DOES DELAYED OPERATION FOR PEDIATRIC URETEROPELVIC JUNCTION OBSTRUCTION CAUSE HISTOPATHOLOGICAL CHANGES?

The molecular biology of pelvi-ureteric junction obstruction

Over recent years routine ultrasound scanning has identified increasing numbers of neonates as having hydronephrosis and pelvi-ureteric junction obstruction (PUJO). This patient group presents a diagnostic and management challenge for paediatric nephrologists and urologists. In this review we consider the known molecular mechanisms underpinning PUJO and review the potential of utilising this information to develop novel therapeutics and diagnostic biomarkers to improve the care of children with this disorder.

Serum and urinary procollagen III aminoterminal propeptide as a biomarker of obstructive nephropathy in children

BACKGROUND

Ureteropelvic junction obstruction (UPJO) is the most common cause of chronic renal failure in children. Rapid diagnosis is important to preserve function and/or to slow down renal injury. This study was to examine serum and urinary procollagen III aminoterminal propeptide (sPIIINP/uPIIINP) protein as potential biomarkers of obstruction in hydronephrosis.

METHODS

The study included 29 children with unilateral UPJO who underwent pyeloplasty (Group 1), 30 children with mild, nonobstructive hydronephrosis (Group 2), and 30 healthy children. In Group 1, serum and voided urine samples were obtained at preoperative, 3 days, and 3, 6 and 12 months after pyeloplasty, respectively. Meanwhile, additional urine from the affected pelvis was collected at surgery. Serum and voided urine were evaluated for PIIINP in each group using immunoenzymatic enzyme-linked immunosorbent assay (ELISA) commercial kits and were expressed in picograms per milligram creatine (cr.).

RESULTS

The preoperative sPIIINP and uPIIINP levels were significantly greater in Group 1 than in other 2 groups. Three months after pyeloplasty, sPIIINP and uPIIINP levels had decreased significantly in Group 1 together with significant improvement of split renal function. Receiver operator characteristic (ROC) analyses revealed a good diagnostic profile for uPIIINP/cr. in identifying children with abnormal split renal function (<40%) [area under the curve (AUC) 0.789].

CONCLUSIONS

Increasing uPIIINP levels are associated with worsening obstruction. Additional studies are required to confirm a potential application uPIIINP as a useful biomarker for the diagnosis and progression of congenital obstructive nephropathy.

Feasibility of measuring 3-dimensional renal parenchymal volume to predict postnatal renal function in near-term fetuses with congenital hydronephrosis: a preliminary study

OBJECTIVES

The purposes of this study were to evaluate the feasibility of predicting kidney function using the fetal renal parenchymal volume as determined by prenatal 3-dimensional (3D) sonography and to determine the association among the prenatal renal pelvic diameter, renal parenchymal volume, and postnatal renal function in near-term fetuses with unilateral hydronephrosis.

METHODS

This retrospective study included 42 kidneys (21 normal and 21 hydronephrotic) from 21 fetuses between 30 and 39 weeks' gestation. We used the extended imaging virtual organ computer-aided analysis (XI VOCAL; 10 planes) technique for the prenatal volumetric measurements, and postnatal renal function was estimated using renal scintigraphy. An independent-samples Student ttest, Spearman's rank correlation, and simple linear regression were used for the statistical analyses. Reproducibility was confirmed with a paired Student t test and intraclass correlation coefficients.

RESULTS

The renal pelvic diameter correlated well with the renal parenchymal volume Spearman ρ = 0.765; P < .001). The postnatal renal function correlated with the adjusted 3D renal parenchymal volume (Spearman ρ = -0.321; P = .043) but did not correlate with the prenatal renal pelvic diameter (Spearman ρ = -0.291; P = .062).

CONCLUSIONS

This preliminary study showed that 3D renal parenchymal volume could be a coparameter for predicting postnatal renal function with the renal pelvic diameter. Further studies in a larger population are required to obtain robust results.

Urinary proteome analysis at 5-year followup of patients with nonoperated ureteropelvic junction obstruction suggests ongoing kidney remodeling

PURPOSE

Severe ureteropelvic junction obstruction is treated surgically. However, for milder cases most clinical teams adopt a watchful waiting approach and only operate in the presence of significant decline of renal function combined with severe hydronephrosis. Little is known about the long-term consequences of ureteropelvic junction obstruction.

MATERIALS AND METHODS

Using capillary electrophoresis coupled with mass spectrometry, we analyzed the urinary proteome of 42 patients with ureteropelvic junction obstruction 5 years postoperatively or 5 years following spontaneous resolution.

RESULTS

At 5-year followup urinary proteomes were similar between patients with early surgical correction of ureteropelvic junction obstruction and age matched controls. In contrast, urinary proteomes differed significantly between conservatively followed patients and controls. Analyses of the proteomic differences suggested ongoing renal or ureteral remodeling in the conservatively followed patients that was not visible clinically.

CONCLUSIONS

Long-term followup studies are warranted in patients with ureteropelvic junction obstruction, especially those followed conservatively, to determine whether the observed changes in the urinary proteomes become clinically relevant at a later stage.

Congenital ureteropelvic junction obstruction: human disease and animal models

Ureteropelvic junction (UPJ) obstruction is the most frequently observed cause of obstructive nephropathy in children. Neonatal and foetal animal models have been developed that mimic closely what is observed in human disease. The purpose of this review is to discuss how obstructive nephropathy alters kidney histology and function and describe the molecular mechanisms involved in the progression of the lesions, including inflammation, proliferation/apoptosis, renin-angiotensin system activation and fibrosis, based on both human and animal data. Also we propose that during obstructive nephropathy, hydrodynamic modifications are early inducers of the tubular lesions, which are potentially at the origin of the pathology. Finally, an important observation in animal models is that relief of obstruction during kidney development has important effects on renal function later in adult life. A major short-coming is the absence of data on the impact of UPJ obstruction on long-term adult renal function to elucidate whether these animal data are also valid in humans.

Postoperative outcome following pyeloplasty in children using miniflank incision and transanastomotic stent: a prospective observational study

PURPOSE

To assess the postoperative outcome in children undergoing pyeloplasty, using a single transanastomotic indigenized stent.

METHODS

329 pyeloplasties were performed by small miniflank incision (3-5 cm) with lateral position for unilateral cases and prone position for bilateral cases during 1993-2009. The procedure involved decompression of the hydronephrotic sac, single layer anastomosis at the PUJ using 5/6-0 suture (reduction of the pelvis if required). An indigenized # 6, Teflon transanastomotic stent (TAS) with multiple holes (modified recently to a self-retaining loop in pelvis) was placed and taken out through the renal pelvis and the main skin incision. The stent served both as a nephrostomy and a stent. The kidney was not mobilized during the procedure. Postoperative results were assessed for early complications.

RESULTS

The mean age of the patients was 3.4 years (1 month-14 years). Bilateral simultaneous pyeloplasties were done in 16 cases with a mean age of 5.6 months (2-12). The stent was removed after 4-5 days in most cases after confirming distal flow on clamping. The post-operative complications included slippage of stent (11), blockage/nondrainage (7), difficult retrieval (4), urine leak (4), urinoma (3) and post-operative infection (1). DTPA scan at 3 months follow-up depicted improved drainage in 271 units, preserved renal function in 58 units and improved renal function more than 5% in 246 units.

CONCLUSION

Pyeloplasty using a single Teflon TAS is helpful not only in achieving effective drainage in children undergoing pyeloplasty, but also avoids the complications usually encountered with the use of nephrostomies, or double J stents.

Mechanisms of renal injury and progression of renal disease in congenital obstructive nephropathy

Congenital obstructive nephropathy accounts for the greatest fraction of chronic kidney disease in children. Genetic and nongenetic factors responsible for the lesions are largely unidentified, and attention has been focused on minimizing obstructive renal injury and optimizing long-term outcomes. The cellular and molecular events responsible for obstructive injury to the developing kidney have been elucidated from animal models. These have revealed nephron loss through cellular phenotypic transition and cell death, leading to the formation of atubular glomeruli and tubular atrophy. Altered renal expression of growth factors and cytokines, including angiotensin, transforming growth factor-beta, and adhesion molecules, modulate cell death by apoptosis or phenotypic transition of glomerular, tubular, and vascular cells. Mediators of cellular injury include hypoxia, ischemia, and reactive oxygen species, while fibroblasts undergo myofibroblast transformation with increased deposition of extracellular matrix. Progression of the lesions involves interstitial inflammation and interstitial fibrosis, both of which impair growth of the obstructed kidney and result in compensatory growth of the contralateral kidney. The long-term outcome depends on timing and severity of the obstruction and its relief, minimizing ongoing injury, and enhancing remodeling. Advances will depend on new biomarkers to evaluate the severity of obstruction, to determine therapy, and to follow the evolution of lesions.

Modified Differential Renal Function Measurement Revised by Renal Cross Sectional Area in Children with Ureteropelvic Junction Obstruction

Purpose

Diuretic ^99mTc-diethylenetriaminepentaacetic acid (Tc-DTPA) renal scans may show false-negative or false-positive results in children with ureteropelvic junction obstruction (UPJO). We evaluated whether modified differential renal function (DRF) revised by the renal cross-sectional area on imaging study may be a more valuable predictor than conventional DRF on a renal scan for deciding on a proper interventional time.

Materials and Methods

Between September 2001 and January 2008, we reviewed the diuretic renal scan results of 29 pediatric patients who underwent pyeloplasty due to unilateral UPJO. Diuretic renal scans using the standard ^99mTc-DTPA protocol and imaging studies for renal unit measurement area were done. Conventional DRF measurement and modified calculation of DRF per unit area were done. Conventional DRF was classified into group I (below 40%) and group II (above 40%).

Results

The mean age of all patients was 42.6±52.6 months (range, 3-198 months). The mean cross-sectional areas of the UPJO kidney and of the normal contralateral kidney were 62.1±29.2 cm² and 41.3±22.5 cm², respectively (p<0.01). The conventional and modified DRF of the UPJO kidney were 45.2±9.2% and 35.2±9.5%, respectively (p<0.01). Thirteen children (62%) in group II (n=21) were classified in group I by the modified DRF measurement.

Conclusions

The modified DRF measurement calculated according to cross-sectional area showed fewer false-negative results and may be a valuable method for deciding on pyeloplasty under equivocal circumstances.

Evaluation of UPJ obstruction before and after pyeloplasty using MR urography

This article builds on the previous article in this symposium and shows how MR urography contributes to the postoperative evaluation of children with UPJ obstruction. By analyzing the postoperative results, we derived new insights into their preoperative evaluation. With MR urography we combine simultaneous physiological and anatomic evaluation that enables us to identify changes in renal pathophysiology that occur in association with impaired drainage and obstruction. We studied 35 children before and after pyeloplasty. The pyeloplasty was considered successful in 30 and unsuccessful in 5. Both anatomic and functional criteria were used. The anatomic parameters included the degree of hydronephrosis, the appearance of the renal parenchyma, the quality of the nephrogram and the presence of crossing vessels. The functional criteria included the renal transit time, the calyceal transit time, the volumetric differential function, the Patlak differential function, the difference between the volumetric and Patlak differential function and the Patlak number per milliliter of renal tissue. No single parameter was sufficient to fully characterize UPJ obstruction, but by synthesizing all the information we were able to subdivide UPJ obstruction into compensated, decompensated and uropathic kidneys. Decompensated systems had the most significant improvement following successful pyeloplasty. Compensated systems showed little improvement in renal function, and uropathic kidneys were associated with a poor prognosis. It is clear that not all UPJ obstructions are the same, and it seems logical that treatment should be individually tailored rather than using a standard approach for all cases. Because MR urography can identify pathophysiological differences in children with UPJ obstruction that are occult to renal scintigraphy, it has an important potential role in identifying those who will benefit most from pyeloplasty and those who are probably best observed.

Chronic partial ureteral obstruction and the developing kidney

Although congenital urinary tract obstruction is a common disorder, its pathophysiology remains poorly understood and clinical practice is controversial. Animal models have been used to elucidate the mechanisms responsible for obstructive nephropathy, and the models reveal that renal growth and function are impaired in proportion to the severity and duration of obstruction. Ureteral obstruction in the neonatal rat or mouse leads to activation of the renin-angiotensin system, renal infiltration by macrophages, and tubular apoptosis. Nephrons are lost by glomerular sclerosis and the formation of atubular glomeruli, and progressive injury leads to tubular atrophy and interstitial fibrosis. Recovery following release of obstruction depends on the timing, severity, and duration of obstruction. Growth factors and cytokines are produced by the hydronephrotic kidney, including MCP-1 and TGF-beta1, which are excreted in urine and can serve as biomarkers of renal injury. Because MRI can be used to monitor renal morphology, blood flow, and filtration rate, its use might supplant current imaging modalities (ultrasonography and diuretic renography), which have significant drawbacks. Combined use of MRI and new urinary biomarkers should improve our understanding of human congenital obstructive nephropathy and should lead to new approaches to evaluation and management of this challenging group of patients.

Clinical and molecular markers of chronic interstitial nephropathy in congenital unilateral ureteropelvic junction obstruction

PURPOSE

We evaluated clinical and biological variables, and their meaning as reliable markers of chronic interstitial nephropathy in a selected group of children with prenatally detected hydronephrosis who underwent pyeloplasty because of congenital unilateral ureteropelvic junction obstruction.

MATERIALS AND METHODS

We reviewed the clinical, prenatal and postnatal ultrasonographic, and scintigraphic records of children for whom intraoperative biopsy records were available. We performed histological analysis, and evaluated tubulointerstitial immunostaining for vimentin and alpha-smooth muscle actin, and the immunohistochemical and mRNA expression of the renin-angiotensin system peptides and transforming growth factor-beta1.

RESULTS

The children were divided in 2 groups according to the absence (group 1) or presence (group 2) of chronic interstitial nephropathy in the biopsy. Patients in group 2 were significantly younger at prenatal diagnosis (p = 0.031), and had decreased split renal function (p = 0.005) and worse drainage (p = 0.035) on preoperative diuretic renography. No differences were found in terms of degree of hydronephrosis, or its prenatal and postnatal variation. Group 2 biopsies exhibited greater immunostaining for alpha-smooth muscle actin and vimentin (p = 0.004 and p = 0.047, respectively), and transforming growth factor-beta1 mRNA levels (p = 0.06). Vimentin and alpha-smooth muscle actin positivity correlated with renin, angiotensin II receptors 1 and 2, and transforming growth factor-beta1 mRNA levels, and all correlated with preoperative split renal function and post-void washout.

CONCLUSIONS

In congenital unilateral ureteropelvic junction obstruction chronic interstitial nephropathy and poor postoperative recovery seem to be associated with an earlier diagnosis of hydronephrosis, functional loss greater than 10% and worse scintigraphic drainage. Moreover, there is a strong correlation between molecular fibrogenic markers and histologically and scintigraphically demonstrated renal damage.

Renal biopsy in congenital ureteropelvic junction obstruction: evidence for parenchymal maldevelopment

The renal histologic changes associated with congenital ureteropelvic junction obstruction (UPJO) and the relationship to clinical imaging have not been well studied. In order to better understand the histologic alterations of congenital UPJO and their relationship with clinical imaging and outcomes, we examined renal biopsies from 61 patients undergoing pyeloplasty for congenital UPJO. Glomeruli were analyzed for various injury patterns and the tubulointerstitium was examined for tubular atrophy/simplification and fibrosis. Two methods were used to evaluate tubular mass: glomerular density and morphometric measurement of tubular size and density. Control specimens were obtained from age-matched autopsy specimens without renal pathology. Glomerular changes were identified in 73% of all biopsies and were present in a range from 1.7 to 91% of glomeruli in each patient. Overt tubulointerstitial changes were present in 26% of all biopsies. Fibrosis was noted to occur with tubulointerstitial changes in a significantly greater fraction of children over the age of 1 year (P=0.026). Increased glomerular density was associated with severe hydronephrosis (P<0.02). Normal glomerular density was inversely correlated with age (P<0.001), but this relationship was more variable in UPJO (P<0.01). Among patients with intact differential function preoperatively (>45%), postoperative functional decline was predicted only by increased glomerular density. 20 biopsies without overt tubulointerstitial changes were analyzed morphometrically and showed a significant reduction in proximal tubular (PT) size, but unchanged density. Distal tubular (DT) size was unchanged in UPJO, but density was increased. The PT/DT ratio was therefore markedly decreased in UPJO (P<0.0001). Both PT and DT sizes were significantly larger in children with a diuretic renogram washout time less than 20 min than those with greater than 20 min, a common threshold for functionally significant obstruction (P<0.05). Capsular thickness was significantly increased in UPJO. In all, 36% of biopsies had a thickness >0.5 mm and this was associated with greater degrees of tubulointerstitial changes and glomerular alterations. Congenital UPJO produces a variety of renal parenchymal changes, which may in part reflect abnormal development. Some of these alternations are seen in clinical imaging and may help predict outcomes, but there is significant discordance between conventional imaging and histological findings.

Postnatal unilateral pelviureteral junction obstruction: impact of pyeloplasty and conservative management on renal function

OBJECTIVES

To study the effect of pyeloplasty and conservative management on renal function in children with pelviureteral junction obstruction.

METHODS

This prospective study included 65 children postnatally diagnosed with unilateral pelviureteral junction obstruction. On the basis of the patients' symptoms and technetium-99m diethylenetriamine pentaacetic acid renal isotope scan findings, symptomatic patients or those with split function of the corresponding kidney of 40% or less were assigned to group 1 (n = 35) and underwent pyeloplasty. Asymptomatic patients with split function greater than 40% (group 2, n = 30) were treated conservatively. Patients who showed deterioration of renal function underwent pyeloplasty. The effect of both lines of treatment on renal function was evaluated.

RESULTS

After pyeloplasty, group 1 had improvement in the glomerular filtration rate (GFR) in 30 (85.7%), stabilization in 2 (5.7%), and deterioration in 3 (8.6%) patients. In group 1, the comparison between the mean value of the baseline GFR (17.1 +/- 7.7 mL/min) and its mean value at follow-up (28 +/- 6.3 mL/min) showed an increase of statistical significance (P <0.01). In the group 2 patients, conservative treatment resulted in improvement in the GFR in 12 (40%), stabilization in 3 (10%), and deterioration in 15 (50%) patients. In group 2, no significant difference was found between the mean baseline GFR (29.8 +/- 9.8 mL/min) and its mean value at follow-up (31.2 +/- 5.6 mL/min).

CONCLUSIONS

In patients with postnatal pelviureteral junction obstruction, early pyeloplasty is recommended if the corresponding GFR is 40% or less. Conservative management in patients with better function resulted in deterioration of renal function in 50%. Should this policy of treatment be chosen, meticulous follow-up is mandatory.

Variable chronic partial ureteral obstruction in the neonatal rat: a new model of ureteropelvic junction obstruction

BACKGROUND

Congenital ureteropelvic junction (UPJ) obstruction is a common developmental anomaly. To elucidate the mechanisms underlying the renal consequences of congenital UPJ obstruction, we have developed a new model of variable partial unilateral ureteral obstruction (UUO) in the neonatal rat.

METHODS

Rat pups were subjected to sham-operation, complete UUO, or variable partial UUO within the first day of life. After 14 or 28 days, the relative number of glomeruli, cell proliferation, tubular apoptosis, tubular atrophy, and interstitial fibrosis were quantitated in histologic sections. Glomerular filtration rate (GFR) was determined after 28 days of partial or complete UUO.

RESULTS

Following 70% to 75% reduction in ureteral diameter, renal growth from 14 to 28 days was reduced by 60%, and the number of glomeruli decreased by 50%. Renal pelvic diameter increased in proportion to the severity of obstruction following 14 days of partial UUO, and by 28 days, was maximally dilated regardless of the luminal diameter. Renal proliferation was increased, while tubular apoptosis, tubular atrophy, and interstitial fibrosis were less severe 14 days following partial UUO than in complete UUO. GFR was reduced by 80%, and proteinuria developed following 28 days of partial UUO.

CONCLUSION

Renal function is impaired by chronic ipsilateral partial UUO, which reduces the number of nephrons, and leads to progressive renal pelvic dilatation. Tubular atrophy and interstitial fibrosis develop prior to significant renal pelvic dilatation. Correlation of clinically measurable parameters with renal morphometry or imaging studies in this model may lead to new approaches to the management of congenital UPJ obstruction.

ELASTIN CONTENT OF THE RENAL PELVIS AND URETER DETERMINES POST-PYELOPLASTY RECOVERY

PURPOSE

We evaluated the collagen-to-smooth muscle tissue matrix ratio and percentage of elastin in the renal pelvis, ureteropelvic junction (UPJ) and ureter, and compared these findings with the degree of obstruction, patient age and post-pyeloplasty renal recovery.

MATERIALS AND METHODS

We analyzed histological sections from 75 patients with UPJ obstruction. Nine patients were excluded owing to bilateral UPJ obstruction and an improper specimen. We divided the specimen obtained from pyeloplasty into 3 parts, namely the renal pelvis above the obstruction, the obstructed UPJ portion and the ureter below the obstruction. To examine the collagen and smooth muscle, sections were stained using Masson's trichrome, and elastic van Giesson stain was used for elastin, smooth muscle and collagen. Collagen, smooth muscle and elastin populations were identified, and the tissue matrix ratio and percentage of elastin were calculated by color image analysis.

RESULTS

In patients with lower ratios of collagen-to-smooth muscle in the UPJ proper hydronephrosis was more improved postoperatively (p = 0.049). In patients with a lower percentage of elastin in the renal pelvis, UPJ and ureter hydronephrosis was more improved postoperatively (p <0.0001).

CONCLUSIONS

Because the UPJ portion was resected during pyeloplasty, the renal pelvis and the ureter remaining after pyeloplasty are likely to be related to improved hydronephrosis. A higher percentage of elastin in the renal pelvis and ureter contributes to inelasticity and low compliance, and results in a slower recovery from hydronephrosis after pyeloplasty.

[The uteropelvic junction in children: from the clinical problems to the morphogenetic approach]

The responsibility of the uteropelvic junction (UPJ) syndrome or abnormalities for renal affections and also for high obstructive uropathy is well-known. But, controversies still remain about the anatomic approach of this clinical feature. Our purpose is to elucidate the developmental anatomy of UPJ and eventually to set the steps of the anatomic approach of the UPJ abnormalities. This study also leads to a better understanding of the mechanism of the intrinsic ureteropelvic junction obstructions. A total number of 122 post-mortem specimens with ages ranging from 1 day to 30 months in both sexes underwent formalin treatment for histological investigation. We performed both transverse and longitudinal sections. Hematein-eosin-safran and Masson's trichrome staining were used. Histological examination revealed that myoarchitecture of UPJ set increasingly up. Circular muscle fibers were first to put in. They had an initial arrangement as a ring in neonates and infants. We conclude that circular layer appears first and sooner than others. On the other hand, coincidence in time between ages of our specimens and ages of patients sufferning from UPJ syndrome leads to further investigations to determine the implication of ring-shaped circular layer in intrinsic 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.

Unilateral ureteropelvic junction obstruction in children: long-term followup after unilateral pyeloplasty

PURPOSE

The benefit of surgery on renal function in unilateral ureteropelvic junction stenosis (UPJS) is still debated. We evaluated renal function outcome after unilateral pyeloplasty in 53 children.

MATERIALS AND METHODS

We retrospectively reviewed 123I-hippuran renography performed at diagnosis and 5 to 15 years (mean +/- SD 7 +/- 3 years) after successful pyeloplasty. UPJS was prenatally detected in 26 children because of urinary tract infection in 17 and miscellaneous reasons in 10. Relative function (RF) and absolute function were measured on background corrected renograms. Absolute function of the affected and contralateral kidneys was determined by an accumulation index (AI), representing the percent injected dose extracted by each kidney 30 to 90 seconds after the heart peak.

RESULTS

Preoperatively 33 of the 53 UPJS kidneys had a decreased AI but only 8 had a RF of less than 40%, which was improved in 7 at followup. In addition, the AI improved in 29 kidneys, of which 19 (36%) normalized. Of the UPJS kidneys 14 had an initially decreased AI that remained abnormal at followup. In these kidneys preoperative RF was less than 40% in all. At followup RF was greater than 40% in 4 children, in whom the AI of the UPJS kidney did not improve but the AI of the contralateral one decreased from supranormal to normal. Seven contralateral kidneys had a supranormal AI, whereas the AI remained normal in 3, of which the RF in the UPJS kidney remained at less than 40%. The AI and RF were normal in 20 UPJS kidneys and remained normal.

CONCLUSIONS

When normal, the AI and RF reflected renal function outcome similarly. The AI added relevant information in UPJS kidneys with impaired function, showing compensation of the contralateral kidney.

Antenatally detected, unilateral dilatation of the renal pelvis: a critical review. 2. postnatal non-operative treatment--long-term hazards, urgent research

BACKGROUND

Even after two decades, there is still much discussion about the postnatal treatment of antenatally detected, isolated pelvic dilatation (consistent with pyelo-ureteral junction obstruction). A recent review concluded that non-operative expectancy seemed safe - even after 17 years in certain cases. However, the final outcome, i.e. when these children have reached old age, is remote.

OBJECTIVE

This review takes stock of conceivable long-term hazards and evaluates prognosticating tools, and offers a basis for protocols for future randomized controlled trials. Long-term hazards: Symptoms in this context are generally considered ominous. In the antenatally detected cases, i.e. primarily asymptomatic, symptoms have been reported but they were not necessarily combined with renal damage. Hydronephroses, so mild, that they are written off, may deteriorate later on (indeed insidiously), although probably seldom. Urgent research: A predictor of outcome is eagerly pursued but hard to obtain, due to the difficulty in defining true obstruction in compliant systems such as the urinary one. Ordinary diagnostics offer no help, but there are promising innovations: constant pressure/flow assessment (flow necessary to keep a preset intrapelvic pressure), NAG/creatinine in pelvic urine, and TGFbeta-1 in voided urine. Renal microstructure, sometimes severely damaged early (which disagrees with the good results with expectancies) could possibly herald future deterioration.

CONCLUSION

Adverse developments should be meticulously documented and published swiftly, so policy can be changed if necessary, before it is too late. Cognizance of their existence, not necessarily frequency and statistics, is then first order. Efforts to design prognosticating tools has also high priority.

Unilateral ureteral obstruction in neonatal rats leads to renal insufficiency in adulthood

BACKGROUND

Although unilateral ureteropelvic junction obstruction is the most common cause of congenital obstructive nephropathy in infants and children, management remains controversial, and follow-up after pyeloplasty is generally limited to the pediatric ages. We have developed a model of temporary unilateral ureteral obstruction (UUO) in the neonatal rat: One month following the relief of five-day UUO, the glomerular filtration rate (GFR) of the postobstructed kidney was normal despite a 40% reduction in the number of glomeruli and residual vascular, glomerular, tubular, and interstitial injury.

METHODS

To determine whether hyperfiltration and residual injury of remaining nephrons leads to progression of renal insufficiency in later life, 31 rats were sham operated or subjected to left UUO at one day of age, with relief of UUO five days later, and were studied at one year of age. GFR was measured by inulin clearance, and the number of glomeruli, tubular atrophy, glomerular sclerosis, and interstitial fibrosis were measured by histomorphometry in sham, obstructed (UUO), and intact opposite kidneys. Intrarenal macrophages and alpha-smooth muscle actin were identified by immunohistochemistry.

RESULTS

Despite relief of UUO, ultimate growth of the postobstructed kidney was impaired. The number of glomeruli was reduced by 40%, and GFR was decreased by 80%. However, despite significant compensatory growth of the opposite kidney, there was no compensatory increase in GFR, and proteinuria was increased. Moreover, glomerular sclerosis, tubular atrophy, macrophage infiltration, and interstitial fibrosis were significantly increased not only in the postobstructed kidney, but also in the opposite kidney.

CONCLUSIONS

Although GFR is initially maintained following relief of five-day UUO in the neonatal rat, there is eventual profound loss of function of the postobstructed and opposite kidneys because of progressive tubulointerstitial and glomerular damage. These findings suggest that despite normal postoperative GFR in infancy, children undergoing pyeloplasty for ureteropelvic junction obstruction should be followed into adulthood. Elucidation of the cellular response to temporary UUO may lead to improved methods to assess renal growth, injury, and functional reserve in patients with congenital obstructive nephropathy.