Analysis of urinary calculi by infrared spectroscopy.

In the past 4 years, we used infrared spectroscopy to analyze 728 urinary calculi. The most common component of pure urinary calculi was calcium oxalate (whewellite and weddellite) 8.65%, followed by calcium phosphate (carbonate apatite, brushite and amorphous calcium phosphate) 6.87%, uric acid 5.91% and struvite 2.75%. The majority of urinary calculi had mixed components: whewellite/apatite 28.98%, weddellite/apatite 24.31% and whewellite/weddellite/apatite 14.42%. Only 3 cystine stones were found (0.41%). Good correspondence (82.7%) was noted when the results of 110 urinary calculi analyzed by infrared spectroscopy were compared with the results of polarization microscopy. The advantages and disadvantages of infrared spectroscopy are also discussed.