Calcium oxalate kidney stone morphology reflects underlying metabolic and clinical conditions.

INTRODUCTION: Nephrolithiasis is a growing public health problem due to dietary changes and global warming. Physical analysis of the composition of urinary stones is recommended to guide treatment but is not always available. A morpho-constitutional classification of kidney stones dividing the prevalent calcium oxalate stones into type I (COM/whewellite Ia-Ie subtypes, related to hyperoxaluria) and type II (COD/weddellite IIa-IIc subtypes, related to hypercalciuria) was proposed several decades ago. The objective was to validate whether the morphology of calcium oxalate stones can guide diagnosis and actually reveal alterations in urine composition. METHODS: This study used intact and homogeneous calcium oxalate stones (Ia, IIa, Ic, Ie) accompanied by complete metabolic data. The stones underwent stereomicroscopic morphological evaluation and FTIR spectroscopy for accurate classification. Patients underwent standardized 24-h urine and fresh urine assessments to determine key lithogenic parameters. RESULTS: The morphologies of calcium oxalate stones correlate with specific conditions. Type II stones are associated with hypercalciuria, while type Ic and Ie stones are associated with dramatic hyperoxaluria, as seen in primary hyperoxaluria and enteric hyperoxaluria, respectively. CONCLUSION: Morphological analysis of calcium oxalate stones should be considered, as it provides specific information and can reveal rare but serious conditions and guide treatment. In the era of artificial intelligence, automated imaging could provide relevant information even in the absence of infrared or X-ray-based stone analysis methods.