Risk Factors in stone-formation

Abstract

It has been shown in previous communications (Robertson et al., 1969, 1971, 1976b; Robertson and Peacock, 1972) that the two main chemical factors which determine the risk of forming calcium oxalate-containing stones are the degree of saturation of urine with calcium oxalate and calcium phosphate and the level of protective inhibitory activity against the crystallisation of calcium oxalate. Since urinary calcium, oxalate and pH are the major determinants of the saturation of urine with calcium salts (Robertson and Nordin, 1976), it is likely that the risk of forming stones is related to the levels of these constituents in urine. Thus the higher the excretion of these ions the greater the risk of forming stones. Similarly, it is likely that the risk of forming stones is related to the concentration of urinary inhibitory activity, the majority of which has been shown to be in the acid mucopolysaccharide (AMPS) fraction of urine (Robertson et al., 1976). It has also been shown that the effective concentration of AMPS may be reduced in urines containing high concentrations of uric acid (Robertson et al., 1976a).Thus there appear to be five main urinary constituents which influence the risk of large crystals of calcium oxalate forming in the urinary tract viz. calcium, oxalate, pH, AMPS and uric acid.