Physical Analysis of Urinary Stone Using FT-IR

Lee, Soo Youn; Kim, Jong Won

Abstract

BACKGROUNDS: Stone analysis is essential to determine the possible cause of stone formation and treatment of urolithiasis. Physical analysis using Fourier transform infrared spectroscopy(FT-IR), compared to chemical analysis, requires minimal sample volume, shows uniform sensitivity and specificity to all components and provides quantitiative results with greater reproducibility. We compared urinary stone analysis using FT-IR and chemical ananlysis.
METHODS
From January 1996 to May 1999, 515 urinary stones were analyzed. For physical anlaysis, we used FT-IR system 2000(Perkin-Elmer Co., U.S.A.) and SpectrumTM software(Perkin-Elmer Co., U.S.A.). Chemical analyses for calcium, phosphate, uric acid, carbonate, magnesium, ammonia, oxalate and cystine were performed. Stone analyses with FT-IR were compared to those with chemical analysis. Clinical findings and the other laboratory findings including routine urinalysis, serum tests, and 24 hour urine test were also investigated.
RESULTS
We analyzed 515 urinary stones from 501 patients. Sex ratio was 2.8: 1 and mean age was 48 years. Physical analyses were performed in 515(100%) stones and 81.2% of them showed mixed composition. And 79.4% included calcium oxalate monohydrate or dihydrate. Calcium oxalate monohydrate(63.3%), uric acid(11.3%), calcium oxalate dihydrate(9.9%), and carbonate apatite(8.3%) were commonly found as a major component. Chemical analyses could be done in only 454 cases(88.2%) due to insufficient sample and the most common positive findings were calcium(50.0%), phosphate(33.0%), and uric acid(18.5%). Seventy-one cases(15.6%) with negative chemical reactions to all components were mixed stones except 9 cases. When the stone components were analyzed by FT-IR and chemical method, we found full agreements in only 2.3%, partial agreements in 56.3%, poor agreements in 11.5% and no agreements in 4.3% of total cases. Hypercalciuria and natriuresis were found in 36.1% and 23.0%, respectively. The pH of urine shows significant differences in uric acid and struvite stones compared to the pH of the others(P<0.05).
CONCLUSIONS
We found difficulties in detecting minor or mixed components of urinary stone and in analyzing small sized stone by chemical methods. Physical analysis using FT-IR can provide more accurate determinations of composition of urinary stones and can be significantly useful in diagnosis, treatment and prevention of urolithiasis.