Effects Of Unilateral Partial Ureteral Obstruction On Renal Function And Morphology In Rabbits

Section One: Renal Haemodynamic Changes in Rabbits with Unilateral Partial Ureteral Obstruction in Doppler UltrasonographyObjective: To determine the role of Doppler Ultrasonography in the diagnosis of unilateral obstruction and the prediction of renal function.Methods: Forty-five rabbits were involved in the study. Ten were selected at random as controls before operation. Among the 45 rabbits, 40 were assigned to four obstruction groups according to different stages (1, 2, 4 and 8 weeks) of unilateral partial ureteral obstruction, with 10 in each group, and the other five rabbits were performed sham-operation. Four weeks later, four rabbits in each obstruction group were removed of the obstruction. The haemodynamic change was recorded and analyzed before operation, after operation and after remove of obstruction with Doppler ultrasonography. The maximum anteroposterior dimension (APD) of renal pelvis, renal cortical thickness (RCT), peak systolic velocity (PSV), end-diastolic velocity (EDV) of the arteries and the resistance index (RI) were measured; the volume of renal pelvis, the delta-RI (changes of RI) and RI ratio were also calculated.Results: The value of APD was 0.27 ± 0.13 and 0.30± 0.07 cm in controls and in sham-operation group respectively, renal pelvic volume was 0.38± 0.27 and 0.41±0.05 cm³, and RCT was 0.41±0.05 and 0.42 ± 0.05 cm respectively, with no significant difference between the two groups (P>0.05). APD was 1.21 ±0.20, 1.69 ±0.20, 2.19 ± 0.32 and 2.35 ± 0.26 cm in the four obstruction group respectively, and the volume of renal pelvis was 3.21±0.7, 6.27±1.75, 9.45 ± 2.74 and 10.72 ± 3.6 cm³ respectively, and both increased significantly after partial obstruction than in controls (P<0.01). While RCT was 0.40 ± 0.06, 0.37±0.07, 0.27±0.04 and 0.27 ± 0.04 at 1, 2, 4 and 8 weeks respectively and decreased only after four weeks post-obstruction (P<0.01). At four weeks after the obstruction was removed, APD and renal pelvis volume were improved notably. But APD value remained significantly higher than in controls when the obstruction time was more than two weeks, and the renal pelvic volume also remained in high level when the obstruction time was more than four weeks (P<0.01). No significant changes in RCT were found after the obstruction was removed.The peak systolic velocity (PSV) of renal artery in control, sham-operation and the four obstruction groups was 39.92 ± 12.27, 38.75 ± 5.46, 37.18 ± 5.22, 29.62±12.44, 29.37 ± 9.06 and 28.22 ± 7.32 cra/s respectively, and there was a significant decrease when the obstruction time ≥ two weeks (P<0.05 or <0.01). PSV of intra-renal artery was 32.35 ± 8.75, 33.01±7.35, 27.32±4.52, 26.52 ± 7.95, 24.00 ± 4.41 and 23.42 ± 5.69 cm/s respectively, which showed a significant decrease when the obstruction time ≥ four weeks (P<0.01). End diastolic velocity (EDV) of renal artery was 21.54 ± 6.83, 22.46 ± 5.33, 16.46 ± 3.82, 13.02 ± 7.33, 12.15 ± 4.00 and 10.20 ± 2.64 cm/s respectively and EDV of intra-renal arteries was 17.55 ± 5.02, 17.77 ± 5.20, 14.04 ± 2.32, 12.06 ± 3.00, 11.12 ± 3.17 and 9.85 ± 2.85 cm/s respectively. The decrease of EDV was more significant than that of PSV as EDV decreased markedly after obstruction for one week (P<0.05 or <0.01). RI of renal artery in the four obstruction groups was increased to 0.55 ± 0.10, 0.58 ± 0.07, 0.58 ± 0.08 and 0.64 ± 0.06 respectively vs 0.46 ± 0.04 in control group and 0.45±0.02 in sham-operation group (all P<0.01). All resistance indices of intra-renal arteries at 2, 4, and 8 weeks after obstruction (0.54 ± 0.05, 0.54 ± 0.07 and 0.58 ±0.05 respectively) was higher than in control (0.45 ± 0.04) and sham-operation group (0.47 ± 0.05) (all P<0.01). Not until four weeks after remove of the obstruction, RI recovered to the level of controls. But the recovery of PSV and EDV seems not remarkable especially in the renal arteries and for the obstruction time≥4 weeks.If we set RI≥0.7, ΔRI≥0.1 and RIR≥1.10 as the criterion for obstruction, the diagnostic accuracy of RI in renal artery was 7.5%, 65% and 80% respectively and in intra-renal arteries was 0, 47.5% and 72.5% respectively.Conclusion: Renal blood flow was significantly slow down after unilateral partial ureteral obstruction and renal haemodynamic changes could reflect the functional status of kidney. The resistive index is a time-dependent physiological parameter, it reflects the morphological and functional change following obstruction. Comparison of RI with the contralateral is helpful for the diagnosis of obstruction.Section two Evaluation on Function of Obstructive Kidney by Perfusion Imaging with Multi-slice Spiral CTObjective: To investigate the diagnostic value for hydronephrotic kidney by perfusion imaging with multi-slice spiral CT (MSCT), and to compare the results with those of Doppler Ultrasonography.Methods: Ten adult health rabbits were examined with kidney perfusion imaging with MSCT and color Doppler flow imaging (CDFI) before and four weeks after inducing right ureteral partial obstruction. The dose of contrast agent was 2 ml/kg at 1 ml/s. Results: Renal perfusion imaging with MSCT indicated pelviectasis and cortex thinned at four weeks after obstruction, the cortical and medullary blood flow was slow down significantly from 892.58 ± 62.74 and 192.24 ±96.48(ml/100g/min), respectively, of baseline to 467.66 ± 111.27 and 14.84 ± 7.62 (ml/100g/min) respectively(P<0.01); the blood volume was decreased from 21.70±10.32 and 8.48±4.68, respectively, of baseline to 12.17 ± 2.34 and 4.07 ± 5.29 (rnl/100g/min) respectively (P<0.01 or<0.05). But the mean transit time (MTT) of contrast had no change. The cortical permeability surface (PS) descended and there was no significant difference before and after the obstruction, But the medullary PS was markedly decreased from 94.04±18.70 to 30.66 ± 18.46 (ml/100g/min).CDFI results indicated PSV and EDV, regardless of renal or intra-renal artery, significantly decreased after obstruction as compared with baseline (P<0.01). PSV decreased from 37.76 ± 9.86 and 33.57 ± 7.16 cm/s respectively in renal and intra-renal arteries to 29.37 ± 9.06 and 24.00±4.41 cm/s respectively. EDV dropped from 20.54 ± 4.70 and 17.97 ± 3.32cm/s respectively to 12.15 ± 4.00 and 11.12±3.17cm/s. On the contrary, RI was increased markedly after obstruction as compared with baseline (P<0.01), and it stepped up from 0.45 ± 0.03 and 0.46 ± 0.04 respectively to 0.58 ± 0.08 and 0.54 ±0.07.Conclusion: Renal perfusion imaging with MSCT can reflect the blood flow through kidney in unit time and blood capillary amount in work. Thus it can be used to reflect the glomerular filtration rate (GFR). The parameters from MSCT were consistent with those of CDFI, which can be applied to evaluate the function of kidney. Section three ^99mTc-DTPA Renal Dynamic Imaging in Judgment of the Recoverable Function in Partial Obstructive RabbitsObjective: To evaluate ^99mTc-DTPA renal dynamic imaging in the diagnosis of the renal function in unilateral partial obstructive rabbits, so as to analyze the predictive value of GFR for the functional restoration, and to provide reference for clinical treatment. Methods: Thirty adult healthy rabbits were assigned into control group (n=3), sham-operation group (n=3) and four obstructive groups (n=6 in each) randomly. The four obstructive groups were performed with unilateral paitial ureteral obstruction and maintained obstruction for 1, 2, 4, and 8 weeks respectively, and three rabbits in each group were removed of obstruction and observed four weeks later. GFR, T_b and T_1/2 were measured or calculated with ^99mTc-DTPA renal dynamic imaging techniques. Results: GFR decreased gradually after unilateral partial ureter obstruction, but the serum BUN and Cr maintained in normal level. GFR at 1, 2, 4 and 8 weeks following obstruction was 29.25 ± 5.57, 27.15 ± 7.20, 25.30±8.05 and 21.32 ± 4.10 ml/min respectively, and all were lower than controls (60.60 ± 8.14 ml/min) and sham-operation group(59.09 ± 6.04 ml/min) (all P<0.01). After the animals were free from obstruction for four weeks, the GFRs of both kidneys increased slightly. GFR of the obstructive kidney increased from 26.40 ± 2.94, 22.57 ± 7.51, 18.97 ± 4.91 and 21.93 ± 3.17 ml/min respectively in the four obstructive group to 28.37±5.68, 25.13 ± 5.56, 20.77 ± 2.02 and 21.27 ± 5.59 ml/min respectively. No changes were found after the obstruction was free (P>0.05). With GFR>10 ml/min as a criterion, two third of the obstructive kidneys recovered in certain degree at four weeks after release.Conclusion: GFR decreased at early stage after partial ureter obstruction and recovered slowly after the obstruction was removed for four weeks or longer. When GFR of obstructive kidney was more than 10 ml/min, it is more easily for the recovery of renal function. Section four Immunohistochemistry Study on the Expressin of Angll, AT₁R, AT₂R and TGF-β₁ in the Obstructive Renal TissueObjective: To assay the angiotensin-convertion enzyme (ACE) level in renal venous blood in unilateral partial ureter obstruction rabbits, to study the expression of AngII, AT₁R, AT₂R, TGF-β₁ and collagen protein in obstructive renal tissue, and to analyze their relationship with tubulointerstitial fibrosis in order to provide an possible way to reverse the fibrotic process in the future.Methods: The serum ACE level of experimental rabbits of Section Three was measured with Abbott Aeroset autoanalyzer (USA), the kidney was imbedded by paraffin for HE, Masson collogen staining and immunohistochemistry analysis. Image analysis technique was applied for determining the average optical level of the expressed protein.Results: The serum ACE level was 49.67 ± 4.51, 52.00 ± 5.30, 98.67 ± 20.21 and 38.00 ± 10.15 U/L in the four obstruction groups (1, 2, 4 and 8 weeks respectively after unilateral partial ureteral obstruction). While in the normal control and sham-operation control group was 34.67 ± 6.66 and 39.00±2.65U/L respectively, and there was significant differences between 2 or 4 weeks obstruction group and the controls (P<0.05 or<0.01). After the release of obstruction, no differences between obstructive groups and controls could be found.The pathohistological observation showed that renal tubules were distended and oedema was found in epithelium after obstruction for one week, and fibroplasia in renal medullary and lymph cell infiltrating were found at two weeks after obstruction. When the obstruction time was more than four weeks, the renal tubules become cystic and some of them were atrophy, tubulointerstitial fibrosis were more and more severe by end of eight weeks obstruction, and the glomerulus and tubules atrophy appeared. These pathological changes were not improved well after the obstruction released.The positive expression of collogen protein was mainly in interstitial cells and increased according the obstruction time. The average optical level was 0.2969 ± 0.04, 0.3390 ± 0.02, 0.3424±0.04 and 0.3411 ±0.02 respectively in 1, 2, 4 and 8 weeks obstruction group vs 0.2995 ± 0.02 in the normal control, with a significant increase after two weeks of obstruction (all P<0.01), there was no difference in expression between the cortical and medullary in each group (all P>0.05).Immohistochemistry analysis of obstructive kidney showed that the expression of AngII was consistent to that of AT₁R, which increased progressively during the experiment. The average optical level of AngII was 0.3871±0.02, 0 4046 ± 0.02, 0.4352 ± 0.03 and 0.4297 ± 0.02 respectively in the four obstructive groups, and that of AT₁R was 0.3974 ± 0.02, 0.4240 ± 0.03, 0.4383 ± 0.03 and 0.4282 ± 0.03 respectively. The two values in control group was 0.3851±0.01 and 0.3984 ± 0.02 respectively, so there was significantly increases after 2 weeks obstruction ( all P<0.01). The expression of AT₂R protein were 0.3967 ± 0.03, 0.3940 ± 0.02, 0.4160 ± 0.02, 0.4061±0.02 respectively in each obstructive group and 0.3981 ±0.02 in control, with no significant difference among them (P>0.05). The, positive TGF-β₁ was also mainly in interstitial cells, the expressive level were 0.4083 ± 0.03, 0.4214 ± 0.03, 0.4157 ± 0.03 and 0.4281 ± 0.02 respectively in the four groups and 0.4060 ± 0.03 in the control, which showed an increase only between in 8 weeks obstruction and control group(P<0.01). Conclusion: The pathological change of kidney was interstitial fibrosis in partial ureter obstruction rabbits, and the fibrotic degree was progressively severe with time. There was a close relationship between the activation of rennin-angiotensin system (RAS) and renal interstitial fibrosis, and RAS may be a motivate factor of injury, which up-regulates the expression of TGF-β₁ and contribute to the fibrosis of the obstructive kidney.