Changes in the composition of urinary tract stones.

An increase in the average calcium oxalate content and decrease in average calcium phosphate content of stones received for analysis has been noted in a 9-year study. These changes appear to be due to a progressive increase in the number of patients with noninfected upper urinary tract stone and to the gradual elimination of phosphatic stones as a result of improved diagnosis and treatment. Some of the conditions associated with calcium phosphate stones are examined, particularly primary hyperparathyroidism, renal tubular acidosis, and medullary sponge kidney. These results further emphasize the importance of calcium oxalate in idiopathic stone disease and the need for a fuller understanding of the factors influencing calcium oxalate crystallization.