THE CONTINUALLY changing biology of human infections leads to confusion for the clinician who has not yet been impressed with the variations it can bring in clinical phenomena. If he is middle-aged or older, he has already learned by observing the change and does not ask whatever happened to lobar pneumonia, or why, all of a sudden, are cytomegalic diseases enjoying a spectacular ascendency? If the clinician is a recent graduate, he is likely to be confounded as he finds that his patients do not demonstrate the manifestations he expected from his textbook studies.
Thirty years ago, pyogenic liver abscess behaved as a straightforward, predictable clinical problem. It was blatantly overt, immediately advertising both its nature as an active, acute, septic process and its location within the liver. The clinician could expect to be led directly to the liver by the location of pain and convincing signs of tenderness over