Book excerpt: This is an A-Z reference guide to over 5000 medical terms including symptoms, diseases, drugs and treatments. Since the appearance of the first edition in 1990, significant developments have occured in many areas of medicine. For example, far more internal operations can now be performed by minimally invasive keyhole surgery. Genetic disorders, such as cystic fibrosis, are now understood in far greater depth than before. There has also been a dramatic increase in the number of screening tests for the early detection of diseases.