Pathology is the study and analysis of diseased body organs and cells. Pathologists (doctors who specialize in pathology) normally work in laboratories, and if a pathology test is ordered, you are unlikely to meet the pathologist in the normal course of events.
For a pathology test to be carried out, a sample of body tissue or fluid will be taken and sent to the laboratory for analysis. The sample might be of blood, urine, feces, sputum, pus, a discharge of some kind such as from the vagina or penis, cerebrospinal fluid (from the brain or spinal cord), fluid drawn out from a joint or a cyst, or tissue obtained by scraping or biopsy. The sample may be taken by the doctor, but more commonly you will visit a central pathology clinic where it will be taken by a trained nursing sister. If, for example, a biopsy or a sample of cerebrospinal fluid is needed, you may have to go to hospital.
Samples taken by the doctor or at the clinic will be sent by courier to a laboratory. Modern laboratories are usually large organizations with 20 to 200 staff or more. The sample will be tested by a medical technologist under the pathologist's supervision. If the required tests are complex, a scientist may be called in to help, and the pathologist may examine the specimen, especially if a finding is unusual.
The first examination will usually be under a microscope. This may be in the specimen's natural state, or it may be stained with a dye so that its various elements can be isolated (e.g. acids respond to one particular stain whereas alkaline elements react to a different one). Some of the sample may then be cultured. This means that it is added to a culture medium, which is usually a liquid or jelly-like substance containing nutrients in which bacteria or other micro-organisms will grow. The culture is incubated for a period, and if the bacteria or other organisms do in fact grow, they can be identified under a microscope or by various tests. If necessary, the organisms can be tested to see if they are sensitive to antibiotics, and if so, to which ones.
Once the results are obtained they will be fed into a computer for collation. If a serious disease is detected, the doctor who ordered the test will be telephoned with the result. Printed results are sent back by courier to the doctor's office.
Depending on what tests are necessary, the results will be available in a day or so, or in a couple of hours if it is an emergency. Culturing may take a couple of days, in the case of bacteria, or possibly several weeks if a virus is involved.
Almost any part of the human body or its secretions can be tested for disease. Urine samples can be tested to see if the patient is taking medication, or has infections or gout. Feces can tell a pathologist if the patient is absorbing food properly, or keeping to a diet. The fluid around the brain and spinal cord will provide details of a head injury or infection. Cancer can be detected in many different tissues that a surgeon has removed. If cancer is suspected during an operation, a pathologist may be called to the operating theater to examine the tissue under a microscope so that the surgeon can decide how to finish the operation. Cancer of the cervix can also be detected at a very early stage by the pathologist's examination of the Pap smear that all women should have every year or two. Unusual tests can be performed on sweat to check for cystic fibrosis (an inherited lung disease in children), on the fluid around the baby in the womb to detect congenital diseases and to find out its sex, on semen to determine a man's fertility, on the fluid in joints for arthritis, and on bone marrow to detect leukemia.