The Chest X-ray in this picture was from a man, an ex-smoker, who was losing weight, with a cough and localised wheeze in his chest. An area of density in the lung on the X-ray was obscured by blood vessels and it was determined as normal. Because the test was described as normal, clinical signs and symptoms were disregarded, no further tests were done, and the man presented months later with a large inoperable cancer. A court case followed.
A radiological diagnosis is not etched in stone. Over a long career I have been involved with many cases of physical child abuse, and for many of these been called as an expert witness in a trial of the accused abuser. It was during these trials where I discovered that medical evidence and legal evidence are two entirely different things.
Medical evidence is often fuzzy relying on statistical likelihood of a diagnosis based on imperfect criteria – sounds heard through a stethoscope, lumps palpated with the hand for example. The art of medicine is about management of uncertainty. Legal requirements on the other hand are for precisely defined points. Lawyers, and many doctors, treat a radiological image as hard, clearly defined evidence; the experience of my career tells me it is anything but!
Paradoxically, as imaging becomes more sophisticated and sensitive the importance of clinical judgement in deciding both when to order a test and to assess the clinical relevance of an abnormal finding on that test becomes more important. Real but incidental sub-clinical anatomical disorders such as normal developmental variants and degenerative changes that are not symptomatic are frequently detected. These types of changes are present in a large proportion of people with no symptoms. It is therefore important to know that a test should not be ordered unless it is likely to influence or change the treatment of a patient (although there are a few exceptions even to that rule).
Many types of errors creep into diagnosis, and it can sometimes be difficult to trust one’s own judgement. This phenomenon has been extensively studied, but the following example will serve to illustrate just one type of error in which the context determines interpretation. In the top line most people read A B C. However, exactly the same letter B when inserted into another context now reads as 13. In this type of framework the image itself can be treacherous.
The Belgian surrealist painter, whom I greatly admire, René Magritte’s painting of a pipe “Ceci n’est pas une pipe” whose correct name is “The treachery of images” has fascinated me since I began studying radiology. It is about the relationship of an object and a representation of that object.
The word is not the thing; the map is not the territory (Alfred Korzybski). And so, the X-ray is not the patient. It is a well-known, but poorly understood , medical aphorism; “Treat the patient, not the X-ray”. And so it should be.