Background: Pediatric kidney transplant recipients require periodic biopsy for active surveillance to prolong allograft half‐life, and non‐invasive MR imaging markers are needed but understudied. Here we aimed to determine the feasibility of MR diffusion tensor imaging (DTI) on pediatric kidney transplant recipients, compare transplanted kidneys DTI values to healthy controls, and correlate DTI values with allograft histopathology. Methods: Single‐center prospective study of pediatric (< 18 years of age) kidney transplant recipients undergoing biopsies and healthy controls between February 2020 and October 2023. MRI DTI‐derived metrics (fractional anisotropy [FA] and track length) of the kidney cortex were obtained for all participants. Transplant recipients versus controls, rejection versus non‐rejection, and high chronic allograft damage index (CADI) versus low were compared using two‐sample t‐test or Wilcoxon rank‐sum test. Results: Fifteen transplant recipients (4F/11M, median 16 [IQR 13–18] years old) and 15 healthy controls (9F/6M, median 15 [IQR 12–22] years old, 30 kidney units) were evaluated. DTI was technically appropriate in all cases. Smaller FA values and longer track length were found in allografts (FA in allografts (median [IQR]: 0.25 [0.25–0.28]) vs. controls (0.28 [0.27–0.33], p = 0.003) and track length in allografts (mean: 19.36 ± 5.21) vs. controls (12.80 ± 3.34, p ‐value < 0.001). FA and track length between allografts with and without rejection, and/or with high vs. low CADI score were not significantly different. Conclusion: DTI in pediatric kidney transplants is feasible and showed differences in FA and track length values when compared to controls. However, in our limited dataset, DTI did not find differences within the allograft group.

A large dataset of pediatric US measurements and natural language processing was used to calculate kidney length and volume percentiles, resulting in increased normative value precision and highlighting growth patterns.