Waist-to-height ratio as a non-invasive marker of renal sinus fat: a MRI-based cohort study

Background and aims Renal sinus fat (RSF) is an ectopic fat depot whose expansion has been linked to hypertension and chronic kidney disease. We assessed a range of adiposity indices to determine whether they offer more accurate predictions of RSF than BMI. Methods and results Renal sinus fat (RSF) and RSF relative to total kidney area (RSF%) were assessed via MRI in 74 individuals with severe obesity and 47 lean volunteers. 50 persons with obesity were re-evaluated 6 to 12 months after undergoing bariatric surgery. In multivariable regression analyses adjusted for age, sex, and BMI, the Body Roundness Index (BRI), waist-to-height ratio (WHtR), and waist circumference showed the strongest associations with RSF. Of these, only WHtR was significantly associated with RSF%. In univariate analyses, both RSF and RSF% were inversely correlated with estimated glomerular filtration rate (eGFR); however, in multivariate analysis, only RSF% remained independently associated with eGFR. Post-bariatric surgery, RSF change correlated with changes in WHtR and BRI. Conclusion Adiposity measures incorporating waist circumference are associated with RSF independent of BMI. While RSF exhibits a stronger relationship with adiposity measures, RSF% predicts eGFR. Both metrics offer complementary insights and should be considered in future studies.