MINERALOGICAL COMPOSITION, STRUCTURE AND LITHOLYSIS OF URATE URINARY STONES FOR PATIENTS OF IVANOVO REGION

The quantitative mineralogical and chemical composition of urate urinary stones has been investigated using the X-ray powder method, scanning electron microscopy and X-ray spectral microanalysis for twenty five patients with urolithiasis of the Ivanovo region. The texture and surface composition of calculi have been carefully investigated and the peroral litholysis was simulated under laboratory conditions with dilute aqueous solutions of various pH values. The local change in the surface chemical composition for four stones during their destruction has been also studied via the X-ray spectral microanalysis. The main minerals of urate calculi are pure uric acid and insignificantly uric acid hydrates. No calculi composed of uric acid salts are observed. The main chemical elements of their surface are carbon, nitrogen and oxygen. The interaction of urate stones with litholytic solutions leads to a gradual decrease in their size, the effect being much more pronounced for smaller calculi. The results of X-ray spectral microanalysis show that the surface composition of stones composed of pure uric acid is almost constant during the treatment. Our results clearly indicate that oral litholysis of urate stones with appropriate citrate mixtures should be approached differentially depending on the composition of the calculus. In particular, for urate stones containing an appreciable amount of calcium oxalate hydrates, vitlocite or uric acid salts, litholytic therapy should be mainly applied as an additional technique to the extracorporeal shock wave or contact lithotripsy. For larger uric acid calculi, in turn, the effect of litholytic citrate monotherapy may be observed not earlier than after two or three months of oral administration of citrate mixtures.