Rock-on or crumble: Do kidney stones pass the test of time? A European Association of Urology Section of Endourology study.

OBJECTIVE: Kidney stone disease is a relapsing disease and preventive measures are therefore of great importance. A cornerstone for adequate treatment and prevention of kidney stone recurrence is stone analysis. This pilot study aimed to evaluate whether time and different ex vivo environments, such as liquid media or light exposure, influence the morpho-constitutional aspects of kidney stones and whether these changes influence the outcome of X-ray diffraction (XRD) or morphoconstitutional assessment (MCA) for stone analysis. METHODS: Ninety-two stone fragments from 23 kidney stone patients were allocated to four groups (Group A, direct stone analysis; Group B, dry non-transparent environment; Group C, dry transparent environment; Group D, wet non-transparent environment). Fragments from Groups B, C, and D were photographed on postoperative day (POD) 0 and POD 84 and sent for stone analysis afterwards. The objective change in appearance was assessed through the mean Euclidean distance in the Commission Internationale de l'Éclairage L ∗ a ∗ b ∗ (CIELAB) color space. The agreement of XRD and MCA between POD 0 and POD 84 was evaluated. Spearman's rank correlation coefficient was calculated to assess the correlation between the objective changes in appearance and the diagnostic accuracy for XRD and MCA. RESULTS: Overall, the mean Euclidean distance was 5.52 between POD 0 and POD 84. XRD had an agreement between POD 0 and POD 84 of 98%. MCA had an agreement of 92%. The objective changes in appearance between POD 0 and POD 84 did not correlate with the diagnostic accuracy of XRD or MCA. CONCLUSION: The appearance of kidney stones alters over time and in different ex vivo environments but does not change the diagnostic accuracy of XRD or MCA.