Ultrasound-Derived Differential Renal Volume Indexed to Recipient Body Mass Index Predicts One-Year Kidney Graft Function: A Novel Surrogate of Graft-Recipient Size Matching.

BACKGROUND

Appropriate matching between donor nephron mass and recipient metabolic demand is increasingly recognized as an important determinant of kidney graft outcomes. However, practical and widely applicable methods for estimating graft-recipient size matching remain limited. We investigated whether renal parenchymal volume measured by routine ultrasonography and normalized to recipient body mass index (BMI) is associated with kidney graft function one year after transplantation.

METHODS

In this prospective single-center study, adult kidney transplant recipients underwent routine ultrasonographic assessment one month after transplantation. Renal volumetric parameters, including total renal volume (TRV) and differential renal volume (DRV), were calculated and normalized to recipient BMI. Associations with estimated glomerular filtration rate (eGFR) at one year were evaluated using correlation and multivariable linear regression analyses adjusted for relevant donor and recipient characteristics. Receiver operating characteristic (ROC) analysis was performed to assess the discriminatory ability of the most informative volumetric index.

RESULTS

Renal volumetric parameters were significantly associated with one-year graft function, with stronger associations observed after normalization for recipient BMI. Among the evaluated indices, the DRV/BMI ratio showed the strongest correlation with eGFR and remained independently associated with one-year graft function after multivariable adjustment. Exclusion of renal sinus volume improved the predictive performance of volumetric assessment, supporting the relevance of functional renal parenchyma over total kidney volume. In exploratory ROC analysis, the DRV/BMI ratio demonstrated good discrimination for preserved graft function (AUC 0.774), although the identified threshold requires external validation.

CONCLUSIONS

Ultrasound-derived donor renal parenchymal volume indexed to recipient BMI represents a simple, non-invasive, and clinically applicable surrogate of graft-recipient size matching. If validated in larger multicenter cohorts, this approach may complement existing clinical parameters for predicting graft function and support more individualized post-transplant management.