Urinary tract obstruction in children

Decreased percent change in renal pelvis diameter on diuretic functional magnetic resonance urography following administration of furosemide may help characterize unilateral uretero-pelvic junction obstruction

BACKGROUND

A well-established definition of obstruction in the setting of congenital hydronephrosis is lacking. Multiple imaging modalities and radiographic characteristics or parameters have been described to help confirm the diagnosis of ureteropelvic junction obstruction (UPJO). We sought to evaluate the change in anterior-posterior renal pelvic diameter (APRPD) following furosemide administration in patients with unilateral hydronephrosis and confirmed UPJO on functional magnetic resonance urography (fMRU) who underwent pyeloplasty.

MATERIALS AND METHODS

There were 49 patients who met inclusion criteria (11 females, 38 males; average age 2.2 years, SD 3.4 years) from February 2006 to September 2020, diagnosed with unilateral hydronephrosis (SFU Grade 3-4) who underwent fMRU prior to pyeloplasty for confirmed UPJO. 29 of the included patients also underwent a post-pyeloplasty fMRU. A weight-adjusted dose of 1 mg/kg of furosemide (max 20 mg/kg) was administered intravenously. Two board-certified pediatric radiologists measured the APRPD of the obstructed and non-dilated kidneys prior to pyeloplasty and APRPD of the hydronephrotic kidneys on the post-pyeloplasty follow up fMRUs. Measurements were performed on images prior to and approximately 30 min following furosemide injection.

RESULTS

The average APRPD before furosemide injection in the obstructed kidney prior to pyeloplasty was 26.3 mm (SD 9.0 mm) compared to the non-dilated (not obstructed) kidney measurement of 5.1 mm (SD 3.6 mm) (p < 0.001). Following administration of furosemide, the average APRPD was 31.4 mm (SD 8.8 mm) in the obstructed kidney, and 7.8 mm (SD 4.1 mm) in the non-dilated kidney (p < 0.001). After pyeloplasty, the pre-furosemide APRPD measurement was 17.8 mm (SD 11 mm), which was significantly less compared to the pre-pyeloplasty APRPD (p < 0.001). The post-pyeloplasty, post-furosemide APRPD measurement was 25.8 mm (SD 12 mm), also significantly less compared to the pre-pyeloplasty measurement (p = 0.02). The changes in APRPD in the obstructed kidney prior to pyeloplasty was 5.1 mm (SD 3.5 mm) and after pyeloplasty was 8 mm (SD 4.6 mm) (p = 0.002). Change in APRPD in the non-dilated kidney was 2.7 mm (SD 2.3 mm). Percent APRPD change in the obstructed kidney was 22.9% (SD 18.5%), which was significantly less than 33.3% (SD 22.1%) in the post-pyeloplasty kidney (p = 0.028) and 82.8% (SD 87.9%) in the non-dilated kidney (p < 0.001).

CONCLUSIONS

A relatively smaller change in APRPD on fMRU following administration of furosemide in the setting of UPJO may serve as another predictive characteristic of obstructed kidneys.

CAKUT: A Pediatric and Evolutionary Perspective on the Leading Cause of CKD in Childhood

The global prevalence of chronic kidney disease (CKD) is increasing rapidly, due to increasing environmental stressors through the life cycle. Congenital anomalies of kidney and urinary tract (CAKUT) account for most CKD in children, with a spectrum that can lead to kidney failure from early postnatal to late adult life. A stressed fetal environment can impair nephrogenesis, now recognized as a significant risk factor for the development of adult CKD. Congenital urinary tract obstruction is the leading cause of CKD due to CAKUT and can itself impair nephrogenesis as well as contribute to progressive nephron injury. Early diagnosis by ultrasonography in fetal life by an obstetrician/perinatologist can provide important information for guiding prognosis and future management. This review focuses on the critical role played by the pediatrician in providing timely evaluation and management of the patient from the moment of birth to the transfer to adult care. In addition to genetic factors, vulnerability of the kidney to CKD is a consequence of evolved modulation of nephron number in response to maternal signaling as well as to susceptibility of the nephron to hypoxic and oxidative injury. Future advances in the management of CAKUT will depend on improved biomarkers and imaging techniques.

Functional recoverability post-pyeloplasty in children with ureteropelvic junction obstruction and poorly functioning kidneys: Systematic review

BACKGROUND

The management of poorly functioning kidneys (PFK) associated with ureteropelvic junction obstruction (UPJO) is controversial. There is contradictory information about how to best manage these cases: pyeloplasty or nephrectomy?

OBJECTIVE

To systematically summarize the available evidence concerning the effects of pyeloplasty on the differential renal function of PFK in children with unilateral UPJO, highlighting the ongoing challenges in their definition, management, and long-term follow-up. In addition, we aim to verify potential predictors of renal functional recoverability that could help clinicians choose candidates for pyeloplasty.

METHODS

We searched several databases including PubMed, Embase, and Cochrane Library CENTRAL until August 20, 2021, according to the PRISMA guidelines. The following concepts were searched: pediatric, ureteropelvic junction obstruction, UPJO, pyeloplasty, recovery, split renal function, and differential renal function. We enrolled studies where the PFK was defined as preoperative differential renal function (DRF) ≤30% by renal scintigraphy. Potential predictors of renal functional recoverability were assessed and compared among studies. The quality of the included studies was evaluated using a modified version of the Newcastle-Ottawa scale (NOS).

RESULTS

1499 citations perceived as relevant to screening were retrieved. After screening, 20 studies were included, comprising a total of 625 cases. The number of patients in each study varied between 5 and 84, while the average post-surgical follow-up duration ranged between 3 months and 180 months. The most significant preoperative predictive factor for postoperative functional recoverability was the baseline DRF, especially when antenatally diagnosed. The quality was considered average in a significant portion of included studies.

CONCLUSION

A significant proportion of PFK showed an increase of DRF post-pyeloplasty. However, no consistent predictive factors for functional recoverability have yet been determined apart from preoperative DRF. Until further evidence appears, pyeloplasty should be considered a valid option in the armamentarium of UPJO management in PFK.

Validation of modified diuretic drainage times criteria in congenital hydronephrosis

INTRODUCTION AND OBJECTIVE

The value of diuretic renography drainage times in congenital hydronephrosis (AHN) decision making is controversial. Recently, a group suggested a modification to the classically described diuretic drainage time cut-off values. They found that a drainage half-time (T_1/2) < 5 min was normal whereas a T_1/2 exceeding 75 min predicted pyeloplasty. In addition, they reported on the benefit of a delayed drainage image obtained with gravity assistance. We sought to evaluate the ability of these modified T1/2 criteria to predict pyeloplasty, alone or in combination with a delayed drainage image referred to as Global Washout (GWO).

METHODS

We retrospectively reviewed 113 patients, including consecutive pyeloplasties for AHN from 2004 to 2018. Patients who underwent pyeloplasty due to low differential renal function (DRF) < 30% or infection were excluded. The control group comprised high grade AHN managed non-operatively. The initial renal ultrasound and MAG 3 Lasix renogram were reviewed for grade, differential renal function (DRF), T_1/2 and GWO. A ROC curve was used to evaluate the T_1/2 and GWO cut-off points that can predict pyeloplasty, using a p-value of less than 0.05.

RESULTS

The pyeloplasty group consisted of 62 patients and the control group consisted of 51 patients. Two patients (3%) in the pyeloplasty group had a T_1/2 < 5 min whereas 21 (34%) had T _1/2 > 75 min (p < 0.001). In the control group, 25 patients (49%) had T _1/2 < 5 min and none had T_1/2 >75 min (P < 0.001). The ROC curve for T_1/2 < 5 min demonstrated 94% sensitivity and 51% specificity whereas a T_1/2 >75 min demonstrated 100% specificity and 34% sensitivity. Analysis of the GWO using a ROC curve revealed that a cut-off of 50% GWO has 100% specificity and 52% sensitivity for pyeloplasty. Overall, a T1/2 > 75 min or GWO <50% predicted 53% of pyeloplasties (Fig A) and was absent in all conservatively managed cases.

DISCUSSION

The limitations of the present study include its retrospective nature. Secondly, the lack of a gold standard diagnostic test for uretero-pelvic junction obstruction hampers objective quantification of diagnostic test utility performance.

CONCLUSIONS

We confirm the utility of the modified diuretic half-time criteria and delayed gravity assisted imaging. A T1/2 > 75 min or GWO <50% are indicators of severity whereas a T1/2 of <5 min or GWO >90% is reassuring. Gravity assisted delayed imaging can be especially helpful in cases with indeterminate T 1/2 times and should be included in the standard assessment of hydronephrotic kidneys. These parameters can be used to tailor the frequency and invasiveness of imaging within observation protocols.

Urinary extracellular matrix proteins as predictors of the severity of ureteropelvic junction obstruction in children

INTRODUCTION

Ureteropelvic junction obstruction (UPJO) particularly represents a challenge in regard to management, as not all hydronephrosis (HN) represent a kidney-damaging state. Urinary biomarkers have been proposed as noninvasive tools. Extracellular matrix (ECM) proteins are associated with tissue fibrosis in the setting of UPJO and is poorly explored.

OBJECTIVE

To investigate whether urinary ECM proteins are useful to discriminate the severity of urinary obstruction on unilateral UPJO.

STUDY DESIGN

Children with unilateral UPJO were prospective enrolled. Urinary (u) matrix metalloproteinases (MMP-1,-2,-9 and TIMP-1,-2) as well as clinical characteristics were measured in the following groups: 26 children with obstructive HN at initial diagnosis and after six months of dismembered pyeloplasty; 22 children with non-obstructive HN at diagnosis and after six months of observation; 26 children without any urinary tract condition, as the control group. Results were assessed statistically using for homogenous groups, a one-way analysis of variances (ANOVA) and for nonparametric groups, Mann-Whitney test or Kruskal-Wallis test was performed. ROC curves were performed.

RESULTS

Baseline samples demonstrated a higher concentration of uMMP-1/Cr, uMMP-2/Cr, u-TIMP-1/Cr and u-TIMP-2/Cr in obstructive HN group; uMMP-9/Cr levels were higher in non-obstructive HN group and all studied biomarkers had lower concentrations for the control group. On follow-up, for the obstructive HN group, urinary concentration of uTIMP-1/Cr and uTIMP-2/Cr decreased, and uMMP-1/Cr, uMMP-2/Cr and uMMP-9/Cr increased when comparing preoperative to postoperative values. In the non-obstructive HN group, all proteins analyzed were stable after six months of observation. ROC curves analysis showed a promising diagnostic profile for the detection of obstructive HN for uTIMP-1/Cr (area under the curve -AUC-; of 0.692), uTIMP-2/Cr (AUC of 0.678) and for uMMP-2/Cr (AUC of 0.655).

DISCUSSION

The severity of kidney obstruction could correlate with the urinary ECM proteins concentration in this study. This is concordant with prior studies demonstrating that a disruption of the balance of accumulation/degradation of the ECM proteins occur on obstructive uropathy. Limitations of our study include the older age of our patients and that these markers had no influence at all on the surgical decision.

CONCLUSION

We demonstrate that obstructive HN have significantly higher uMMP-2, uTIMP-1 and uTIMP-2 concentrations. Particularly, uTIMP-2 levels were correlated to severity of obstruction and therefore, it might be a useful urinary biomarker to correctly allocate children with HN between surgical management vs follow-up. After pyeloplasty, uTIMP-1 and uTIMP-2 presented a progressive decrease postoperatively, which is also highly desirable for urinary markers.

Can serum Neutrophil Gelatinase Associated Lipocalin and Kidney Injury Molecule-1 help in decision making for surgery in antenatally dedected hydronephrosis

INTRODUCTION

Congenital obstructive uropathies are among leading reasons for renal failure in children. Answers to questions such as what the critical threshold of obstruction is or which degree of obstruction disrupts the development of the kidney still remain unclear. Several biomarkers such as Kidney Injury Molecule 1 (KIM-1) and Neutrophil Gelatinase Associated Lipocalin (NGAL) may help clinicians in the clinical evaluation and appropriate planning of the disease.

OBJECTIVE

This study aimed to investigate whether serum and urinary KIM-1 and NGAL levels contribute to conventional methods in decision-making for surgery in the postnatal period of infants with antenatal hydronephrosis.

STUDY DESIGN

34 patients with the diagnosis of antenatal hydronephrosis were evaluated prospectively. Renal pelvis diameters of all patients were above 10 mm in the ultrasonography (USG). Patients underwent diuretic renal scintigraphy after neonatal period. Patients were divided into two groups as surgery or follow-up based on USG and scintigraphy findings. Blood and urine samples were collected at first visits in both groups and again at the 3. Postoperative month in the surgery group. Serum and urinary NGAL and KIM-1 levels were measured by ELISA method. Study data were compared through the Mann-Whitney U and Wilcoxon Signed-Ranks test.

RESULTS

There were 10 patients in the surgery group and 24 patients in the follow-up group. The age and gender did not differ between the groups. The surgery group had significantly higher median serum NGAL values (259.2 ng/mL) than that in the follow-up group (46.8 ng/mL, p = 0.028). The postoperative reduction of the median serum NGAL to 68.1 ng/mL compared to preoperative level was also found to be significant (p = 0.037) in the surgery group. Between the groups and within the surgery group no statistically significant difference was detected in terms of median urinary NGAL, and serum and urine KIM-1 levels.

DISCUSSION

USG and renal scintigraphy are frequently used in determining whether patients with antenatal hydronephrosis need surgical intervention in the postnatal period. Several new biomarkers might help clinicians in decision making for surgery. KIM-1 and NGAL levels can be measured both in urine and serum. To our knowledge, this is the only study where serum NGAL and KIM-1 levels were measured in patients with antenatal diagnosis. Small sample size, lack of long term findings and control group are limitations of our study.

CONCLUSION

Serum NGAL levels of patients with antenatal hydronephrosis may help in decision making on the surgical intervention.

State-of-the-Art Renal Imaging in Children

Imaging modalities for diagnosing kidney and urinary tract disorders in children have developed rapidly over the last decade largely because of advancement of modern technology. General pediatricians and neonatologists are often the front line in detecting renal anomalies. There is a lack of knowledge of the applicability, indications, and nephrotoxic risks of novel renal imaging modalities. Here we describe the clinical impact of congenital anomalies of the kidneys and urinary tract and describe pediatric-specific renal imaging techniques by providing a practical guideline for the diagnosis of kidney and urinary tract disorders.

Managing Ureteropelvic Junction Obstruction in the Young Infant

In the last decade, management of congenital UPJ obstruction has become progressively observational despite the lack of precise predictors of outcome. While it is clear that many children will have resolution of their hydronephrosis and healthy kidneys, it is equally clear that there are those in whom renal functional development is at risk. Surgical intervention for the young infant, under 6 months, has become relatively infrequent, yet can be necessary and poses unique challenges. This review will address the clinical evaluation of UPJO in the very young infant and approaches to determining in whom surgical intervention may be preferable, as well as surgical considerations for the small infant. There are some clinical scenarios where the need for intervention is readily apparent, such as the solitary kidney or in child with infection. In others, a careful evaluation and discussion with the family must be undertaken to identify the most appropriate course of care. Further, while minimally invasive pyeloplasty has become commonly performed, it is often withheld from those under 6 months. This review will discuss the key elements of that practice and offer a perspective of where minimally invasive pyeloplasty is of value in the small infant. The modern pediatric urologist must be aware of the various possible clinical situations that may be present with UPJO and feel comfortable in their decision-making and surgical care. Simply delaying an intervention until a child is bigger may not always be the best approach.

Ultrasound-Based Scoring System for Indication of Pyeloplasty in Patients With UPJO-Like Hydronephrosis

Background: Previous scoring systems have used renal scan parameters to assess severity of ureteropelvic junction obstruction-like hydronephrosis (UPJO-like HN), however this information is not always reliable due to protocol variation across centers and renogram limitations. Therefore, we sought to evaluate the Pyeloplasty Prediction Score (PPS), which utilizes only baseline ultrasound measurements to predict the likelihood of pyeloplasty in infants with UPJO-like. Methods: PPS was developed using three ultrasound parameters, Society of Fetal Urology (SFU) grade, transverse anteroposterior (APD), and the absolute percentage difference of ipsilateral and contralateral renal lengths at baseline. PPS was evaluated using prospectively collected prenatal hydronephrosis data (n = 928) of patients with UPJO-HN. Children with vesicoureteral reflux. primary megaureter, other associated anomalies, bilateral HN and <3 months of follow-up were excluded. Scores were analyzed regarding its usefulness in predicting which patients would be more likely to undergo pyeloplasty. Sensitivity, specificity, likelihood ratios (LR) and receiver operating characteristic (ROC) curve were determined. Results: Of 353 patients, 275 (78%) were male, 268 (76%) had left UPJO-like HN, and 81 (23%) had a pyeloplasty. The median age at baseline was 3 months (IQR 1-5). The PPS system was highly accurate in distinguishing patients who underwent pyeloplasty using baseline ultrasound measurements (AUC: 0.902). PPS of 7 and 8 were found to have a sensitivity of 85 and 78%, and specificity of 81 and 90%, respectively. PPS of 8 was associated with a LR of 7.8, indicating that these patients were eight times more likely to undergo pyeloplasty. Conclusion: Overall, PPS could detect patients more likely to undergo pyeloplasty using baseline ultrasound measurements. Those with a PPS of eight or higher were eight times more likely to undergo pyeloplasty.

First-year profile of biomarkers for early detection of renal injury in infants with congenital urinary tract obstruction

BACKGROUND

Diagnosis of renal function impairment and deterioration in congenital urinary tract obstruction (UTO) continues to be extremely challenging. Use of renal biomarkers in this setting may favor early renal injury detection, allowing for a reliable choice of optimal therapeutic options and prevention or minimization of definitive renal damage.

METHODS

This longitudinal, prospective study analyzed the first-year profile of two serum renal biomarkers: creatinine (sCr) and cystatin C (sCyC); and six urinary renal biomarkers: neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), transforming growth factor beta-1 (TGF-β1), retinol-binding protein (RBP), cystatin C (uCyC), and microalbuminuria (μALB) in a cohort of 37 infants with UTO divided into three subgroups: 14/37 with unilateral hydro(uretero)nephrosis, 13/37 with bilateral hydro(uretero)nephrosis, and 10/37 patients with lower urinary tract obstruction (LUTO), compared with 24 healthy infants matched by gestational age and birth weight.

RESULTS

All urine biomarkers showed significantly higher values at the first month of life (p ≤ 0.009), while NGAL (p = 0.005), TGF-ß1 (p < 0.001), and μALB (p < 0.001) were high since birth compared to controls. Best single biomarker performances were RBP in bilateral hydronephrosis and LUTO subgroups and KIM-1 in unilateral hydronephrosis subgroup. Best biomarker combination results for all subgroups were obtained by matching RBP with TGF-ß1 or KIM-1 and NGAL with CyC ([AUC] ≤ 0.934; sensitivity ≤ 92.4%; specificity ≤ 92.8%).

CONCLUSIONS

RBP, NGAL, KIM-1, TGF-ß1, and CyC, alone and especially in combination, are relatively efficient in identifying surgically amenable congenital UTO and could be of practical use in indicating on-time surgery.

The role of renal biomarkers to predict the need of surgery in congenital urinary tract obstruction in infants

INTRODUCTION

The diagnosis of renal function impairment and deterioration in congenital urinary tract obstruction (UTO) continues to be extremely challenging. The use of new renal biomarkers in this setting may favor early renal injury detection, allowing for a reliable choice of optimal therapeutic options and the prevention or minimization of definitive renal damage.

OBJECTIVE

The aim of the study was to investigate a selection of promising biomarkers of renal injury with the intention of evaluating and comparing their profile with clinically based decisions for surgical intervention of infants with congenital obstructive uropathies.

STUDY DESIGN

The first-year profile of renal biomarkers, serum creatinine (sCr), serum and urine cystatin C (CyC), neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), transforming growth factor beta-1 (TGF-β1), retinol-binding protein (RBP), and microalbuminuria (μALB), was analyzed in a cohort of 37 infants with congenital UTO, divided into three subgroups, 14 cases with grade III unilateral hydro(uretero)nephrosis, 13 cases with grade III bilateral hydro(uretero)nephrosis, and 10 cases with low urinary tract obstruction (LUTO), compared with 24 healthy infants matched by gestational age and birth weight. Serum and urine samples were stored at -70 °C and thereafter analyzed by quantitative enzymatic immunoassay.

RESULTS

Compared with the control group (Figure), all renal biomarker values were significantly increased in patients (P ≤ 0.02). In the unilateral hydronephrosis and LUTO group, RBP (P ≤ 0.043), NGAL (P ≤ 0.043), KIM-1 (P ≤ 0.03), and TGF-β1 (P ≤ 0.034) values dropped significantly after surgery. Neutrophil gelatinase-associated lipocalin alone and in combination with urine and serum CyC demonstrated the best performance in determining the need for surgery (area under the curve, 0.801 and 0.881, respectively). Biomarker profile analysis was suggestive of surgical intervention in 55.4% (7/13) of non-operated cases, and most of the biomarker values were above the cutoff levels within at least 3 months before the clinically based surgical decision in 58% (14/24) of all operated patients.

DISCUSSION

To the best of the authors' knowledge, this is the first study to present the clinical use of selected group of serum and urinary biomarkers in the setting of UTO to distinguish between patients who would benefit from surgery intervention. The most promising results were obtained using NGAL, RBP, TGF-β1, and KIM-1, especially in the unilateral hydro(uretero)nephrosis and LUTO subgroups when compared with the control group.

CONCLUSIONS

Urine biomarkers, alone and in combination, demonstrated high potential as a non-invasive diagnostic tool for identifying infants who may benefit from earlier surgical intervention.

Changes in cell fate determine the regenerative and functional capacity of the developing kidney before and after release of obstruction

Congenital obstructive nephropathy is a major cause of chronic kidney disease (CKD) in children. The contribution of changes in the identity of renal cells to the pathology of obstructive nephropathy is poorly understood. Using a partial unilateral ureteral obstruction (pUUO) model in genetically modified neonatal mice, we traced the fate of cells derived from the renal stroma, cap mesenchyme, ureteric bud (UB) epithelium, and podocytes using Foxd1Cre, Six2Cre, HoxB7Cre, and Podocyte.Cre mice respectively, crossed with double fluorescent reporter (membrane-targetted tandem dimer Tomato (mT)/membrane-targetted GFP (mG)) mice. Persistent obstruction leads to a significant loss of tubular epithelium, rarefaction of the renal vasculature, and decreased renal blood flow (RBF). In addition, Forkhead Box D1 (Foxd1)-derived pericytes significantly expanded in the interstitial space, acquiring a myofibroblast phenotype. Degeneration of Sine Oculis Homeobox Homolog 2 (Six2) and HoxB7-derived cells resulted in significant loss of glomeruli, nephron tubules, and collecting ducts. Surgical release of obstruction resulted in striking regeneration of tubules, arterioles, interstitium accompanied by an increase in blood flow to the level of sham animals. Contralateral kidneys with remarkable compensatory response to kidney injury showed an increase in density of arteriolar branches. Deciphering the mechanisms involved in kidney repair and regeneration post relief of obstruction has potential therapeutic implications for infants and children and the growing number of adults suffering from CKD.

A long-term follow-up in conservative management of unilateral ureteropelvic junction obstruction with poor drainage and good renal function

The aim of the study was to retrospectively review the outcome of neonatal ureteropelvic junction obstruction with a good renal function and a poor drainage at a first diuretic renal scan, in cases where surgery was recommended on the basis of a loss of renal function, worsening of hydronephrosis or occurrence of clinical symptoms. Hydronephrosis was graded from 1 to 4 or as ureteral tract dilatation (UTD) P1 to UTD P3. During follow-up, 15 out of 38 patients (34.2%) required surgery while 25 out of 38 (65.8%) could have been managed conservatively. In patients with grade 2, 3, and 4 hydronephrosis, the ureteropelvic junction obstruction resolved or improved spontaneously in 100%, 63%, and 33% of cases (in 100% of UTD P1, 67% of UTD P2, and 50% of UTD P3), respectively. The median of follow-up was 14 years. Chi-square test showed a significant relationship between initial grade of hydronephrosis or UTD and the possibility of an efficient conservative management (p = 0.0088 and p = 0.0460).Conclusion: Conservative management can be safely achieved in ureteropelvic junction obstruction with poor drainage. Scheduled controls are needed for early discovery of functional renal deterioration. High-grade hydronephrosis is unlikely to resolve spontaneously and is often accompanied by a loss of renal function during the first years of life. What is Known: • There is controversy about which management should be adopted in infants with unilateral ureteropelvic junction obstruction with poor drainage but good differential renal function. What is New: • Long-term follow-up suggests that conservative management can be safely achieved also in unilateral ureteropelvic junction obstruction with poor drainage in more than 60% of cases, even if high-grade hydronephrosis is unlikely to resolve spontaneously and it is often accompanied by a loss of renal function during the first years of life. In our experience, surgical intervention was required in more than 50% of cases before 1 year of life and in all cases before 3 years of life.

Diagnostic accuracy of Onen's Alternative Grading System combined with Doppler evaluation of ureteral jets as an alternative in the diagnosis of obstructive hydronephrosis in children

Introduction

Ureteropelvic junction obstruction (UPJO) is a common congenital anomaly leading to varying degrees of hydronephrosis (HN), ranging from no apparent effect on the renal function to atrophy. Evaluation of these children is based on Diuretic Renal Scintigraphy (DRS) and Ultrasonography (US). Recent studies have suggested that new parameters of conventional and color Doppler ultrasonography (CDUS) may be useful in discriminating which kidneys are obstructed. The present study aims to assess the diagnostic accuracy of such parameters in the diagnosis of obstruction in children with UPJO.

Methods

We evaluated 44 patients (33 boys) with a mean age of 6.53 ± 4.39 years diagnosed with unilateral high-grade hydronephrosis (SFU grades 3 and 4). All underwent DRS and index tests (conventional US and CDUS to evaluate ureteral jets frequency) within a maximum interval of two weeks. Hydronephrotic units were reclassified according to the alternative grading system (AGS) proposed by Onen et al. Obstruction in the DRS was defined as a differential renal function <40% on the affected side and/or features indicating poor drainage function like T1/2 >20 minutes after the administration of furosemide, and a plateau or ascending pattern of the excretion curve.

Results

Nineteen hydronephrotic units (43.1%) were obstructed. Some degree of cortical atrophy—grades 3 (segmental) or 4 (diffuse)—was present in those obstructed units. AGS grades had 100% sensitivity, 76% of specificity and 86.4% of accuracy. The absence of ureteral jets had a sensitivity of 73.68%, a specificity of 100% with an accuracy of 88.6%. When we analyzed the two aspects together and considered obstructed the renal units classified as AGS grade 3 or 4 with no jets, sensitivity increased to 78.9%, accuracy to 92%, remaining with a maximum specificity of 100%. These features combined would allow us to avoid performing DRS in 61% of our patients, leaving more invasive tests to inconclusive cases.

Conclusions

Although DRS remains the mainstay to distinguishing obstructive from non-obstructive kidneys, grade of hydronephrosis and frequency of ureteral jets, independently or in combination may be a reliable alternative in the mostly cases.This alternative approach has high accuracy, it is less invasive, easily reproducible and may play a role in the diagnosis of obstruction in pediatric population.

Vhl deletion in renal epithelia causes HIF-1α-dependent, HIF-2α-independent angiogenesis and constitutive diuresis

One of the earliest requirements for the formation of a solid tumor is the establishment of an adequate blood supply. Clear cell renal cell carcinomas (ccRCC) are highly vascularized tumors in which the earliest genetic event is most commonly the biallelic inactivation of the VHL tumor suppressor gene, leading to constitutive activation of the HIF-1α and HIF-2α transcription factors, which are known angiogenic factors. However it remains unclear whether either or both HIF-1α or HIF-2α stabilization in normal renal epithelial cells are necessary or sufficient for alterations in blood vessel formation. We show that renal epithelium-specific deletion of Vhl in mice causes increased medullary vascularization and that this phenotype is completely rescued by Hif1a co-deletion, but not by co-deletion of Hif2a. A physiological consequence of changes in the blood vessels of the vasa recta in Vhl-deficient mice is a diabetes insipidus phenotype of excretion of large amounts of highly diluted urine. This constitutive diuresis is fully compensated by increased water consumption and mice do not show any signs of dehydration, renal failure or salt wasting and blood electrolyte levels remain unchanged. Co-deletion of Hif1a, but not Hif2a, with Vhl, fully restored kidney morphology and function, correlating with the rescue of the vasculature. We hypothesize that the increased medullary vasculature alters salt uptake from the renal interstitium, resulting in a disruption of the osmotic gradient and impaired urinary concentration. Taken together, our study characterizes a new mouse model for a form of diabetes insipidus and non-obstructive hydronephrosis and provides new insights into the physiological and pathophysiological effects of HIF-1α stabilization on the vasculature in the kidney.

Predictive value of cortical transit time on MAG3 for surgery in antenatally detected unilateral hydronephrosis caused by ureteropelvic junction stenosis

BACKGROUND

In children with antenatally detected hydronephrosis caused by ureteropelvic junction (UPJ) stenosis, the main challenge is preserving renal function by identifying children who require early surgical intervention from those for whom watchful waiting may be appropriate because of the potential for spontaneous resolution without a significant loss of renal function.

OBJECTIVE

To assess the impact of initial cortical transit time (CTT) on technetium-99m mercaptoacetyltriglycerine (MAG3) diuretic renogram on the need for surgery in children with antenatally detected unilateral hydronephrosis caused by UPJ stenosis.

STUDY DESIGN

We retrospectively reviewed the medical records of 33 patients with antenatally detected unilateral hydronephrosis caused by UPJ stenosis who were managed at our institution between 2006 and 2014. Delayed CTT was defined as the absence of activity in the subcortical structures within 3 min of tracer injection on a MAG3 scan. The surgical indication includes symptomatic UPJ stenosis, seriously deteriorating hydronephrosis with parenchymal thinning on serial USG, split renal function <40%, or progressive deterioration of split renal function (>5%) on a MAG3 scan. This study analyzed and compared the initial level of Society for Fetal Urology grade, anteroposterior diameter (APD), split renal function, drainage pattern on a diuretic renogram, and CTT with the need for surgery.

RESULTS

Of the 33 children, 16 were classified into the delayed CTT group and 17 were placed in the normal CTT group. During the follow-up period (mean 31.8 months), surgery was needed in 75.0% (12/16) of patients in the delayed CTT group and in 5.9% (1/17) of those in the normal CTT group. Multivariate analysis showed that delayed CTT on initial MAG3 scan and APD on initial ultrasonography were independent predictive factors of the need for surgery.

DISCUSSION

In this era of conservative management of antenatally detected hydronephrosis caused by UPJ stenosis, it is critical to identify which measurement on an image study is the most reliable for predicting the need for surgery by reflecting functional deterioration. In this study, multivariate analysis revealed that CTT on the initial MAG3 scan was an independent predictive factor of the need for surgery. In addition, CTT showed high negative predictive value for surgical need in children with antenatally detected unilateral hydronephrosis caused by UPJ stenosis.

CONCLUSION

CTT on an initial MAG3 scan may be a useful predictor of the need for surgery in children with antenatally detected unilateral hydronephrosis caused by UPJ stenosis.

Holding Water: Congenital Anomalies of the Kidney and Urinary Tract, CKD, and the Ongoing Role of Excellence in Plumbing

Congenital anomalies of the kidneys and urinary tracts can result in diminished natal kidney function, possibly through common embryologic pathway disruption or as a result of development taking place in the face of disordered 'post-renal' drainage. Impaired conduit and reservoir function present potential for an ongoing assault leading to further deterioration and progression of chronic kidney disease, a risk that extends to adults with these conditions, even after "correction". The drainage and storage aspects of the urinary system that can impact kidney function are reviewed with attention to correctable or manageable problems including: Bladder dysfunction wherein the low pressure storage of urine is compromised requiring the kidney to work against a pressure gradient, the classic post renal failure problem. The kidney in the aftermath of obstruction which may have lost concentrating capacity leading to a tendency to dehydration ('pre-renal' failure) and through polyuria which exacerbates bladder pressure problems. Further there is an added challenge in evaluation for ongoing or reemergent obstruction in a significantly dilated system where the capacious system leads to slow turnover of urine often requiring a ureteral stent or nephrostomy to clearly establish clinical significance of delayed drainage. Stasis where slow urine flow leads to buildup of debris (stone) or potentiates infection. Vessicoureteral reflux which allows for introduction of lower urinary tract bacteria to the kidney and can lead to pyelonephritis. Conditions which combine problems such as posterior urethral valves where the bladder outlet obstruction compromises kidney function potentially impairing concentrating ability, creates bladder compromise often reducing emptying efficiency or elevating bladder storage pressures, as well as dilating the system potentially promoting stasis. Cognizance of the potential for plumbing problems to further kidney deterioration as patients with congenital urinary tract anomalies, even after they have been repaired is incumbent on those caring for these patients as they age. Thoughtful evaluation of those patients in whom kidney compromise maybe aggravated by drainage and storage disorder will optimize native renal function.

Prognostic factors and biomarkers of congenital obstructive nephropathy

Congenital obstructive nephropathy (CON) is the leading cause of chronic kidney disease (CKD) in children. Anomalies of the urinary tract are often associated with abnormal nephrogenesis, which is compounded by obstructive injury and by maternal risk factors associated with low birth weight. Currently available fetal and postnatal imaging and analytes of amniotic fluid, urine, or blood lack predictive value. For ureteropelvic junction obstruction, biomarkers are needed for optimal timing of pyeloplasty; for posterior urethral valves, biomarkers of long-term prognosis and CKD are needed. The initial nephron number may be a major determinant of progression of CKD, and most patients with CON who progress to renal failure reach this point in adulthood, presumably compounded by episodes of acute kidney injury. Biomarkers of tubular injury may be of particular value in predicting the need for surgical intervention or in tracking progression of CKD, and must be adjusted for patient age. Discovery of new biomarkers may depend on "unbiased" proteomics, whereby patterns of urinary peptide fragments from patients with CON are analyzed in comparison to controls. Most promising are the analysis of urinary exosomes (restricting biomarkers to relevant tubular cells) and quantitative magnetic resonance imaging techniques allowing precise determination of nephron number and tubular mass. The greatest need is for large prospective multicenter studies with centralized biomarker sample repositories to follow patients with CON from fetal life through adulthood.

Neonatal and early infancy management of prenatally detected hydronephrosis

Hydronephrosis discovered during prenatal ultrasound will often resolve spontaneously; however, it should be evaluated in the postnatal period in a manner commensurate with its risk of renal injury. Early intervention is appropriate in cases of bladder outlet obstruction or the severely obstructed solitary kidney. In most other cases, it is both safe and reasonable to allow the possibility of spontaneous improvement with the intensity of follow-up based on the severity of the hydronephrosis. Clinical decision making should be a shared process between families and caregivers.

Congenital urinary tract obstruction: the long view

Maldevelopment of the collecting system resulting in urinary tract obstruction (UTO) is the leading identifiable cause of CKD in children. Specific etiologies are unknown; most cases are suspected by discovering hydronephrosis on prenatal ultrasonography. Congenital UTO can reduce nephron number and cause bladder dysfunction, which contribute to ongoing injury. Severe UTO can impair kidney growth in utero, and animal models of unilateral ureteral obstruction show that ischemia and oxidative stress cause proximal tubular cell death, with later development of interstitial fibrosis. Congenital obstructive nephropathy, therefore, results from combined developmental and obstructive kidney injury. Because of inadequacy of available biomarkers, criteria for surgical correction of upper tract obstruction are poorly established. Lower tract obstruction requires fetal or immediate postnatal intervention, and the rate of progression of CKD is highly variable. New biomarkers based on proteomics and determination of glomerular number by magnetic resonance imaging should improve future care. Angiotensin inhibitors have not been effective in slowing progression, although avoidance of nephrotoxins and timely treatment of hypertension are important. Because congenital UTO begins in fetal life, smooth transfer of care from perinatologist to pediatric and adult urology and nephrology teams should optimize quality of life and ultimate outcomes for these patients.

ESPR uroradiology task force imaging recommendations in paediatric uroradiology, part VII: standardised terminology, impact of existing recommendations, and update on contrast-enhanced ultrasound of the paediatric urogenital tract

Our purpose is to harmonise and standardise terminology in paediatric uroradiology, to provide and update recommendations for contrast-enhanced US to standardise imaging and encourage further research, and to assess the impact of the existing recommendations in paediatric urogenital imaging. Based on thorough review of literature and variable practice at several centres and after discussion within urogenital imaging groups as well as with other subspecialties, we propose a standardisation of terminology in urogenital imaging. An update with recommendations on paediatric contrast-enhanced US has been issued based on available literature and reports. Finally, a questionnaire has been used to assess the knowledge, applicability and usefulness of, and the adherence to existing recommendations of the European Society of Paediatric Radiology (ESPR) Uroradiology Task Force. In conclusion, the ESPR is working to improve patient safety and optimise paediatric urogenital imaging. Standardisation of terminology and provision of updated knowledge on contrast-enhanced US in childhood will contribute to this task, ideally reducing the need for invasive or radiating imaging. Not all existing recommendations are commonly known, which limits adherence to these recommendations and the availability of comparable data and evidence for future adaptation of imaging strategies in paediatric uroradiology.

Cortical transit time as a predictive marker of the need for surgery in children with pelvi-ureteric junction stenosis: preliminary study

INTRODUCTION

Postnatal management of prenatally detected hydronephrosis remains controversial. It has been suggested that cortical transit time (CTT) could successfully predict deterioration in children with pelvi-ureteric junction (PUJ) obstruction. We decided to conduct a retrospective study in our hydronephrosis population to evaluate whether initial CTT was significantly correlated with the need for surgery.

PATIENTS AND METHOD

We reviewed the charts of all our patients managed for significant PUJ obstruction (>12 mm) between 2007 and 2010 and determined CTT retrospectively, on the first diuretic scan of each of these patients. We then determined the relationship between initial CTT and the need for surgery.

RESULTS

We identified 37 patients with hydronephrosis (pelvic size >12 mm) of which 26 were diagnosed prenatally. Out of 22 patients with an initial abnormal CTT, 20 underwent surgery. Out of 15 children with a normal initial CTT, 4 underwent surgery (OR 27.5 (IC95%: 4.3-174.9)).

CONCLUSION

Initial CTT could be a reliable prognostic factor for future evolution of renal function in children with hydronephrosis. CTT is easy to determine on diuretic renal scan. A prospective trial is being devised to confirm what role it could have in the management of children with hydronephrosis.

Prediction of the outcome of antenatal hydronephrosis: significance of urinary EGF

BACKGROUND

Down-regulation of epidermal growth factor (EGF) in the renal parenchyma has been demonstrated in children who underwent pyeloplasty due to ureteropelvic junction obstruction (UPJO). Urine levels of EGF were confirmed to parallel this finding before and after surgery. The aim of our study was to evaluate the relationship between urinary EGF (uEGF) concentrations and Society of Fetal Urology (SFU) high-grade hydronephrosis in infants presenting unilateral antenatal hydronephrosis (ANH).

METHODS

This was a prospective study involving 45 infants (33 in the observational group, 12 in the surgical group) who presented with unilateral ANH. Postnatal evaluation included a clinical examination, renal ultrasonography, and voiding cystourethrography. Diuretic renal scans were performed in infants with an initial SFU grade 3 or 4 hydronephrosis or increasing hydronephrosis during follow-up. Pyeloplasty was performed when a well-tempered renogram showed an obstructive drainage curve with a half-life of >20 min and/or an obstructive washout curve pattern during the diuretic phase. We studied the longitudinal changes in SFU hydronephrosis grade and uEGF in each group and compared concentration levels at three time points in both groups. The enzyme-linked immunosorbent assay (ELISA) method was used to measure EGF concentrations in the urine. The results were normalized with urinary creatinine (Cr).

RESULTS

During the first 6 months, from 6 to 12 months, and in the second year of life, median SFU hydronephrosis grade and uEGF levels were 2, 2 (p = 0.015), and 1 (p < 0.01), and 50, 59 (p = 0.015), and 69.5 ng/mg Cr (p < 0.01), respectively, in the observational group. In the first 6 months, preoperatively and at 3-12 months postoperatively, the median SFU hydronephrosis grade and uEGF levels were 4, 4, and 3 (p > 0.05), and 38, 46, (p > 0.05), and 55 ng/mg Cr (p < 0.01), respectively, in the surgical group. uEGF levels in the first 6 months of life were significantly lower in the surgical group than in the observational group (p < 0.01). Patients in the observational group with SFU grade 3-4 hydronephrosis showed higher uEGF levels than those in the surgical group with SFU grade 3-4 in (p = 0.048).

CONCLUSIONS

Urinary EGF changes over time are associated with inverse changes in SFU hydronephrosis grade, which suggests a role for uEGF as a predictive marker of worsening hydronephrosis grades in infants with ANH. uEGF in the first 6 months of life may predict the need for surgery in infants with ANH.

Effects of melatonin on partial unilateral ureteral obstruction induced oxidative injury in rat kidney

AIM

This experimental study was designed to produce ischemia-reperfusion injury in rat kidney by performing partial unilateral ureteral obstruction (PUUO) and investigated the effects of melatonin on the levels of oxidative injury parameters.

MATERIALS AND METHODS

Twenty-four adult male rats were randomly divided into three groups as follows; control group (Group 1); only nephrectomy and blood (5 ml) drawn from vena cava inferior, PUUO group (Group 2); PUUO (10 days)+ipsilateral nephrectomy after recovery of PUUO+blood from vena cava inferior VCI, melatonin treated group (Group 3); PUUO (10 days)+melatonin (1/2 hr before release, 50 mg/kg, ip)+ipsilateral nephrectomy after recovery of PUUO+blood from VCI. The left ureter was embedded into the psoas muscle to create PUUO. After 10 days, PUUO was recovered and ipsilateral nephrectomies were performed for biochemical analysis of superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), glutathione peroxidase (GSH-Px), and protein carbonyl (PC) in the tissues and blood was drawn from inferior vena cava to study the same parameters in systemic circulation. The results were compared statistically.

RESULTS

The blood levels of MDA, NO, and PC were increased in the PUUO group in comparison to the sham-operated group (P<0.05). Melatonin treatment reduced MDA, NO, and PC levels in blood after PUUO recovery, but statistically significance consisted only for MDA and NO (P<0.05). The antioxidant enzyme activities (SOD, GSH-Px) were increased in the PUUO group (P<0.05). Melatonin treatment reduced SOD and GSH-Px activities in comparison with the sham-operated control group (P<0.05). Similarly, renal tissue levels of MDA, NO, and PC were increased in the PUUO group in comparison with the sham-operated group (P<0.05). Melatonin treatment ameliorated MDA, NO, and PC levels in renal tissue after PUUO recovery only MDA was statistically significant (P<0.05). Antioxidant enzyme activities (SOD, CAT, and GSH-Px) were increased in the PUUO group. Melatonin treatment caused reduction in SOD, CAT, and GSH-Px activities in comparison to the sham-operated control group (P<0.05).

CONCLUSION

The results of this study showed that experimentally induced PUUO caused oxidative stress in rat kidney and melatonin treatment reduced oxidative stress and therefore may have a preventive effect on PUUO induced oxidative kidney damage in rats.

Renal axis deviation in urinary tract abnormalities of children: the role of renal scintigraphy

BACKGROUND

Urinary tract pathologies are common in children. Previous reports suggested a relationship between some renal pathologies and renal anatomic variations. This study evaluates the effect of different urinary tract abnormalities on scintigraphic renal long axis.

METHODS

Children referred to our nuclear medicine department for Tc-99m dimercaptosuccinic acid and/or Tc-99m N,N-ethylenedicysteine renal scintigraphies were entered consecutively. Presence of single, ectopic, or fused kidneys, extrarenal pathologies altering renal long axis, and history of renal surgery or advanced renal disease were used as exclusion criteria. If indicated, patients were assessed for vesicoureteral reflux (VUR). Long renal axis of each kidney was drawn with a line passing through the kidney's upper and lower poles using posterior image. The angle between this axis and patient's longitudinal body axis was defined as "renal angle." After defining age-groups, "age-corrected renal angle" was calculated.

RESULTS

A total of 311 cases (622 kidney units) entered the study (183 females, 128 males). Mean age was 41.8 months. Mean "renal angle" was 11.7, 11.9, 14.1, 17.6, 28.5, 16.7, and 19.2 degrees in normal, mild, moderate, and severe VUR, high-grade ureteropelvic junction (UPJ) obstruction, nonobstructive pelvic dilatation, and ureterovesical junction obstruction, respectively (P = 0.000). Applying receiver operating characteristic analysis and using ultrasonography as the gold standard, renal angle deviation of 13.75 degrees led to the sensitivity of 74.6% and specificity of 70.7% to detect pyelocalyceal system dilatation. Using a "renal angle" cutoff value of 18.7 degrees, 85% sensitivity and 85% specificity were achieved for the diagnosis of high-grade UPJ obstruction. Using "age-corrected renal angle," a cutoff value of 3.9 degrees was consistent with 60% sensitivity and 73% specificity for the diagnosis of severe VUR.

CONCLUSION

Considerable renal axis deviation is noted in patients with UPJ obstruction and severe VUR in children. Measurement of "renal angle" provides indirect but useful clues to the presence of urinary tract pathologies. Renal scintigraphy is a useful tool for drawing renal axis and measuring "renal angle," potentially making it useful for prediction of urinary tract system abnormalities.

Complications and long-term outcome of primary obstructive megaureter in childhood

We assessed the clinical outcome of 49 children with 56 primary obstructive megaureters (POM) treated with the primarily conservative approach recommended by the 2001 German consensus guidelines. POM occurred more often in boys (71%) and on the left side (67%). Forty-three POM (77%) were treated conservatively. Four kidneys underwent immediate surgery and nine of 52 kidneys managed primarily conservatively worsened subsequently, requiring surgery. Urinary tract infections (UTI) were the most common complication (mean 1.3 per patient), with frequent hospital admission (45%). During the first year of life, the incidence of UTIs was 55% less during prophylactic antibiotic treatment (0.94 vs.0.42 UTIs per year, p < 0.05). Spontaneous regression occurred in 80% of POMs with dilated non-obstructive renogram, but in <20% with intermediate or relevant obstruction. All megaureters with <8.5 mm sonographic diameter regressed, but none over 15 mm. Eight patients had a poor outcome (partial kidney function <40% (n = 6), renal atrophy (n = 3)), but in seven of the patients, these findings were already present postnatally. In summary, the long-term outcome of POM appears favorable with mainly conservative treatment. UTI as the most common complication was 55% lower with antibiotic prophylaxis in infants. Adverse outcome was more closely related to congenital kidney hypoplasia than to degree of obstruction.

Obstructive diseases of the urinary tract in children: lessons from the last 15 years

Imaging urinary tract obstruction is a common query in paediatric uroradiology. With the advent of a more conservative treatment approach, the task of imaging today is to distinguish as early as possible those kidneys that do not require surgery, from those that will deteriorate and lose function and/or growth potential and thus benefit from surgery. At present, in spite of significant advancements in imaging and the introduction of diuretic paediatric MR-urography, there is still no reliable a-priori pro-futuro assessment. Thus, repeated follow-up imaging is often necessary for monitoring. Imaging usually starts with US; the major additional complementary and more function-oriented tools are diuretic renal scintigraphy and MR-urography. The frequency and timing as well as the detailed protocol vary within institutions, partly because of differences in the criteria that are used for indicating surgery. Intra-venous urography (IVU) for obstruction has practically vanished apart from for a few exceptions, and the "Whitaker" test is today seldom performed, being reserved for complicated cases.

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.

Robotic correction of Östling folds as a rare cause of ureteropelvic junction obstruction in children

Östling folds are considered to be normal variants of ureteral growth at a quicker rate than body lengthening and, therefore, have been reported to be of no clinical significance. We report a robotic correction of the first documented cases of Östling folds causing a persistent ureteroplevic junction obstruction in children.

Normal differential renal function does not indicate a normal kidney after partial ureteropelvic obstruction and subsequent relief in 2-week-old piglets

PURPOSE

We investigated the functional consequences of relieving ureteric obstruction in young pigs with experimental hydronephrosis (HN) induced by partial unilateral ureteropelvic obstruction.

MATERIALS AND METHODS

Three groups of animals were followed from the age of 2 weeks to the age of 14 weeks: Eight animals had severe or grades 3-4 HN throughout the study. Six animals had relief of the obstruction after 4 weeks. Six animals received sham operations at both ages. Morphological and functional examinations were performed at age 6 weeks and again at age 14 weeks and consisted of magnetic resonance imaging (MRI), technetium-diethylenetriaminepentaaceticacid ((99m)Tc-DTPA) renography, renal technetium-dimercaptosuccinicacid ((99m)Tc-DMSA) scintigraphy, and glomerular filtration rate (GFR) measurement.

RESULTS

After relief of the partial obstruction, there was reduction of the pelvic diameter and improvement of urinary drainage. Global and relative kidney function was not significantly affected by either obstruction or its relief. Renal (99m)Tc-DMSA scintigraphy showed a change in both the appearance of the kidney and a change in the distribution within kidneys even after relief of obstruction.

CONCLUSION

This study shows that partial ureteric obstruction in young pigs may be associated with little effect on global and differential kidney function. However, even after relief of HN, the distribution of (99m)Tc-DMSA in the kidney remains abnormal suggesting that a normal differential renal function may not represent a normal kidney.

Diagnostic accuracy of color Doppler sonographic study of the ureteric jets in evaluation of hydronephrosis

OBJECTIVE

Hydronephrosis (HN) and obstruction are closely associated, but upper urinary tract dilatation can occur without significant obstruction. Despite some pitfalls, conventional ultrasonography and diuretic renography (DR) are the main means of evaluation of HN in children. Recent reports have demonstrated color Doppler ultrasonography (CDUS) to reliably identify ureteric jets in the bladder. The aim of this study was to evaluate this method as a diagnostic tool to distinguish obstructive from non-obstructive dilatations of the upper tract.

METHODS

We evaluated 51 patients (37 boys and 14 girls), aged 3 months to 14 years (median 4 years), who presented with unilateral grade III and IV hydronephrosis with suspicion of pyeloureteral junction obstruction. All patients underwent DR and evaluation of ureteric jets by transverse CDSG of the bladder within a maximum of 2 weeks. Obstruction was considered in the DR when the hydronephrotic unit showed a differential renal function of less than 40%, or when symptomatic intermittent renal colic was present in older children. The number of ureteric jets was counted over a 5-min period and the frequency calculated for each ureteral orifice. Relative jet frequency (RJF) was defined as frequency of the hydronephrotic side divided by total ureteric jet frequency. Receiver-operating characteristic (ROC) plots were constructed to determine the best cut-off for RJF, in order to identify renal units with obstructive hydronephrosis.

RESULTS

Twenty-three (45.1%) hydronephrotic units were considered obstructed. The mean RJF differed between obstructive (0.09+/-0.15) and non-obstructive hydronephrosis (0.42+/-0.11) (p<0.001). ROC analysis revealed that RJF <0.25 was the best threshold, and correctly discriminated obstruction in 91.2% of the children with a sensitivity of 87% (95% CI 78.6-98.2%) and specificity of 96.4% (95% CI 87.8-99%). The positive likelihood ratio was 24.3 and the area under the ROC curve was 0.92 (95% CI 0.86-0.98).

CONCLUSIONS

RJF <25% was found to be a good indicator of obstruction in children with unilateral hydronephrosis. CDUS evaluation of ureteric jets is an easy and non-invasive method that can be used as an initial diagnostic tool, and in follow-up cases, to differentiate obstructed from non-obstructed hydronephrosis in the pediatric population.

International Scientific Committee of Radionuclides in Nephrourology (ISCORN) consensus on renal transit time measurements

This report is the conclusion of the international consensus committee on renal transit time (subcommittee of the International Scientific Committee of Radionuclides in Nephrourology) and provides recommendations on measurement, normal values, and analysis of clinical utility. Transit time is the time that a tracer remains within the kidney or within a part of the kidney (eg, parenchymal transit time). It can be obtained from a dynamic renogram and a vascular input acquired in standardized conditions by a deconvolution process. Alternatively to transit time measurement, simpler indices were proposed, such as time of maximum, normalized residual activity or renal output efficiency. Transit time has been mainly used in urinary obstruction, renal artery stenosis, or renovascular hypertension and renal transplant. Despite a large amount of published data on obstruction, only the value of normal transit is established. The value of delayed transit remains controversial, probably due to lack of a gold standard for obstruction. Transit time measurements are useful to diagnose renovascular hypertension, as are some of the simpler indices. The committee recommends further collaborative trials.

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.

MR urography evaluation of obstructive uropathy

Hydronephrosis and the evaluation of obstructive uropathy are the most common indications for MR urography in our practice. Typically our patients fall into one of two groups: infants with antenatal hydronephrosis and older children who present with abdominal pain, hematuria or urinary tract infection. Obstruction in children is usually chronic and partial. Intermittent episodes of increased pressure occur when the urine production exceeds the capacity for drainage. MR urography uses a fluid and diuretic challenge to assess the hydronephrotic kidney. High-quality anatomic images provide a morphologic assessment of the hydronephrotic system. Although it is relatively straightforward to determine if a system is not obstructed on the basis of the renal transit time (RTT), no single parameter is adequate to fully characterize obstruction. By evaluating the changes in signal intensity in the renal parenchyma following contrast administration, the hydronephrotic systems are classified as compensated or decompensated. Delayed RTT and the presence of urine-contrast levels indicate stasis. Calyceal transit time and the difference between the volumetric and the Patlak differential renal function (vDRF-pDRF) are measures of the physiologic changes within the kidney. Additionally, MR urography provides prognostic information by assessing the quality of the renal parenchyma and identifying uropathy preoperatively. MR urography combines both anatomic and functional information in a single test and is capable of providing a comprehensive evaluation of obstructive uropathy that could ultimately help select those patients most likely to benefit from surgical intervention.

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.

Dynamic Magnetic Resonance Nephrography

PURPOSE

In this volunteer study, 2 navigator-gated strongly T1-weighted saturation-recovery (SR) sequences, a turbo fast low angle shot (TurboFLASH) and a new true fast imaging in steady precession (TrueFISP) readout technique, were compared for suitability in dynamic magnetic resonance nephrography.

MATERIALS AND METHODS

Ten healthy volunteers (mean age 26.1 +/- 3.6) were equally divided into 2 subgroups. After bolus-injection of 3.75 mL of gadobutrol (approximately 0.05 mmol/kg body weight), slightly obliqued coronal single-slice images of the kidneys were recorded every 4-5 seconds during free breathing using 1 of the 2 sequences. Time-intensity curves were determined from manually drawn regions-of-interest over the kidney parenchyma. Both sequences were subsequently evaluated with regard to linearity of signal, signal to noise ratio (SNR), and time-dependent behavior of signal intensity curves.

RESULTS

: The TurboFLASH readout showed better linearity of the signal behavior as compared with the TrueFISP technique (TurboFLASH: no deviation from linearity down to T1 = 400 milliseconds; TrueFISP at T1 = 700 milliseconds: 12% deviation, at T1 = 400 milliseconds: 19%). The time-intensity curves of the TrueFISP sequence exhibited distinctly lower variability than the TurboFLASH approach. The SNR increased with TrueFISP by 3.4 +/- 0.5-fold for native renal parenchyma and by 3.3 +/- 0.9 for contrast-enhanced renal parenchyma. For split renal function evaluation, the linear regression to the signal increase in the first minutes after the first pass could be performed with higher reliability using the TrueFISP technique (increase of correlation coefficient by 17.1%).

CONCLUSION

A SR navigator-gated TrueFISP sequence seems most favorable for dynamic magnetic resonance nephrography due to the high signal yield and low curve variability.