GENETIC AND DIETARY INFLUENCES ON URINARY OXALATE EXCRETION

Several genes contribute to the development of calcium oxalate nephrol ithiasis as it is a polygenic disease. To explore the influence of gen etic factors on oxalate excretion we have examined the distribution of oxalate excretions in 101 normal individuals who consumed self-select ed diets. The distribution was apparently trimodal, consistent with th e existence of three classes of oxalate excreters reflecting two allel ic genes determining high and low oxalate excretion occurring with fre quencies of 0.32 and 0.68 respectively. The pattern of inheritance in eight families was compatible with the expression of a pair of codomin ant alleles. A comparison of the distribution of excretory classes amo ng the 101 normal individuals with that of 101 calcium oxalate stone f ormers suggests that high oxalate excretion may be associated with a 4 -fold increased risk of stone disease and intermediate excretion with a 1.6-fold increase. Control of dietary factors influencing oxalate ex cretion apparently improved the discrimination between excretory class es in 17 individuals but the intraindividual variability in oxalate ex cretion was not reduced in four of nine individuals in whom this param eter was evaluated. More stringent dietary control than that applied i n this study may be required before more extensive genotyping of indiv iduals is attempted.