Reflection on the evolution of medical research in the tropics suggests that the diseases were studied initially because they were exotic and because they threatened the health of residents and travelers. Another facet of research value was often overlooked; the usefulness of tropical diseases as models for understanding more ubiquitous conditions. In the tropical world some conditions occur with extraordinary attack rates due to unique cultural, genetic or ecological factors; this allows unparalleled opportunities to gather large numbers of observations in a short period. Perhaps no better illustration of this phenomenon exists than epidemic bladder stone disease of children.
Once common throughout the Western world, urinary bladder stones now are limited to focal areas of many countries in Asia and the Middle East. In rural Northeast Thailand, for many decades, hospitalizations for the removal of bladder stone have exceeded 500 per one million inhabitants per year.