Three-dimensional pseudo-continuous arterial spin labeling magnetic resonance imaging: an effective imaging technique for early-stage kidney injury in patients with type 2 diabetes.

Background: Functional biomarkers cannot currently detect hemodynamic impairment in patients with early-stage kidney injury and type 2 diabetes mellitus (T2DM). This study evaluated the utility of three-dimensional pseudo-continuous arterial spin labeling (3D-pCASL) magnetic resonance imaging (MRI) in quantifying stage-specific renal blood flow (RBF) alterations in patients with T2DM. Methods: A total of 33 patients with T2DM, who were divided into normoalbuminuria (NAU; n=11), microalbuminuria (MAU; n=13), and diabetic kidney disease (DKD; n=9), along with 15 healthy volunteers (HVs), were recruited. All participants underwent renal contrast-enhanced MRI and 3D-pCASL examinations on a 3.0-T scanner. Two experienced radiologists independently segmented the kidneys based on the postcontrast cortical phase images and measured the cortical RBF. The cortical RBF values across the four groups were compared via one-way analysis of variance, with post hoc multiple comparisons performed to analyze differences between specific renal segments. Correlation analyses were conducted between cortical RBF values and estimated glomerular filtration rate (eGFR), as well as other renal function parameters. Results: Despite having a normal eGFR, patients in the NAU stage exhibited significantly reduced RBF (right: 110.84±13.15 mL/100 g/min; left: 94.14±5.24 mL/100 g/min) compared to HVs [right: 133.78±19.19 mL/100 g/min; left: median, 109.00, interquartile range (IQR), 101.53-117.15 mL/100 g/min], with reductions of approximately 17-19% in the bilateral anterior segments (right: adjusted P=0.016; left: adjusted P=0.008). A progressive decline in RBF was observed across advancing disease stages in certain renal segments (e.g., posterior segments) in the NAU group (right: median, 104.57, IQR, 101.90-116.92 mL/100 g/min; left: 95.49±11.60 mL/100 g/min, MAU group (right: 92.07±13.13 mL/100 g/min; left: 82.40±6.76 mL/100 g/min), and DKD group (right: 69.52±17.16 mL/100 g/min; left: 65.75±19.36 mL/100 g/min). The posterior segment emerged as a consistently vulnerable region in the MAU and DKD stages (both adjusted P values <0.05), suggesting an anatomic predilection for injury, attributed to its terminal arterial supply with limited collateralization. Separate analyses indicated that in the NAU and MAU groups, RBF showed a positive correlation with eGFR (NAU: r=0.460, P=0.031; MAU: r=0.398, P=0.044; DKD: r=0.694, P=0.001) but no significant correlations with other clinical parameters. Furthermore, in the DKD group, RBF showed a positive correlation with the blood urea nitrogen-serum creatinine ratio (r=0.670, P=0.002) and inverse correlations with serum creatine (r=-0.633; P=0.005) and triglyceride level (r=-0.749; P<0.001). Conclusions: 3D-pCASL MRI enables detection of preclinical microvascular impairment in patients with T2DM, representing a sensitive biomarker for early DKD risk stratification. Quantification of RBF in the vulnerable posterior segment yields clinically actionable insights for targeted interventions before the onset of functional decline.