A necropsy is a postmortem examination that is sometimes called an autopsy, postmortem, or obduction. Some people like to use the term specifically for examinations that are performed on non-humans, reserving “autopsy” for humans specifically. Whether performed on humans or animals, necropsies can provide important information about the cause of death, and this information can be used in a wide variety of ways.
Necropsies on animals are routinely performed when a new disease breaks out, to determine which animals carry the disease and what the effects of the disease on animals might be. In areas where zoonotic diseases are endemic, one may be ordered on any suspicious animal death to determine what the animal died of and to see if the death should be a cause for concern. Scientific researchers also examine the subjects of their research to learn more about how their research is going.
During a necropsy, the person who performs the examination first inspects the exterior of the body, making notes for the record. These notes will include any signs of trauma, along with general observations about the subject's physical health. Evidence such as blood draws and samples of substances found on the body may also be collected at this time. Once this examination has been performed, the body is opened up, allowing the internal organs to be inspected.
Depending on the nature of the postmortem, samples may be collected from one or more of the internal organs for further study. For example, if a dog is necropsied after it has been put down due to suspected rabies, a sample of the brain tissue will be taken to test for the illness. Likewise, brain tissue samples may be taken from a downer cow to check for signs of a transmissible spongiform encephalitis (TSE). In the case of an autopsy on a human body, samples may be taken of the stomach contents to see what the person ate before death, and the heart and lungs will be examined for signs of disease.
When the cause of death is mysterious, a necropsy aims to clear up the issue. When the cause of death is known or obvious, the examination may be used to collect evidence about how the body came to die, if the death is suspicious, or to learn more about the course of the disease that eventually claimed the life of the person or animal being examined. In the case of scientific research, where test subjects are routinely euthanized after testing, the examination provides information about whether or not a drug or treatment worked, or about the progression of the disease or other issue under experiment.
Some people have advocated for routine necropsies, arguing that they can always provide more information about a death. Institutions like zoos always do them on the animals that die under their care, for example, to learn why the animal died and to prevent such deaths in the future. Autopsies on humans can also provide interesting information, even when the cause of death seems clear; researchers have discovered, for example, that some deaths ascribed to senility or Alzheimer's are actually TSEs.