Renal stone formation. The inhibitory effect of urine on calcium oxalate precipitation.

The mechanism of renal stone formation is not fully understood. This report describes an investigation into the effect of urine on the precipitation of calcium oxalate from dilute solution. Over 33 min a 5 per cent solution of urine caused considerable inhibition of precipitation. The degree of this inhibition was related to the concentration of the original urine. An "artificial urine" composed of 12 solutes present in normal urine had some inhibitory effect, but less than that of equiosmolar true urines. Inhibition was also related to the percentage of urine present. This inhibitory effect may be important in the prevention of renal stone formation in normal people by delaying crystallization until urine reaches the lower urinary tract.