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ORIGINAL ARTICLE
Year : 2012  |  Volume : 17  |  Issue : 2  |  Page : 49-53
 

Unilateral ureteric obstruction: Role of renin angiotensin system blockade on renal recovery: An experimental study


1 Department of Pediatric Surgery, All India Institute of Medical Sciences, New Delhi, India
2 Department of Pathology, All India Institute of Medical Sciences, New Delhi, India

Date of Web Publication17-Mar-2012

Correspondence Address:
Minu Bajpai
Department of Pediatric Surgery, All India Institute of Medical Sciences, New Delhi
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0971-9261.93960

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   Abstract 

Aims: To study and compare the effects of angiotensin II antagonist (Losartan) and angiotensin converting enzyme (ACE) inhibitor (Enalapril) on renal recovery following reversal of iatrogenic unilateral upper ureteric obstruction. Materials and Methods: Unilateral upper ureteric obstruction was created in 96 adult Wistar rats that were reversed after predetermined intervals. Losartan and Enalapril were given to different subgroups of rats following relief of obstruction. Rats were sacrificed and kidneys were subjected to planimetric and histopathological analysis. Results: Dorsal lumbotomy approach provided a rapid and safe approach to kidneys in rats. The planimetric and histopathological changes were most severe in the group of rats in whom obstruction was not relieved before sacrifice. Addition of Enalapril and Losartan significantly hastened the reversal of renal changes following relief of obstruction as compared with the group in which no treatment was given following reversal of blockade. Conclusions: Renin angiotensin system (RAS) is the major pathway responsible for renal damage following outflow obstruction. However, this damage can be reversed with the use of drugs acting on the RAS.


Keywords: Hydronephrosis, renin angiotensin system, ureteric obstruction


How to cite this article:
Sinha A, Bajpai M, Panda S, Ranjan S, Sharma MC. Unilateral ureteric obstruction: Role of renin angiotensin system blockade on renal recovery: An experimental study. J Indian Assoc Pediatr Surg 2012;17:49-53

How to cite this URL:
Sinha A, Bajpai M, Panda S, Ranjan S, Sharma MC. Unilateral ureteric obstruction: Role of renin angiotensin system blockade on renal recovery: An experimental study. J Indian Assoc Pediatr Surg [serial online] 2012 [cited 2018 Jan 22];17:49-53. Available from: http://www.jiaps.com/text.asp?2012/17/2/49/93960



   Introduction Top


The diagnosis and management of pelvi-ureteric junction obstruction (PUJO) has always been a matter of debate among the pediatric surgeons. The matter is complicated by two issues; first, there is no single test available that can differentiate the nonobstructive hydronephrosis from the obstructive ones and second, there is a dilemma to treat asymptomatic hydronephrosis, as many of them would resolve on their own. [1],[2],[3]

We have reported the activation of the renin angiotensin system (RAS) early in congenital uropathies, [4],[5],[6] suggesting that renin can act as the discriminatory factor between pathological and nonpathological obstruction. The pathophysiology of congenital obstructive uropathy has been studied in animal models. [7],[8],[9]

While even bilateral neonatal hydronephrosis can be managed conservatively without much discernible loss of function, [10] the long-term safety of this approach needs to be established.

The present study was conducted to study the role of the RAS in the pathological effects of renal outflow obstruction.


   Aims and Objectives Top


This work was initiated with the aim to study the effect of RAS blockade on pathological changes in experimentally created unilateral ureteric obstruction and its reversal in rat kidneys.


   Materials and Methods Top


This prospective study was performed at the Department of Pediatric Surgery and Central Animal Facility at All India Institute of Medical Science, New Delhi, after obtaining permission from the institute's animal ethics committee for study on adult female Wistar rats (weighing 100-150 g).

The rats were divided into four groups of 30 rats each. The left ureter was ligated in each rat. The groups were further subdivided into subgroups of 10 rats, depending on the duration for which the ureters were obstructed (7, 21 and 42 days, respectively). Group I acted as control to study the renal changes on creating a proximal ureteric obstruction. The rats were sacrificed at the end of 7, 14 and 21 days. Group II served to study the reversal of these changes upon relieving this obstruction. The ureteric obstruction was relieved at the end of 7, 21 and 42 days and the rats were then sacrificed 14 days following the reversal. Group III was used to demonstrate the benefit of adding an angiotensin receptor blocker Losartan during the recovery phase. Losartan was given at a dose of 1 mg/kg/day for 14 days following reversal of obstruction and the rats were then sacrificed. Group IV was similar to Group III, except for the use of Enalapril at a dose of 50 mg/kg/day instead of Losartan.

The rats were anesthetized using 50 mg/kg Ketamine, administered intraperitoneally using a 26 guage needle. A dorsal lumbotomy incision (described previously [11],[12],[13] ) was given on the left side. The proximal ureter was tied with a flexible camera cover wire. This wire was then hitched to the psoas and the edges brought out through the incision's corner. Five milliliter of normal saline was instilled intraperitoneally to account for the losses during the procedure.

The projecting ends of the wire made it easy to determine the site of previously created obstruction. It thus reduced the incision required in the second sitting and reduced the time required for the procedure, and hence the anaesthetic dose required. The wire was untwisted and removed and the ureter reposited back to relieve the obstruction.

The rats were sacrificed using Thiopental sodium intraperitoneally at a dose of 20 mg/kg. A postmortem midline vertical laparotomy was done to retrieve the kidneys.

Morphometric Measurements

The kidneys were split longitudinally and photographed along with a scale, using a 12.1 megapixels 4x optical zoom digital camera kept vertically overhead at a distance of 25 cm and at an angle of 15 degree. The various dimensions, viz. the renal height, pelvic dimensions (antero-posterior, craniocaudal and lateral) and renal cortical thickness at the upper and lower pole was measured with a least count of 0.01 mm using the I-photo-measure software version 3.0 [Figure 1].
Figure 1: Measurements on I photomeasure software

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Pathological Grades

The slides were stained with hematoxylin and eosin and Masson's trichrome stains. The distances were measured with Image Pro Plus software with a least count of 0.00001 μm. The pathological grades were as shown in [Table 1], [Table 2], [Table 3] and [Table 4].
Table 1: Grade of renal parenchymal damage

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Table 2: Grade of fibrosis at pelvi-ureteric junction

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Table 3: Hypertrophy at upper ureter

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Table 4: Inflammation at PUJ lamina propria

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The data analysis was done using STATA software version 9.0 Stata Corp LP, TX, USA. The continuous data were compared using t-test and dichomatous data were compared using Chi square test. A P -value of <0.05 was considered statistically significant.

Observations

The study included a total of 96 rats, 24 in each group and eight rats for each subgroup based on duration. (Please see section on Materials and Methods description of groups.)

Morphometric Analysis

The average renal height in the various groups and with various durations of obstruction in Group I was

21.3 mm at 7 days, 23.2 mm at 21 days and 24.8 mm at 42 days. In Group II, it was 20.6 mm at 7 days, 21.8 mm at 21 days and 23.9 mm at 42 days. In Group III, it was 20.5 mm at 7 days, 20.8 mm at 21 days and 21.6 mm at 42 days. The average renal height in Group IV was 19.9 mm at 7 days, 20.9 mm at 21 days and 22.2 mm at 42 days.

Cranio-Caudal, Antero-Posterior and Lateral Dimensions of the Pelvis (Antero-Posterior Diameter x Lateral Diameter x Cranio-Caudal Diameter)

The overall pelvic volume in Group I was 354.5 mm 3 at 7 days, 349.5 mm 3 at 21 days and 490.0 mm 3 at 42 days. In Group II, it was 200.0 mm 3 at 7 days, 286.5 mm 3 at 21 days and 481.0 mm 3 at 42 days. In Group III, it was 229.1 mm 3 at 7 days, 242.9 mm 3 at 21 days and 252.3 mm 3 at 42 days. In Group IV, it was 215.4 mm 3 at 7 days, 223.7 mm 3 at 21 days and 280.2 mm 3 at 42 days.

At 42 days, there was a significant difference in the pelvic volumes between Group I and Group III (P < 0.0001) and Group I and Group IV (P < 0.0001).

Average cortical thickness: Renal height

In Group I, it was 0.151 at 7 days, 0.139 at 21 days and 0.121 at 42 days. In Group II, it was 0.162 at 7 days, 0.147 at 21 days and 0.125 at 42 days. In Group III, it was 0.159 at 7 days, 0.151 at 21 days and 0.147 at 42 days. In Group IV, it was 0.160 at 7 days, 0.149 at 21 days and 0.141 at 42 days.

Pathological Analysis

The parenchymal damage was graded from I to IV, with duration of obstruction at Day 7, Day 21 and Day 42 [Figure 2].
Figure 2: Pathological changes seen at the end of 42 days of obstruction (H and E, ×20)

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At 42 days in Group I, Grade IV was present in 8. In Group II, Grade III was present in 3 and Grade IV was present in 5. In Group III, Grade II was present in 1, Grade III was present in 4 and Grade IV was present

in 3. In Group IV, Grade II was present in 1, Grade III was present in 5 and Grade IV was present in 2.

Fibrosis at Pelvi-Ureteric Junction

The fibrosis at PUJ was also graded from I to IV, with duration of obstruction at Day 7, Day 21 and Day 42.

At 42 days in Group I, Grade IV was present in 8. In Group II, Grade III was present in 2 and Grade IV was present in 6. In Group III, Grade II was present in 2, Grade III was present in 5 and Grade IV was present in 1. In Group IV, Grade II was present in 1, Grade III was present in 6 and Grade IV was present in 1.

Ureteric muscular hypertrophy

The ureteric muscular hypertrophy, as in the ratio of ureteric muscle to the total wall thickness, was graded from I to III, with duration of obstruction at Day 7, Day 21 and Day 42.

At 7 days in Group I, Grade II was present in 3 and Grade III was present in 5. In Group II, Grade II was present in 4 and Grade III was present in 4. In Group III, Grade I was present in 2, Grade II was present in 4 and Grade III was present in 2. In Group IV, Grade I was present in 2 and Grade III was present in 6.

At 21 days in Group I, Grade III was present in 8. In Group II, Grade II was present in 4 and Grade III was present in 4. In Group III, Grade II was present in 3 and Grade II was present in 5. In Group IV, Grade I was present in 2, Grade II was present in 3 and Grade III was present in 3.

At 42 days in Group I, Grade III was present in 8. In Group II, Grade II was present in 1 and Grade III was present in 7. In Group III, Grade II was present in 2 and Grade III was present in 6. In Group IV, Grade I was present in 1, Grade II was present in 6 and Grade III was present in 1.


   Discussion Top


Children with an antenatal diagnosis of PUJ obstruction reportedly show a significant improvement in renal function after surgery compared with those who are diagnosed and operated much later because of their clinical symptoms. [14] It is still not clear as to which kidneys will recover following surgery and which kidneys would do well without any intervention.

Histopathological changes vary with degree and duration of obstruction in various studies. [15],[16]

The pathogenesis of renal damage has been extensively studied. An intact RAS is an important determinant in the normal development of kidneys and the urinary tract. [17]

In the present study, when renal height measurement were analyzed, it was found that the difference between Groups I and II was not significant, indicating that simply reversing the obstruction did not bring about a significant change but adding angiotensin converting enzyme inhibitors or angiotensin II blockade had an effect in reversing the degree of increase in renal height significantly. However, there was no difference in changes between the two groups, viz. Losartan (group III) and Enalapril (group IV) (P = 1.00).

When comparisons were drawn on the basis of groups, there was significant difference between days 7 and 21 and 7 and 42 in Group I. There was a similar significant difference between days 7, 21 and 42 in Group II. However, in Groups III and IV, there was no significant difference at various durations. This signifies that the drugs have been able to revert back the significant increase in renal height caused due to increase in duration of obstruction.

The pelvic volumes were significantly different between Group I and the other groups at 7 days. This signifies that if the obstruction is reversed early, the degree of hydronephrosis comes back to normal. There was no difference between Group II and Groups III and IV. This is probably because if the obstruction is relieved, the hydronephrosis reverts back to normal even without drugs.

Our clinical observations alone (under publication) on renal pelvic volumes have revealed a better correlation with progression of hydronephrosis than measuring AP diameter of renal pelvis. Those observations formed the basis of this experimental study.

At 42 days, there was a significant difference in the pelvic volumes between Group I and Group III (P < 0.0001) and Group I and Group IV (P < 0.0001). The difference between Groups I and II was not significant, indicating that simply reversing the obstruction did not bring about a significant change but adding an anti-renin drug reduced the pelvic volumes significantly. However, there was no difference in this change brought about by Losartan (Group III) and Enalapril (Group IV) (P = 1.00).

When comparisons were drawn on the basis of groups, there was no significant difference between days 7 and 21 and 7 and 42 in Group I. This suggests that hydronephrosis sets in early with obstruction. There was a significant difference between days 7, 21 and 42 in Group II, suggesting that the hydronephrosis does not resolve completely with reversal of obstruction. However, in Groups III and IV, there was no significant difference at various durations. This signifies that the drugs have been able to revert back the hydronephrosis caused due to increase in duration of obstruction.

Observations on cortical thickness between different groups revealed that there was no significant difference between Days 7 and 21 and 7 and 42 in Groups I and II. This suggests that cortical thinning occurs late following ureteric obstruction, which is in contrast to hydronephrosis, which sets in early with obstruction and does not revert following reversal of obstruction. There was no significant difference between Days 7, 21 and 42 in Groups III and IV, suggesting that the cortical thickness returns to normal levels once Losartan or Enalapril is added.

There was no significant difference in the cortical thickness at Day 7 between the groups (P = 0.13) and at Day 21 (P = 0.118). At 42 days, however, there was a significant difference between Groups I and II and Groups III and IV. This signifies that cortical thinning occurs after a prolonged ureteric obstruction, and the changes then are not reversed by reversing the obstruction alone. Adding reno-protective drugs however improves the cortical thickness.

When we compared the cortical thickness and the pelvic volumes, irrespective of the duration of obstruction, we found that there is a significant difference between Groups I, III and IV, suggesting that simply reversing the obstruction does not suffice to revert the morphometric indices and it is the addition of a renoprotective drug, which improves the renal damage.

In the current study, addition of drugs blocking the RAS pathway hastened the recovery of renal parenchymal changes following reversal of obstruction.

Parenchymal thinning occurs after at least 3 weeks of creating the obstruction, and worsens with duration of obstruction. Reversing the obstruction alone does not improve the cortical thickness. Addition of a reno-protective drug however significantly improves the cortical thickness. The pathological changes also vary with duration of obstruction, with long-standing obstruction causing significant and consistent histopathological changes. The reversal of obstruction alone does not result in resolution of this damage, but addition of Losartan or Enalapril results in reversal of these changes. Although there is no significant difference between the two drugs, there appears to be a trend of better recovery in the Enalapril-treated rats.

These observations support our contention [4] that RAS is the major culprit responsible for the functional renal loss in obstructive pathologies as follows:

The renal parenchymal damage occurring in PUJO is secondary to RAS activation. The damage can more effectively be controlled by use of any agent acting on the RAS, as has been demonstrated earlier. [13] Angiotensin-converting enzyme inhibitor (Enalapril) shows a better trend in this regard.

This study supports the earlier observations [4],[18],[19] that early detection of RAS activation can serve to discriminate pathological from nonpathological obstruction. It has recently been demonstrated that use of RAS blockade can retard the pace of clinical renal damage [20] as well as minimise experimentally created damage. [13] The present study further provides proof of mechanism that use of drugs acting on RAS could be useful even in reversing pathological changes caused after a period of experimentally created obstruction.

 
   References Top

1.Witten DM, Myers GH, Utz DC. Emmett's clinical urography: An atlas and textbook of roentgenologic diagnosis. 4 th ed. Philadelphia: Saunders; 1977. p. 986-99.  Back to cited text no. 1
    
2.Koff SA. Neonatal management of unilateral hydronephrosis: Role for delayed intervention. Urol Clin North Am 1998;25:181-6.  Back to cited text no. 2
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3.Disandro MJ, Kogan BA. Neonatal management: Role for early intervention. Urol Clin North Am 1998;25:187-97.  Back to cited text no. 3
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4.Bajpai M, Puri A, Tripathi M, Maini A. Prognostic significance of captopril renography for managing congenital unilateral hydronephrosis. J Urol 2002;168:2158.  Back to cited text no. 4
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5.Bajpai M, Pal K, Bal CS, Gupta AK, Pandey RM. Role of plasma renin activity in the management of primary vesicoureteric reflux: A preliminary report. Kidney Int 2003;64:1643-7.  Back to cited text no. 5
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6.Bajpai M, Bal CS, Kalaivani M, Gupta AK. Plasma renin activity for monitoring vesicoureteric reflux therapy: Mid-term observations. J Pediatr Urol 2008;4:60-4.   Back to cited text no. 6
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7.Chevalier RL, Thornhill BA, Chang AY. Unilateral ureteral obstruction in neonatal rats leads to renal insufficiency in adulthood. Kidney Int 2000;58:1987-95.  Back to cited text no. 7
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8.Peters CA, Carr MC, Lais A, Retik AB, Mandell J. The response of the fetal kidney to obstruction. J Urol 1992;148:503-9.  Back to cited text no. 8
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9.Chevalier RL, Gomez RA, Jones CE. Developmental determinations of recovery after relief of partial ureteral obstruction. Kidney Int 1988;33:775-81.  Back to cited text no. 9
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10.Bajpai M, Chandrasekharam VV. Nonoperative management of neonatal moderate to severe bilateral hydronephrosis. J Urol 2002;167:662-5.   Back to cited text no. 10
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11.Bajpai M, Kumar A, Gupta AK, Pawar DK. Lumbotomy approach for upper urological tract surgery in children--An analysis of 68 consecutive lumbotomies. Eur J Pediatr Surg 2004;14:163-7.  Back to cited text no. 11
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12.Bajpai M, Kumar A, Tripathi M, Bal CS. Dorsal lumbotomy incision in paediatric pyeloplasty. ANZ J Surg 2004;74:491-4.   Back to cited text no. 12
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13.Singal A, Bajpai M, Dinda A. Blockade of Renin-Angiotensin system blunts the fibrotic response in experimental acute pyelonephritis. J Indian Assoc Pediatr Surg 2005;10:20-4.  Back to cited text no. 13
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14.Chertin B, Fridmans A, Knizhnik M, Hadas-Halperin I, Hain D, Farkas A. Does early detection of ureteropelvic junction obstruction improve surgical outcome in terms of renal function? J Urol 1999;162:1037-40.  Back to cited text no. 14
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15.Kim WJ, Yun SJ, Lee TS, Kim CW, Lee HM, Choi H. Collagen to smooth muscle ration helps prediction of prognosis after pyeloplasty. J Urol 2000;163:1271-5.  Back to cited text no. 15
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16.Huang WY, Peters CA, Zurakowski D, Borer JG, Diamond DA, Bauer SB, et al. Renal biopsy in congenital ureteropelvic junction obstruction: Evidence for parenchymal maldevelopment. Kidney Int 2006;69:137-43.  Back to cited text no. 16
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17.Yoo KH, Norwood VF, El-Dahr SS. Regulation of angiotensin II, AT1, and AT2 receptors in neonatal ureteral obstruction. Am J Physiol 1997;273:R503-9.  Back to cited text no. 17
    
18.Bajpai M, Bal CS, Tripathi M, Kalaivani M, Gupta AK. Prenatally diagnosed unilateral hydronephrosis: Prognostic significance of plasma renin activity. J Urol 2007;178:2580-4.  Back to cited text no. 18
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19.Bajpai M, Pratap A, Tripathi M, Bal CS. Posterior urethral valves: Preliminary observations on the significance of plasma Renin activity as a prognostic marker. J Urol 2005;173:592-4.  Back to cited text no. 19
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20.Bajpai M, Bal CS, Kumar R, Chaturvedi PK, Kalaivani M, Gupta AK. Persistent renin-angiotensin system activation after anti-reflux surgery and its management. J Pediatr Urol 2011;7:616-22.  Back to cited text no. 20
[PUBMED]  [FULLTEXT]  


    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]


This article has been cited by
1 Comparison of different morphological parameters with duration of obstruction created experimentally in unilateral upper ureters: An animal model
Panda, S., Bajpai, M., Mallick, S., Sharma, M.
African Journal of Paediatric Surgery. 2014; 11(1): 15-17
[Pubmed]
2 Effect of ipsilateral ureteric obstruction on contralateral kidney and role of renin angiotensin system blockade on renal recovery in experimentally induced unilateral ureteric obstruction
Panda, S.S. and Bajpai, M. and Sinha, A. and Mallick, S. and Sharma, M.C.
Journal of Indian Association of Pediatric Surgeons. 2013; 18(2): 58-61
[Pubmed]



 

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