Dynamic Enhanced MR Study On Changes Of Renal Function Before And After Recanalization Of Unilateral Ureteral Obstruction In Rabbits

Objective: To establish a rabbit model of unilateral ureteral obstruction by using IVM occluder,and to observe the recovery of renal function before and after recanalization of unilateral ureteral obstruction in different time groups by dynamic enhanced MR,so as to explore the latest time point of relieving obstruction with clinical significance.Methods: 50 female New Zealand white rabbits with a body weight of 3-3.5 kg bred by Tianjin Yuda Laboratory Animal Breeding Company were used to establish animal models.They were fed at room temperature to ensure adequate drinking water and regular and quantitative feed supply.All the animals were randomly divided into 5 groups,10 in each group: sham operation was performed in the control group,and recanalization model of right upper urinary tract obstruction was established in the other 4 groups.Ureteral recanalization was performed on the 3rd,7th,14 th and 28 th day after obstruction.Dynamic enhanced MR was performed before recanalization and 1 month after operation.The equipment was 1.5T nuclear magnetic resonance scanner(Archiva,Philips,Netherlands).Eight-channel phased array coils(aperture 20cm)were used for localization scanning.After routine sequence scanning,Gd-DTPA(Gd-DTPA 0.04 mmol/kg)was injected manually from rabbit ear vein.The flow rate was 1.0 ml/s and 2 ml 0.9% sodium chloride solution was used for flushing.High Resolution Isotropic Volume Exchange(THRIVE)technique was used in dynamic enhanced scanning.Coronal double kidney scanning was performed.Scanning parameters TR: 245 ms,TE: 10 ms,NSA: 1,matrix: 256 *256,FOV: 130 mm,layer thickness: 3 mm,three layers,each acquisition time was 4.0 s,a total of 30 consecutive periods.Using Philips EWS(Extended MR Workspace,R3.2.3,Netherlands)workstation and T1-PERFUSSION software,the contours of the cortex and medulla of interest on the median coronal image were depicted respectively.The time signal intensity curve was automatically generated by the software,and the glomerular filtration coefficient was calculated according to Baumann-Rudin model.Configuration of 21 different concentrations of contrast medium saline mixed solution: 0.25 mmol/L,0.5 mmol/L,0.5 mmol/L,0.75 mmol/L,1.0 mmol/L,1.25 mmol/L,1.25 mmol/L,1.25 mmol/L,1.75 mmol/L,2.0 mmol/L,2.25 mmol/L,2.5 mmol/L,2.5 mmol/L,2.75 mmol/L,2.75 mmol/L,3.3.0 mmol/L,3.3.5 mmol/L,3.3.25 mmol/L,35 mmol/L,35 mmol/L,3.3.75 mmol/L,3.75 mmol/L,3.75 mmol/L,3.75 mmol/L,3 75 mmol 5.0 mmol/L,0 mmol/L.They were placed in 10 ml plastic pipes,fixed with a holed plastic frame and heated to 37 C in a water bath.After positioning scanning with 8 channels of high resolution head coil,the model was scanned cross-sectionally.Scanning sequence: T1-IR;parameters: TR: 498 ms,TE: 15 ms,IR delay: 400 ms,NSA: 2,matrix: 256 *256,FOV: 150 mm *150mm,thickness: 4mm.It was verified that in vitro Gd-DTPA was linearly correlated with relative signal intensity in the concentration range of 0-5.0 mmol/L.SPSS 19.0(SPSS Inc.,Chicago,IL)statistical software was used for variance analysis,independent sample t test between groups,paired sample t test before and after RUUO.The data showed that P < 0.05 had significant difference.Result: Compared with the control group,the KCl of the affected kidney decreased significantly at 3 days after UUUO operation(P < 0.05);it decreased slowly at 3 days after UUUO operation(P > 0.05)at 7 days and 14 days(P > 0.05);it decreased again at 28 days(P < 0.05)compared with 14 days(P < 0.05).The KCl of RUUUO in 3 days,7 days and 14 days group recovered significantly at 1 month after operation(P < 0.05).Conclusion: 1.Dynamic contrast-enhanced MR can reflect the changes of renal function in obstructive nephropathy;2.Removal time of obstruction is an important factor affecting the recovery of renal function;3.Removal of obstruction up to 28 days is of no clinical significance.