Characteristics of diffusion-weighted and blood oxygen level-dependent magnetic resonance imaging in Tubulointerstitial nephritis: an initial experience

BACKGROUND: Diffusion-weighted (DW) and blood oxygen level-dependent (BOLD) magnetic resonance imaging are classical sequences of functional MR, but the exploration in non-transplanted kidney disease is limited. Objects: To analyze the characteristics of apparent diffusion coefficient (ADC) and R(2)* value using DW and BOLD imaging in tubulointerstitial nephritis (TIN). METHODS: Four acute TIN, thirteen chronic TIN patients, and four controls were enrolled. We used multiple gradient-echo sequences to acquire 12 T2*-weighted images to calculate the R(2)* map. DW imaging acquired ADC values by combining a single-shot spin-echo echo-planar imaging pulse sequence and the additional motion probing gradient pulses along the x,y, z-axes with two b values:0 and 200, as well as 0 and 800 s/mm(2). ATIN patients performed DW and BOLD magnetic resonance at renal biopsy(T(0)) and the third month(T(3)). We assessed the pathological changes semiquantitatively, and conducted correlation analyses within functional MR, pathological and clinical indexes. RESULTS: In ATIN, ADCs were significantly lower(b was 0,200 s/mm(2), 2.86 ± 0.19 vs. 3.39 ± 0.11, b was 0,800 s/mm(2), 1.76 ± 0.12 vs. 2.16 ± 0.08, P < 0.05) than controls, showing an obvious remission at T(3). Cortical and medullary R(2)* values (CR(2)*,MR(2)*) were decreased, significant difference was only observed in MR(2)*(T(0) 24.3 ± 2.1vs.T(3) 33.1 ± 4.1,P < 0.05). No relationship was found between functional MR and histopathological indexes.MR(2)* had a close relationship with eGFR (R = 0.682,P = 0.001) and serum creatinine(R = -0.502,P = 0.012). Patients with lower ADC when b was 0,200 s/mm(2) showed more increase of ADC(R = -0.956,P = 0.044) and MR(2)*(R = -0.949,P = 0.05) after therapy. In CTIN group, lowered MR(2)* and MR(2)*/CR(2)* provided evidence of intrarenal ischemia. CTIN with advanced CKD (eGFR< 45) had significantly lower ADC(b200) value. CONCLUSIONS: We observed the reduction and remission of ADC and R(2)* values in ATIN case series. ATIN patients had concurrently decreased ADC(b800) and MR(2)*. The pseudo normalization of CR(2)* with persistently low MR(2)* in CTIN suggested intrarenal hypoxia.