Objective:

To explore the feasibility and application value of arterial spin labeling (ASL) in evaluating the degree of renal fibrosis after kidney transplantation.

Methods:

This is a cross-sectional study. Renal transplant recipients who received treatment at the First Affiliated Hospital of Soochow University from December 2021 to December 2022 were enrolled. All participants underwent ASL scan, and the values of renal cortical renal blood flow (RBF) were measured through post-processing software. The participants were divided into different groups according to the Banff interstitial fibrosis score (ci score) of the transplanted kidneys, and then relevant indicators were compared. One-way analysis of variance was conducted to compare the differences in renal cortical RBF among the groups. Spearman correlation analysis was employed to investigate the association between renal cortical RBF and ci score of the transplanted kidney. Receiver operating characteristic curve was used to analyze the diagnostic effectiveness of renal cortical RBF and laboratory indicators for distinguishing varying degrees of fibrosis in transplanted kidneys. The Delong test was utilized to compare the area under the curve (AUC).

Results:

A total of 60 patients (42 males and 18 females) were included in the study, with a mean age of (44.6±10.8) years. All patients were divided into 4 groups ci0 group (ci score=0, 11 cases), ci1 group (ci score=1, 21 cases), ci2 group (ci score=2, 20 cases), and ci3 group (ci score=3, 8 cases). With an increase in the degree of fibrosis in the transplanted kidney, there was a corresponding decrease in the renal cortical RBF value. The differences in renal cortical RBF values among the 4 groups were statistically significant[ci0 group (214.9±28.5) ml·(100 g)-1·min-1; ci1 group (181.7±29.3) ml·(100 g)-1·min-1; ci2 group (158.8±39.2) ml·(100 g)-1·min-1; ci3 group (123.1±27.2) ml·(100 g)-1·min-1; F=14.02, P<0.001]. The renal cortical RBF was moderately negatively correlated with the ci score (r=-0.644, P<0.001). The AUC for discriminating between ci0 and ci1-3 of renal cortical RBF and 24-hour urine protein was 0.881 (95%CI 0.772-0.950) and 0.680 (95%CI 0.547-0.795), respectively. The AUC for renal cortical RBF was significantly higher than that for 24-hour urine protein (P=0.047). The renal cortical RBF can distinguish between ci0-1 and ci2-3, as well as ci0-2 and ci3, with the corresponding AUC value of 0.796 (95%CI 0.673-0.889) and 0.900 (95%CI 0.795-0.963), respectively.

Conclusion:

ASL can quantitatively assess renal blood perfusion in transplanted kidneys and demonstrates high operational efficacy in distinguishing varying degrees of fibrosis in the transplanted kidneys.