Volumetric MRI assessment of perirenal hematoma following biopsy of native and transplanted kidneys.

backgroundPercutaneous renal biopsy (PRB) is the gold standard for diagnosing nephropathies but carries a risk of complications, most commonly perirenal hematoma (PH). Although usually minor, PH volume is rarely quantified, and ultrasound-the standard modality-has limited accuracy. Magnetic resonance imaging (MRI) enables precise volumetric assessment and may improve understanding of PH pathophysiology. MATERIALS AND

methodsThis retrospective study included 138 patients (104 with native kidneys, 34 with grafts) who underwent kidney MRI 36-48 h after PRB. PHs were manually segmented on T1-weighted Dixon water-only images. Predictors of large PHs (upper tertile of volume) were identified using logistic regression, and model stability was evaluated with leave-one-out cross-validation (LOOCV). As an exploratory analysis, apparent diffusion coefficient (ADC) values were obtained from diffusion-weighted imaging (DWI) maps to assess correlations between renal diffusivity and PH volume.

resultsPH was detected in 89.9% of cases. Median PH volume was significantly lower in grafts than in native kidneys (9.3 mL vs. 20.95 mL, p = 0.030). Graft status was an independent negative predictor of large PH, while kidney volume (KV), diastolic blood pressure (DBP), and proteinuria were independent positive predictors. The final model showed moderate discriminative performance (AUC = 0.708). Lower ADC values correlated moderately and negatively with PH volume (rho = -0.41, p = 0.009).

conclusionMRI volumetry enables precise assessment of PH after PRB. Larger KV, higher DBP and proteinuria predicted greater PH volume, while graft status was protective. Lower renal parenchymal ADC values may reflect microstructural alterations predisposing to increased PH volume but warrants further evaluation in future studies.