BASIC MECHANISMS IN UROLITHIASIS

THOUGH the mechanism of urinary calculus formation remains imperfectly understood, a number of contributing factors have been clearly established as important. Some of these factors can be simply demonstrated in experiments using rats with a surgically inserted foreign body in the bladder.¹ The foreign body serves as a uniform stimulus to stone formation, for such rats, even though maintained on a normal diet, consistently form a stone about the foreign body. In controlled experiments, if one or another of the supposed etiologic factors is removed, its significance becomes manifest in any difference in the weight of stone produced. By this method, the all-important factor of urinary concentration can be clearly demonstrated in several different ways. By inducing diuresis,² urinary dilution may become so great that stone formation no longer occurs. Stone formation is also completely prevented by reduction in the dietary intake of a single ionic component of