(Synonyms — post mortem hypostasis, postmortem lividity, livor mortis, vivices, suggilation, postmortem staining).
It is another early change of the body after death. It is the discolouration that occurs due to settling of blood after death.
Definition — It is bluish or reddish-purple discolouration due to capillo-venous distention with blood, at the undersurface of skin of the dependant parts of the body, due to settling of the blood in those areas due to the pull of the gravity, when circulation to keep the blood in motion ceases.
In some specific circumstances the colour of the postmortem staining may vary, which has been discussed under the heading medicolegal importances.
Formation of the postmortem staining
When the body is left undisturbed without change of its position, the staining starts appearing in small patches at the dependant parts of the body, by the end of the first hour after death. In a body, which lies in supine position the stained patches first appear over the back of the shoulders and posterior aspects of the flanks of the abdomen, Gradually the small patches increase in size and coalesce with each other to form uniformly stained large areas on the back of the trunk and also on the back of the limbs, if the body is in supine position. For completion of the spreading of the postmortem staining, it takes about 5-6 hours. After formation, the staining gets fixed over the areas.
Fixation of the postmortem staining — After complete formation of the postmortem staining, if the body is still left undisturbed for a period of another 5-6 hours then, the staining over the areas gets fixed. If the position of the body is disturbed or altered after fixation of the staining then, the staining will not be disturbed and will remain more or less as such, though the colour may slightly fade in intensity. After fixation of the staining, if the position of the body is reversed then, there will not be any remarkable resettling of the blood in the newly assumed dependant parts. However mild degree resettling of the blood with appearance of faint postmortem staining over the new dependant parts, is not impossible. But, if the position of the body is reversed after formation of the staining but before its fixation, then there may be total resettling of the blood with formation of postmortem staining at the undersurface of the newly assumed dependant parts of the body.
Fixation of the postmortem staining, was for a long period, thought to be due to intravascular coagulation of the settled blood. But in practice, very little clotting of the blood is seen in the small veins and capillaries, during post mortem examination. During dissection of the body, though passive, there is free oozing of blood from the margins of the dissection or incision. However, postmortem clots may be present in the large vessels and in the chambers of the heart. This sufficiently indicates that, though postmortem clotting of blood occurs, it does not remain clotted in the smaller vessels. This is due to liquefaction of the postmortem dots in the smaller vessels and capillaries due to the action of fibrinolysin, liberated from the vascular endothelium at the time of death as a part of the death reaction. Actually, fixation of postmortem staining occurs mainly due to certain physical factors . Firstly, after the formation of the postmortem staining blood cannot easily pass through out of the capillaries due to the capillary action. Secondly, by the time there has been total settling of the blood, rigor ( mortis is well established all around the body. This change in the muscles obliterates the big vessels passing through them. Hence, after this period, the blood cannot pass through these vessels to settle in the small venules and capillaries in a new area. Thirdly, after the full establishment of rigor mortis the venules etc. lie almost empty and compressed in the rigid muscles at that time and cannot be easily distended by the resettling blood.
Some specific phenomena related to the post mortem staining —
1. As postmortem staining occurs externally on the dependant parts of the body, it also occurs at the dependant parts of all the internal organs, the blood of these organs settling at their dependant parts.
2. The staining becomes discoloured and the area of distribution gets disturbed, once decomposition starts in the body.
3. Postmortem staining is an intra-vascular phenomenon and there is no extravasation of blood in the area.
4. The areas of the dependant parts which remain in direct contact with the ground or the bed, do not show any staining and appear rather pale than what these areas were during life. This phenomenon is known as CONTACT PALOR. This occurs due to the fact that due to direct contact of these areas with the ground etc. the vessels in these areas remain pressurised and do not get any scope to be distended by the settling blood. Rather, whatever amount of blood these vessels contained, is compressed out. The areas of contact palor is similar with the areas of contact flattening.
5. In drowning cases either the staining appears on the face and the neck or it does not appear at all. When the body remains submerged in water for some hours without being disturbed by waves or flow of the water, the head being the heaviest part of the body assumes lower level in comparison with rest of the body and the blood settles over the head and neck and the staining becomes apparent over the face and the neck. But, in flowing water or due to strong waves, the position of the body constantly changes. Hence, in these cases, there is no fixed dependant part of the body, so as to allow settling of blood in any part. Hence, in such circumstances there will not be formation of the postmortem staining in any part of the drowned dead body.
6. Antemortem hypostasis may be formed in persons with feeble circulation, if he has not changed his position for some hours.
Factors influencing the formation of the postmortem staining —
1. Fixed, undisturbed positioning of the dead body, for some hours after death is necessary. If the position of the body is disturbed then, there will be either no formation of the postmortem staining or the staining will be faint and may have extended distribution.
2. Due to excessive loss of blood during or before death or in severely anaemic subjects, post mortem staining may not be appreciable.
3. Post mortem staining is more prominent m fair-complexioned persons and is less conspicuous in dark-complexioned persons.
4. Post mortem staining is well formed in case of death due to asphyxia.
1. Formation of postmortem staining is a sign of death as it forms only after the cessation of circulation. But ante-mortem hypostasis may be there during the terminal phase of a living subject whose circulation has become very feeble and who is unable to change his position and has stayed in one position for a long period.
2. From the formation, size, extension and fixation of the postmortem staining, time passed after death can be roughly assessed. At the dependant aspects of the body, it starts appearing in small patches, by the end of the first hour. Postmortem staining is complete by about 6 hours after death. Fixation of the post mortem staining occurs by about another 5-6 hours after its formation.
3. Cause of death — From the distribution and the colour of postmortem staining some idea about the cause of death can be made.
(a) From the distribution of the postmortem staining — In cases of death due to hanging, if the body remains suspended in the upright position for a few hours, then, postmortem staining will appear in the lower limbs, lower parts of the upper limbs and at the upper margin of the ligature mark on the neck. When the body is suspended in the upright position, the limbs are the dependant parts of the body. The blood from the head cannot run down beyond the upper margin of the ligature and hence, postmortem staining also appears at the upper margin of the ligature mark.
|1. Situation||On the dependant parts of the dead body||Anywhere.|
|2. Tissue level||Undersurface of the skin and the skin level externally||Subcutaneous tissue level externally.|
|3. Surface||(a) Not elevated
(b) Cuticles not damaged
|(a) May be slightly elevated.
(b) Cuticles may be damaged in the form of abrasion.
|4. Margin||Sharp and clearly defined||Diffused margin.|
|5. Colour||Bluish or reddish purple normally. Specific colour in some specific poisoning death cases||Reddish when fresh which changes in colour with time.|
|6. Cause||Due to capillo-venous distension with blood||Due to extravasation of blood from capillaries.|
|7. Nature of the change||Postmortem||Antemortem.|
|8. Effect of pressure||Pressed spot appears pale||No change on application of pressure|
|9. Cut section||Cut surface shows oozing of blood from the smaller vessels which can be cleaned by washing||Cut surface shows evidence of haemorrhage in the tissue which cannot be washed out (In dead bodies).|
|10. Microscopic study||Engorgement of capillaries||Extravasation of blood, cellular infiltration etc.|
|11. Enzymatic study||No change||Change in the level of certain enzyme, in the affected area.|
|12. Medicolegal importance||Tells about the time of death and position of the dead body||Tells about the nature of injury, weapon used etc.|
|1. Situation||Dependant part of the organ||Whole or any part of the organ, affected with the pathology.|
|2. Cut surface||Oozing of blood from the distended capillaries||Exudation of fluid, mixed with blood, from the cut surface.|
|3. Swelling or oedema||Nil||May be appreciable.|
|4. In case of stomach and intestine, when stretched||Depending on ridges and creases of the stomach and intestine there will be lines and areas of discolouration and paleness||Uniform hyperaemia.|
|5. Cause||Passive capillovenous distension||Due to some pathology in the organ.|
|6. Nature of change||Postmortem||Antemortem.|
Though in cases of death due to hanging, if the body remains suspended for some hours after death in the upright position, the postmortem staining will appear on the limbs and upper margin of the ligature mark, yet, presence of postmortem staining over these areas of the body should not alone essentially mean that, death was due to hanging. Because, if a person is suspended in upright position with a ligature around the neck, after being killed by some other means, then also the distribution of the postmortem staining will be similar. Post mortem staining is just a POSTMORTEM PHENOMENON.
(B) From the colour of the postmortem staining — The normal colour of the postmortem staining is either bluish or reddish purple. But in some specific causes of death the colour of the postmortem staining may be different than the usual.
(i) In death due to HCN poisoning the colour of the post mortem staining is cherry red.
(ii) In KCN or NaCN poisoning the colour is brownish.
(iii) In CO poisoning the staining is pinkish.
(iv) In case of aniline or CO2 poisoning it is deep blue, due to excess of reduced haemoglobin.
(v) In case of phosphorus poisoning the colour is dark brown.
(vi) In case of H2S poisoning the colour is greenish blue, due to partial formation of sulphmeth-haemoglobin.
(vii) In case of death due to exposure to cold, the colour of the staining is bright red due to non-utilisation of the oxygenated blood, due to lack of metabolic functions of the body.
(viii) In case of drowning death and submersion of the body for some period in water, the postmortem staining at some places may be red due to formation of oxyhaemoglobin in the blood in the surface capillaries, due to absorption of oxygen through the body surface, from the water.
(ix) In case of death due to burning inside a closed room the staining may be bright red or pinkish due to formation of carboxy-haemoglobin due to inhalation of CO, a product of incomplete combustion of carbonaceous materials.
4. From the distribution of the postmortem staining the position in which the body was left for some hours after death can be known. If the distribution of the staining does not match with the position of the body in which it was discovered, then, it can be deduced that, the body was moved or manipulated after about at least some hours of death.
5. Postmortem staining, particularly when patchy and small in the early phase of its formation, may be confused with bruise.
6. Post mortem staining, particularly of the internal organs may be confused with congestion of the organs.
7. Haemorrhagic spots on skin of some parts of the body, due to blood dyscrasias, may be mistaken for postmortem staining. Postmortem staining is on the dependant parte of the body and when the body is in supine or prone position are symmetrical in distribution on both sides.
8. Some extraneous colour or stain may be mistaken as postmortem staining. These extraneous stains or colours can be wiped out or rubbed or washed out. But the postmortem staining cannot be so done. Moreover the distribution of the stain should also be differentiating.