Effects of ethylenediaminetetraacetic acid-4 sodium solution on the surface of renal calculi and the uroepithelium.

Tetrasodium ethylenediaminetetraacetic acid is one of the most effective agents that dissolve renal calculi, especially calculi containing calcium. To study the dissolving process of calculi in solutions, with or without trypsin, serial thin sections of renal calculi composed of calcium oxalate and/or phosphate were prepared and observed by polarizing microscopy. The effects of the solution on the surface of human renal calculi and rat uroepithelium also were studied by scanning electron microscopy. A remarkable difference in solubility was noted between the crystalline and the amorphous components in struvite calculi. Under the polarizing microscope the dissolving effect of 5 per cent tetrasodium ethylenediaminetetraacetic acid solution on struvite after 30 minutes of incubation was equivalent to the use of saline for 24 hours. The effect of trypsin was not apparent. However, under the scanning electron microscope trypsin accelerated the dissolving effect of the tetrasodium ethylenediaminetetraacetic acid solution in struvite and calcium oxalate calculi. The contradictory findings of the ineffectiveness of trypsin on the thin sections as opposed to the pronounced changes seen on the surface of the calculi could be attributed to the difference in the exposed area. The results suggest that trypsin does not seem to dissolve calculi but mainly facilitates the solution to permeate the calculi. The cellular arrangement of the uroepithelium was preserved in tetrasodium solution and in 0.04 per cent trypsin tetrasodium ethylenediaminetetraacetic acid solution.