Calcium and Oxalate Concentrations in Human Renal Tissue: The Key to the Pathogenesis of Stone Formation?

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Abstract
The intrarenal distribution of Ca and oxalate in man was studied to examine a possible relationship between Ca and oxalate concentrations in the renal tissue and stone formation. Fresh human renal tissue was obtained at operation from 7 subjects. The Ca concentrations in the papilla, medulla and cortex were measured by atomic absorption spectrophotometry. A radioenzymatic procedure was used to determine the corresponding oxalate concentrations. Significantly higher concentrations of Ca and oxalate were observed in the papilla compared to the medulla. The medulla, in turn, contained higher concentrations than the cortex. Ca and oxalate concentrations were 6 and 25 times higher in the normal papilla than in the urine, respectively. The ion product of calcium oxalate in the papilla is greatly in excess of the formation product. Thus far, oxalate concentrations in the human renal tissue have not been investigated, although the frequent finding of calcification in the renal papilla suggests that they may exist. The observed intrarenal Ca and oxalate concentration gradients seem to be a significant mechanism in the pathogenesis of papillary calcification and a strong indication for renal stone formation to start from fixed crystalluric particles in the papilla.