Longitudinal evaluation of split renal function by dynamic contrast-enhanced MR renography in unilateral ureteral obstruction rat models

Background In case of acute urinary tract obstruction, only a few of the patients could restore full renal function if the obstruction is relieved after a long period of time. Therefore, to introduce an effective method to evaluate the residual renal function in obstructive nephropathy is very important for optimizing treatment and predicting the prognosis. Objective To investigate the longitudinal variation of split renal function in unilateral ureteral obstruction (UUO) rats by dynamic contrast-enhanced (DCE) MRI. Materials and methods Twenty one rats were randomly divided into seven groups who underwent low dose Gd-DTPA (0.04 mmol/kg) DCE MR at 6 h, 12 h, 24 h, 72 h, 1w and 2ws after UUO operation or sham operation as well. The volume of each kidney was measured. The time signal intensity curves (namely MR nephrogram, MRR) of renal parenchyma were plotted. The Baumann–Rudin model was used to calculate the clearance rate (k cl ) of Gd-DTPA from cortex to medulla. All rats were then scarified for pathological examination. Results The size of obstructive kidney was increased along with the obstruction time. The average k cl of obstructive kidneys of sham operation group and 6 h, 12 h, 24 h, 72 h and 1 week after UUO were 3.53 ± 0.31, 3.45 ± 1.06, 2.43 ± 0.35, 2.36 ± 0.23, 2.13 ± 0.42 and 1.73 ± 0.45/min, respectively. The k cl of obstructive kidney 2 weeks after the UUO couldn’t be calculated because of renal parenchyma atrophy. Similarly, the k cl of contralateral kidneys at the above time points after UUO were 3.33 ± 0.32, 3.15 ± 0.07, 3.20 ± 0.26, 3.90 ± 0.70, 2.87 ± 0.15, 2.97 ± 0.40 and 2.90 ± 0.68/min, respectively. The k cl of obstructive kidney was declined progressively over obstruction time and declined rapidly since the time point of 12 h ( P < 0.05). The k cl of contralateral kidneys comparing with the normal controls had no significant difference. The results were consistent with the pathological findings. Conclusions The clearance rate could reflect the change of renal function before the change of morphology at the early stage of obstructive nephropathy revealed by DCE MRI.