HEALTH / Common Procedure: Biopsy

IN MEDICINE the final verdict comes from the pathologist who examines the body after death. The necropsy, followed by examination under the microscope of the structures of the internal organs, allows him (or her) to say with near 100 per cent certainty what was the precise cause of the person's final illness. In a few cases the puzzle may remain unsolved, one example being the hundreds of babies who die each year unexpectedly and without any apparent cause - the sudden infant death syndrome.

It is no consolation to a sick person to know that the illness that is baffling the doctors will eventually be explained by the pathologist after a necropsy. In fact, really puzzling illnesses have become rare with the development in the past 20 years of so many ways of examining the interior of the body during life. In addition to X-ray images, doctors may use magnetic resonance imaging, radio-isotopes and ultrasound to show detailed cross sections of all parts of the body, while fibreoptics and miniaturised video cameras allow direct or indirect inspection of all the body cavities. All these advances rely, however, on the interpretation by a clinician: pictures may sometimes be dark, blurred or ambiguous. A much more certain diagnosis may be reached if a pathologist examines under the microscope a small fragment of the organ thought to be responsible for the illness - the lung, liver, kidney, a piece of muscle, or blood vessel. The removal of the fragment - and its examination - is the procedure known as a biopsy.

Most biopsies are obtained by inserting a hollow needle with a cutting tip into the target organ. A local anaesthetic is given, the skin cleaned, and the needle is inserted and its position checked, often by ultrasound. The tip is then rotated and suction applied with a syringe; and if all goes well the needle will contain a thin sausage-shaped pEiece of the diseased part of the organ, which is given to the pTHER write errorathologist for examination. This takes some time, as the specimen has to be treated with chemicals, embedded in a firm wax, sliced into thin wafers, stained and examined. It is usually a week or two before the pathologist completes his report. In an emergency the pathologist may be willing to give an opinion within a few minutes if he freezes the specimen and then examines it, but this technique is not so reliable.

In many cases the question to be answered by the pathologist is whether or not a tumour or an ulcer is cancerous - is it benign or malignant? Screening for breast cancer by mammography often relies on a biopsy to establish whether there is cause for concern. Fortunately the answer is almost always clear-cut, and treatment can then be planned. Liver and kidney biopsies are often done to allow precise diagnosis of some kind of chronic inflammation, and repeat biopsies may be needed to assess the response to treatment. A biopsy of bone marrow is an essential step in the diagnosis of blood disorders such as leukaemia. The risk to the patient from these tests is very small; liver and kidney biopsies may be slightly hazardous in someone with a bleeding disorder, and in these circumstances the patient may be kept in bed for a few hours under close observation. In general, however, the gains from a biopsy far outweigh any minor discomfort.