[Infrared spectroscopy in the quantitative determination of urinary calculi constituents (author's transl)]

Infrared spectroscopy of urinary calculi can be used for the quantitative determination of the major constituents in mixed stones; the method is simple and consists in area-measurements of specific absorption peaks of the spectrum of each compound. In the area-measurement method the average error is +/- 2,5% in calcium-oxalate-apatite and +/- 2% in ammonium magnesium phosphate-carboapatite mixtures; within these limits the calculus matrix do not affect significantly the value of areas. An investigation of 64 mixed renal stones shows that in 57% of the samples, apatite is present in the nucleus; uric acid and calcium-oxalate are the most frequent superficial compounds, while the external layer of ammonium magnesium phosphate and the mixture uric acid-calcium phosphate are rare events. In calcium-oxalate-apatite and ammonium magnesium phosphate-carboapatite calculi the quantitative composition of the nucleus and the external layer differ significantly. The proposed method of analysis of internal and external structures in renal calculi can be useful for the study of etiology, for the prevention and the treatment of urolithiasis.