Computerized tomography-derived body composition metrics are associated with 24-h urine lithogenic parameters.

Background: The relationship between body composition and lithogenic urine parameters remains poorly defined. This study aimed to evaluate associations between computerized tomography (CT)-derived body composition metrics and 24-h urine findings. Methods: Stone-forming patients in our Nephrolithiasis Database who underwent 24-h urine testing and CT within 120 days were retrospectively reviewed. Skeletal muscle index (SMI), visceral adipose tissue index (VATI), subcutaneous adipose tissue index (SATI) and skeletal muscle density (SMD) were calculated from segmented L3 axial images. Spearman correlations and multivariable logistic regression tested associations between body composition and 24-h urine markers. Results: Among 443 patients, all body composition metrics demonstrated numerous correlations with 24-h urine marker values on Spearman analysis. After adjusting for confounders, higher SMI quartiles were associated with increased odds of elevated urine volume (OR 2.13-2.71), hyperoxaluria (OR 2.11), hyperuricosuria (OR 2.60) and hypernatriuria (OR 2.70). Higher VATI was associated with reduced odds of elevated urine volume (OR 0.44), SATI with elevated sodium excretion (OR 2.35-2.38) and higher SMD with decreased odds of elevated oxalate (OR 0.50) and hypocitraturia (OR 0.41). Conclusions: CT-derived body composition metrics show distinct and clinically meaningful relationships with 24-h urine profiles. Muscle mass, adipose distribution and muscle quality each influence lithogenic risk, supporting incorporation of body composition assessment into metabolic evaluation of stone-forming patients.