in a stained putrefied area originated from an intravascular [hypostasis] or/and intravascular localized collection of blood [contusion]. There is diffusion of blood-stained fluid in the chest or abdominal cavities. As decomposition progresses, the lividity becomes dusky in colour and turns brown and green before finally disappearing with destruction of the blood. In mummification, lividity may turn from brown to black with drying of the body.