Partial Ureteropelvic Junction Obstruction Research Articles

Hydronephrosis and risk of later development of hypertension.

Congenital ureteral obstruction is a fairly common condition in infants, and its clinical management has been long debated during the last decade. The long-term physiological consequences of today's conservative non-surgical management in many asymptomatic hydronephrotic children are unclear. Experimental studies in rats and mice, retrospective studies in children and adults, as well as prospective studies in children are included in this mini review. Experimental models of hydronephrosis in rats and mice have demonstrated that partial ureteropelvic junction obstruction (UPJO) is casually linked with development of hypertension and renal injuries in later life. The mechanisms are multifactorial and involve increased activity of the renin-angiotensin-aldosterone system and renal sympathetic nerve activity. Furthermore, oxidative stress and nitric oxide deficiency in the affected kidney appear to play important roles in the development and maintenance of hypertension. Clinical case reports in adults and recent prospective studies in children have associated hydronephrosis with elevated blood pressure, which could be reduced by surgical management of the obstruction. Based on current experimental and clinical knowledge regarding the link between partial UPJO and changes in blood pressure, it is proposed that today's non-operative management of hydronephrosis should be reconsidered to reduce the risk of developing elevated blood pressure or hypertension in later life.

Incidence and implications of silent hydronephrosis following percutaneous nephrolithotomy

While routine renal imaging following ureteroscopy for urinary calculi has been recommended to screen for asymptomatic "silent" obstruction, the rate of silent obstruction following percutaneous nephrolithotomy (PCNL) remains poorly defined, and no consensus recommendations exist on routine postoperative imaging. At our institution, we sought to assess the incidence of silent hydronephrosis (SH), as a screen for obstruction, following PCNL. The records of all 162 patients who met study inclusion criteria were reviewed. Of this group, 112 patients presented for their scheduled renal ultrasonography 4 - 6 weeks following stent removal to screen for SH. Asymptomatic patients found to have ultrasonographic evidence of hydronephrosis were further analyzed. SH was noted in 16% (18/112) of patients. Two required subsequent ureteroscopic stone extraction (1.8%), one of which also underwent endoureterotomy for a ureteral stricture. Four patients (22%) had stable hydronephrosis and declined functional imaging, 2 patients (11%) had a known partial ureteropelvic junction obstruction and declined intervention. SH resolved spontaneously in 50% (9/18) with a mean time to resolution of 6.3 months. There was no difference in stone complexity based on Guy's stone score between groups, 2.8 (±0.92) vs. 2.4 (±1.03), p=0.34. Although not statistically significant, patients with SH were more likely to have had residual stone fragments postoperatively, 39% (7/18) vs. 19% (18/94), p=0.067. SH following, PCNL was identified in 16% of this screened population, with the majority requiring no intervention. However, SH may be attributed to residual stone or stricture, which may have been otherwise unrecognized in up to 2% of patients undergoing PCNL. Consideration should be given for routine postoperative ultrasound to screen for silent obstruction following PCNL. .

The effect of alfuzosin on renal resistive index, urinary electrolytes and β2 microglobulin levels and TGF β-1 levels of kidney tissue in rats with unilateral ureteropelvic junction obstruction

Background: In this study, it was aimed to determine the effects of alfuzosin on experimentally generated unilateral partial ureteropelvic junction obstruction (UPO) in rats.Materials and methods: Thirty Long–Evans rats were randomly allocated into five groups. In control group (C), nothing was performed; in group Sham (S) only laparotomy was done; in Alfuzosin group (A) only alfuzosin was administered for two weeks (10 mg/kg/day p.o.) without any surgery; in UPO group, unilateral UP junction obstruction was produced; and in the Group UPT (ureteropelvic obstruction + treatment), alfuzosin was administered for two weeks (10 mg/kg/day p.o.) in addition to UPO production. Renal pelvic anteroposterior diameters were determined with ultrasonography (USG) and renal arterial resistivity indexes by color Doppler USG. Urine was collected both at the beginning and at the end of the experiment for 24 h in all the groups and at the end of the experiment, blood samples were obtained. Blood and urine electrolytes and TGF-β1, urine density, urine β2 microglobulin levels were determined. Renal tissue samples harvested from all of the rats were histopathologically evaluated. Results were determined using one-way ANOVA t-test; p < 0.05 was accepted as significant.Results: Urine density in the UPT group was lower with respect to UPO group and blood electrolytes were preserved as close to normal (p < 0.05). In the UPT group, urine TGF-β1 and blood TGF-β1, blood β2 microglobulin levels and histopathologic damage scores were lower compared to the UPO group (p < 0.05).Conclusion: It is shown in this experimental unilateral partial UPO model that alfuzosin treatment prevents obstructive renal damage.

The Effect of Enalapril on Renal Resistive Index, Urine Electrolyte Levels and TGF-β1 Levels of Kidney Tissues in Rats with Unilateral Partial Ureteropelvic Junction Obstruction

This study aimed to investigate renal arterial resistive index measurements and urine electrolytes before and after enalapril therapy in a rat model of unilateral ureteropelvic obstruction. The transforming growth factor (TGF)-β1 response of the renal tissue was also investigated. 30 Wistar albino rats were randomly allocated into 5 groups (n=6). Group C rats served as controls. Group S rats had only laparotomy. Group E rats were only treated with enalapril. Rats in group UP and group UPE underwent laparotomy to create a left unilateral moderate partial obstruction. 2 weeks after establishing partial ureteropelvic junction obstruction, group UPE rats were treated with enalapril. Urine was collected over 24 h in all groups. Intrarenal arterial resistive index measurements were performed before and 2 weeks after surgery and after enalapril treatment in group UPE, and before and after enalapril treatment in group E. Rats were sacrificed by intracardiac puncture and left kidneys were harvested to evaluate levels of mRNA TGF-β1. There was no significant difference in ARI values in group E. In group UPE, the difference between ARI values before and after surgery was statistically significant; the difference between ARI values after surgery and after enalapril treatment was also statistically significant. There was no statistically significant intra-group difference in urine electrolyte levels for UP group or UPE group. There was no difference in renal mRNA TGF-β1 levels. Enalapril maintained renal blood flow by decreasing the arterial resistive index and maintained renal tubular function by protecting urine concentration and dilution ability in a rat model with unilateral ureteropelvic junction obstruction.

Ureteropelvic junction obstruction causes histologic alterations in contralateral kidney

Background/Purpose: Ureteropelvic junction (UPJ) obstruction causes histologic alterations both in ipsilateral and contralateral kidney. Because these alterations directly affect the fate of renal damage, definition of these alterations is of utmost importance from the clinical point of view. Thus, an experimental study is designed to determine the alterations of renal histology in response to partial and complete UPJ obstruction. Methods: Fifteen adult female New Zealand rabbits were assigned randomly into 3 groups (each containing 5 rabbits) according to the degree of unilateral UPJ obstruction as group I, sham operation was performed and served as the control group; group II, partial UPJ obstruction was made; group III, complete UPJ obstruction was made. The animals in group I and II were killed after 3 weeks, and animals in group III were killed after 2 weeks. Tissue samples were prepared and processed according to routine light microscopic tissue processing. Results: UPJ obstruction led to glomerulosclerosis, dilatation of proximal and distal tubules of loops of Henle, and dilatation of collecting tubes consistent with necrotic and apoptotic changes in ipsilateral kidneys. Severity of these degenerative changes depended on degree of obstruction. UPJ obstruction also led to histologic alterations on the contralateral kidneys such as glomerular edema, congested blood vessels, dilated tubuli, and necrotic and apoptotic changes in epithelia, which were more prominent in group III than group II. Conclusions: It is well known that compensating changes including increased blood flow and parenchymal hypertrophy occurs in contralateral kidney as a response to unilateral UPJ obstruction. However histologic findings of this study confirmed progression of parenchymal damage and presence of apoptosis in contralateral kidney for the first time.

PARTIAL UNILATERAL URETEROPELVIC JUNCTION OBSTRUCTION INDUCED IN 2-WEEK-OLD PIGLETS

We examined effects on kidney function and morphology of a partial ureteropelvic junction obstruction induced late in the postnatal nephrogenesis period of the pig. We compared the results to a similar study on pigs with obstruction induced early in the nephrogenesis period. A total of 20 14-day-old pigs were included in the study. Fifteen animals were randomized to partial unilateral obstruction and 5 were sham operated. Kidney function and morphology were analyzed regarding glomerular filtration rate, renographic functional share and total kidney volume at the age of 4, 12 and 24 weeks. At age 4 weeks hydronephrosis was found in all obstructed kidneys included in the study. Four obstructed kidneys had renographic functional share 40% or greater and 1 deteriorated to less than 40% at 24 weeks. A total of 11 obstructed kidneys had a functional share less than 40%, 5 increased to a share greater than 40% at age 24 weeks and 3 had decreasing share from age 4 to 24 weeks. Single kidney glomerular filtration rate of the contralateral kidneys was significantly increased at all ages. Volume of the contralateral kidney was significantly increased at age 4 and 12 weeks. The variability and course of renographic functional share in kidneys subjected to partial obstruction at age 2 weeks was similar to findings obtained in pigs obstructed at age 2 days. In contrast to these our study showed compensatory increase in function and size of the contralateral kidney, suggesting that contralateral compensation is an ability gained late in the nephrogenesis period.

Use of ureteral stents in the management of major renal trauma with urinary extravasation: is there a role?

Five patients with major (Grade IV) renal trauma required ureteral stent placement to facilitate urinary drainage. Three of these patients had stents placed for recurrent gross hematuria with flank pain. All three had obstructing blood clots present at the time of stent placement. The fourth patient had a stent placed because of persistent extravasation at 2 weeks postinjury. The last patient was considered at risk for persistent urinary extravasation because of a partial ureteropelvic junction obstruction and had a ureteral stent placed as part of the initial management. All patients were followed radiographically for resolution of extravasation. Long-term clinical follow-up consisted of serum creatinine evaluation and blood pressure monitoring. Urinary extravasation resolved in all five patients, as determined by radiologic evaluation, at a mean of 8 days after stent placement. Ureteral stents were left indwelling an average of 4 weeks. No patient developed hypertension, and all serum creatinine values were normal at a mean 26 months' follow-up. No patient developed urinoma or abscess, and none required open surgical exploration. Ureteral stents may be used safely and effectively to treat persistent or recurrent urinary extravasation resulting from major blunt renal trauma in appropriately selected patients. In addition, ureteral stents may avoid the need for surgical exploration in patients with Grade IV renal trauma who develop recurrent gross hematuria, flank pain, and persistent or recurrent extravasation secondary to clot obstruction.

Intrapelvic pressure monitoring in the partially obstructed porcine kidney

Objectives. The diagnosis of urinary obstruction in newborns and infants remains difficult because the diagnostic studies available at present are fraught with many problems. It is our premise that precise measurement of renal pelvic pressures under physiologic conditions in patients with urinary tract dilation will allow diagnosis of obstruction and prediction of further renal damage. This study evaluates an intrapelvic pressure monitoring system. Methods. Four porcine subjects had partial ureteropelvic junction obstruction createdsurgically; two subjects were used as controls. Doppler ultrasound and MAG-3 furosemide renography were performed preoperatively and each week pressures were measured with a Millar 5 F solid-state pressure transducer and the analog signals were converted on line to digital information to allow signal processing and later data analysis. Antegrade nephrostograms were obtained at the same sitting and showed that the model remained stable over time. Measurements were obtained at physiologic flow rates as well as at the standard Whitaker infusion rate of 10 cc/min. Results. Thirteen pressure studies were performed on 9 kidneys. Each study was classifiedas normal (4), partial obstruction (8), or total obstruction (1), based on ultrasound and nephrostogram criteria. The normal units had baseline pressures of 4.12±0.94 cm water (H 2O), which increased to 9.12 ± 1.38 cm H 2O with infusion. In the partially obstructed group, baseline was 16.4±3.83 cm H 2O and increased to 35.3 ± 15.9 cm H 2O with infusion. The kidney with total obstruction showed a baseline pressure of 27 cm H 2O, which increased to 68 cm H 2O with infusion. These pressure measurements were also compared to furosemide renography. Conclusions. Intrapelvic pressures correlated well with conventional ultrasound andnephrostogram in the evaluation of partial obstruction. However, the results of furosemide renography and the Whitaker test were quite variable and did not accurately define partial obstruction or correlate with intrapelvic pressure. The Millar solid-state transducer monitoring system is an accurate method of evaluating the intrapelvic pressure and could possibly become a standard for diagnosing significant urinary obstruction against which other studies can be evaluated.

Ultrafast Contrast Enhanced Magnetic Resonance Imaging of Congenital Hydronephrosis in a Rat Model

Since new ultrafast magnetic resonance imaging (MRI) might offer unique advantages for evaluating renal blood flow, anatomy and urinary excretion, we used this technique to characterize a rat model with congenital partial ureteropelvic junction obstruction. MRI of 9 rats from an inbred colony with unilateral congenital (nonsurgical) hydronephrosis was compared with the contralateral nonhydronephrotic kidney serving as control. Our new imaging technique consisted of a 1-minute ultrafast gradient recalled imaging sequence during the first minute (64 images per imaging time 960 milliseconds) after contrast bolus injection with gadolinium-diethylenetri-aminepentaacetic acid for assessment of renal blood flow followed by a 30-minute period with image acquisition every 30seconds to study contrast distribution and excretion. Signal intensities were analyzed continuously over selected, different regions of interest. Anatomic analysis of MRI noncontrast studies showed precise delineation of the hydronephrotic pelvis and cortico-medullary junction. After contrast gadolinium-diethylenetriaminepentaacetic acid injection signal intensity from the region of interest from hydronephrotic kidneys differed from nonhydronephrotic kidneys by showing less cortical decrease, suggesting decreased blood flow, less medullary decrease and delayed contrast excretion. Clear contrast distribution among the cortex, medulla and collecting system allowed selective estimation of different regions of interest and excellent anatomic evaluation. Renal anatomy and renal pelvic pressures were confirmed after scans were completed.Ultrafast contrast enhanced MRI allows simultaneous assessment of renal morphology, blood flow and function. In hydronephrotic partially obstructed kidneys distinct flow and excretion patterns measured with contrast enhanced MRI allow differentiation between the obstructed and nonobstructed kidney on physiological rather than purely anatomic means. This imaging technique may provide a useful method of evaluating congenital hydronephrosis obviating the need for multiple different diagnostic procedures.

Determinants of progression and equilibrium in hydronephrosis

Upper urinary tract urodynamic parameters were measured serially in 12 dogs subjected to partial ureteropelvic junction obstruction. Measurements of pressure-volume relationships (pelvimetrics) and the physiologic capacity of the renal pelvis were important predictors of hydronephrotic equilibrium which occurred only in kidneys whose pelvic urine volume remained lower than the renal pelvic capacity. Because of acquired changes in compliance and renal function, the same degree of obstruction caused progressive hydronephrosis at low pelvic volumes but not at high volumes in some kidneys. Hydronephrosis can thus be viewed as a compensatory mechanism which protects the kidney against further dilation and elevated intrapelvic pressure.