Feasibility of using blood oxygen level-dependent magnetic resonance imaging to evaluate renal fibrosis of ureteral obstruction of rabbits

Abstract

Objective: To investigate the feasibility of blood oxygen level-dependent MR (MR-BOLD) in assessing renal fibrosis of ureteral obstruction of rabbits. Methods: Forty healthy New Zealand rabbits were randomly divided into control group (n=8) and unilateral ureteral obstruction (UUO) group (n=32). The rabbits in the UUO group were subjected to unilateral ureteral obstruction of the left kidney.Coronal T(2) weighted imaging (T(2)WI) and axial BOLD examinations were performed before operation, 2, 4, 6 and 8 W after operation (each subgroup n=8). After the examinations, nephrectomy was performed for histologic evaluation.The T(2)(*) relaxation rate of the renal cortex (CR(2)(*)) , medulla (MR(2)(*)) and the same level of muscle(R(2)(*)(muscle)) were measured separately.The normalization of the cortex and medulla (sR(2)(*)), and the difference of sR(2)(*) between renal cortex and medulla before and post UUO (ΔsR(2)(*)) were calculated.The differences of sR(2)(*) (sCR(2)(*), sMR(2)(*), sCR(2)(*)(control), sMR(2)(*)(control)) at each time point between control and UUO group were compared by using independent sample t test.The LSD test was used to compare the sR(2)(*) in the control with that in the UUO group.The ΔsCR(2)(*) and ΔsMR(2)(*) values of the subgroups at UUO 2, 4, 6 and 8 W were compared by independent sample t test. Results: The sR(2)(*) values of UUO group were all lower than those of control group (all P<0.05), while sR(2)(*)(control) and sR(2)(*) in UUO group before operation were not significant different (P>0.05). The sCR(2)(*) values of UUO 2, 4, 6 and 8 W were 0.32±0.01, 0.37±0.01, 0.47±0.02 and 0.50±0.03.The sMR(2)(*) values were 0.39±0.02, 0.48±0.02, 0.58±0.04 and 0.65±0.05.There were significant differences of sCR(2)(*)(between) UUO 2 W and 6 W, UUO 2 W and 8 W, UUO 4 W and 6 W, UUO 4 W and 8 W (all P<0.01). There were significant differences of sMR(2)(*)(between) UUO 2 W and 6 W, UUO 2 W and 8 W, UUO 4 W and 8 W (all P<0.01). No significant difference was founded between sCR(2)(*) and sMR(2)(*) at each time point in control group (P>0.05). The ΔsCR(2)(*) values of UUO 2, 4, 6 and 8 W were 0.31±0.02, 0.20±0.02, 0.14±0.20, 0.09±0.04; the ΔsMR(2)(*) values were 0.51±0.05, 0.36±0.04, 0.28±0.05, 0.19±0.05. The ΔsCR(2)(*) values of UUO 2, 4 and 6 W were less than ΔsMR(2)(*) (P<0.05). There was no significant difference between ΔsCR(2)(*) and ΔsMR(2)(*) in UUO 8 W (P>0.05). Conclusions: The R(2)(*) change in medulla resulted from renal fibrosis is more significant than cortex.MR-BOLD can reflect the process of renal fibrosis.It's feasible and of great value to use renal MR-BOLD for the assessment of renal fibrosis induced by unilateral ureteral obstruction.