[Pathogenesis of renal calculi].

The prevalence of nephrolithiasis (12% of the population) is directly related to environmental risk factors including nutrition. Correlations have been demonstrated between activity of renal stone disease and excessive protein intake or low fiber diets, and cause-and-effect relationships have been suggested between prevalence of the disease and low urine volume due to underhydration. Indeed eating too much meat and drinking too little can expose certain subjects, but not all, to nephrolithiasis. Why? Populations at risk include subjects with medullary sponge kidneys who represent 10% of the patients with idiopathic calcium nephrolithiasis and those with mild metabolic hyperoxaluria who cannot activate pyridoxin to 5' pyridoxal phosphate. Defective intestinal absorption of citrate and modifications in protein structures which inhibit urinary crystallization have also been observed. Clearly, many apparently normal subjects are overly susceptible to nephrolithiasis and the "explosion" would appear to be programmed if they are exposed to additional risk factors. Thus our theory of the powder keg and the tinderbox.