Diffusion weighted imaging and blood oxygen level-dependent MR imaging of kidneys in patients with lupus nephritis

Background: Lupus nephritis (LN) is one of most common secondary glomerulonephritis. There is no ideal method to simultaneously assess renal structure and function in patients with LN. The aim of this study is to investigate the utility of diffusion weighted imaging (DWI) and blood oxygen level-dependent (BOLD) MR imaging in the assessment of renal involvement and pathological changes in patients with LN. Methods: Sixty-five patients with LN and 16 healthy volunteers underwent coronal echo-planar DWI and BOLD MR imaging of the kidneys. The apparent diffusion coefficient (ADC) and R2* values of the kidneys were calculated with b values of 0 and 500 s/mm(2). The relationship between the renal injury variables and the ADCs or R2* values were evaluated. And 16 of 65 patients with LN underwent a repeated evaluation after the induction treatment for 9 to 12 months. Results: The mean ADC values of kidneys in patients with LN were 2.40 +/- 0.25 x 10-3 mm(2)/s, the mean R2* values of the renal cortex and medulla were 11.03 +/- 1.60/sec and 14.05 +/- 3.38/sec respectively, which were all significantly lower than that in volunteers. In patients with LN, the mean ADC values were correlated with eGFR (r = 0.510, p < 0.01). There was a negative correlation between the mean ADC values and renal pathology chronicity indexes (r = -0.249, p < 0.05), the R2* values of the renal medulla and proteinuria (r = -0.244, p < 0.05), and the degree of tubulointerstitial lesions (r = -0.242, p < 0.05). The ADC and R2* values of kidneys were significantly higher than those of pre-treatment in complete remission patients. Conclusions: DWI and BOLD MR imaging of kidneys may be used to noninvasively monitor the disease activity and evaluate therapeutic efficacy in lupus nephritis.