Assessing Stone Composition in Irrigation Fluid Using Raman Spectroscopy: A Blinded Comparative Study

Objectives: To assess the capability of Raman spectroscopy (RS) in the analysis of stone composition utilizing microscopic fragments from irrigation fluid during ureteroscopy (URS) and laser lithotripsy. Patients and Methods: A prospective, blinded study involving patients undergoing URS with laser lithotripsy. Irrigation fluid collected during the procedure was centrifuged, and microscopic particles were analyzed using RS. Simultaneously, stone fragments underwent formal analysis by Fourier-transform infrared spectroscopy (FTIR) in a different laboratory. The researcher conducting the RS was blinded to the results of the FTIR analysis. The RS results were compared with FTIR to evaluate concordance. Results: Between March 2022 and February 2023, 22 patients were enrolled. Stones were located in the kidney (41%), ureter (45%), and both (14%). The median stone size was 12 mm. RS accurately identified the major stone component in 82.6% (19) of cases, with a 17.4% (3) discrepancy. Concordance was observed for stones composed of calcium oxalate (CaOx) monohydrate/dihydrate, calcium phosphate, and uric acid. In discordant cases, FTIR identified CaOx monohydrate and dihydrate. Conclusions: This study introduces an innovative approach for analyzing stone composition using microparticles from irrigation fluid during stone fragmentation. The results demonstrated strong concordance with the standard FTIR technique, suggesting potential for stone analysis without the need to retrieve fragments during procedures. Further research is warranted to refine this method for broader clinical application.