Obesity and reduced renal corticomedullary differentiation on T1 mapping: a population-based UK Biobank study.

PURPOSE: This study aimed to explore the association between obesity and renal parenchymal heterogeneity on T1 map in the general population. METHODS: This population-based study included participants who underwent renal T1 mapping in UK Biobank imaging cohort. Obesity indices were body roundness index (BRI) and body mass index (BMI). The primary renal imaging parameter was corticomedullary T1 differentiation (ΔT1), quantified by manual region-of-interest placement in bilateral kidneys. Multivariable linear regression sequentially adjusted for sociodemographic, metabolic, and renal covariates. RESULTS: A total of 4214 participants (1812 men, 2402 women; 53.9 ± 7.6 years) were included. Both BRI and BMI were significantly and negatively associated with ΔT1 in fully adjusted models (BRI: β = - 8.507, 95% CI - 11.893, - 5.120; BMI: β = - 6.844, 95% CI - 10.124, - 3.565; both p < 0.05). BRI showed a significant inverse association with both medullary T1 and cortical T1 in fully adjusted models (β = - 0.104, 95% CI - 0.139, - 0.068; - 0.040, 95% CI - 0.075, - 0.005). BMI was also inversely associated with both medullary T1 (β = - 0.103, 95% CI - 0.137, - 0.069) and cortical T1 (β = - 0.068, 95% CI - 0.102, - 0.034). Age was strongly positively associated with cortical T1 (BRI: β = 0.169, 95% CI 0.128, 0.209; BMI: β = 0.160, 95% CI 0.119, 0.200) but not with medullary T1 (p = 0.535 and 0.956, respectively). CONCLUSION: Obesity indices are consistently associated with reduced ΔT1, primarily reflecting lower medullary T1, whereas age was associated with larger cortical T1 in general individuals.