Urinary levels of the renal tubular enzyme N-acetyl-beta-D-glucosaminidase in unilateral obstructive uropathy

Effects of the beta-blocker carvedilol on arrhythmia and long-term clinical outcomes in benign prostate hypertrophy patients

Benign prostatic hypertrophy (BPH) is associated with autonomic dysfunction and sympathetic nervous system mediated by the alpha receptor. However, limited data exist regarding the effects of the beta-blocker (BB) carvedilol on arrhythmia and urologic outcomes in BPH patients. Our database of patients diagnosed with BPH from 2015 to 2020 was used to obtain echocardiography and electrocardiogram data. Inclusion criteria were BPH patients taking BBs. International Prostate Symptom Score questionnaire were used to evaluate the urinary symptoms and quality of life. Among 448 patients with BPH (69.2 ± 10.9 years) taking BBs, 219 patients took carvedilol (48.9%) and 229 patients took a non-carvedilol BB (51.1%; bisoprolol, 184 patients, 80% or nebivolol, 45 patients, 20%). Difference in the baseline characteristics was not observed. During the median 36-month follow-up, a lower incidence of arrhythmic events (P = .029), total urologic events (P < .001), and less use of additive alpha-blocker was observed in the carvedilol group (P = .022). In multivariate analysis, less carvedilol use (P = .019), heart failure (P < .001), stroke (P < .001), and cardiomyopathy (P = .046) were independent risk factors for arrhythmic events. In addition, less carvedilol use (P = .009) and older age (P = .005) were independent risk factors for urologic events based on BB type at the median 36-month follow-up. The use of carvedilol was associated with less arrhythmic events in BPH patients with palpitation and decreased the incidence of urologic events in BPH compared with the use of non-carvedilol BBs in long-term follow-up.

Reflux nephropathy and scarring nephropathy: So close and yet so different

OBJECTIVES

Reflux nephropathy is a radiologic condition commonly used to express the existence of renal morphological lesions in patients who have or had vesicoureteral reflux (VUR). This morphological concept is used based on the image data collected, without conducting basic complementary renal function studies. The present study was designed to demonstrate that patients with active VUR present different functional renal alterations from those shown by patients with disappeared VUR.

METHODS

Longitudinal descriptive retrospective analysis including 89 children (46M, 43F) with VUR diagnosis through a standard voiding cystourethrogram (VCUG). The basic renal function tests collected were the maximum urinary osmolality (UOsm) and the urinary albumin/creatinine and NAG/creatinine ratios. The data collected corresponded to two moments, when VUR was diagnosed and when it had already disappeared.

RESULTS

Quantitative differences were verified in the three functional parameters when comparing those corresponding to both moments of the study. In the qualitative analysis, in relation to the intensity of the VUR, differences were observed in UOsm at diagnosis and in the albumin/creatinine ratio once the VUR had cured. At this last moment, a significant increase in the albumin/creatinine ratio was observed in patients with loss of renal parenchyma in relation to those without residual morphological lesions.

CONCLUSIONS

Concentrating ability defect is the most frequent finding in children with active reflux (true reflux nephropathy), whereas the most frequent functional disturbance found, once VUR has cured, is an increase in urinary albumin excretion, related to parenchymal damage. The term dysplastic-scarring nephropathy, could be more appropriate for patients with residual morphological lesions and impaired renal function, once VUR is cured.

[Reflux nephropathy and scarring nephropathy: So close and yet so different]

OBJECTIVES

Reflux nephropathy is a radiologic condition commonly used to express the existence of renal morphological lesions in patients who have or had vesicoureteral reflux (VUR). This morphological concept is used based on the image data collected, without conducting basic complementary renal function studies. The present study was designed to demonstrate that patients with active VUR present different functional renal alterations from those shown by patients with disappeared VUR.

PATIENTS AND METHODS

Longitudinal descriptive retrospective analysis including 89 children (46M, 43F) with VUR diagnosis through a standard voiding cystourethrogram (VCUG). The basic renal function tests collected were the maximum urinary osmolality (UOsm) and the urinary albumin/creatinine and NAG/creatinine ratios. The data collected corresponded to two moments, when VUR was diagnosed and when it had already disappeared.

RESULTS

Quantitative differences were verified in the three functional parameters when comparing those corresponding to both moments of the study. In the qualitative analysis, in relation to the intensity of the VUR, differences were observed in UOsm at diagnosis and in the albumin/creatinine ratio once the VUR had cured. At this last moment, a significant increase in the albumin/creatinine ratio was observed in patients with loss of renal parenchyma in relation to those without residual morphological lesions.

CONCLUSIONS

Concentrating ability defect is the most frequent finding in children with active reflux (true reflux nephropathy), whereas the most frequent functional disturbance found, once VUR has cured, is an increase in urinary albumin excretion, related to parenchymal damage. The term dysplastic-scarring nephropathy, could be more appropriate for patients with residual morphological lesions and impaired renal function, once VUR is cured.

The use of urinary osmolality to evaluate postoperative renal function in children with ureteropelvic junction obstruction

INTRODUCTION

Split renal function measured in a diuretic renogram is the most popular tool in initial assessment and follow-up of patients with ureteropelvic junction obstruction (UPJO). This study aims to evaluate the use of maximum urinary osmolality after desmopressin administration (DDAVP) to detect renal dysfunction.

PATIENTS AND METHODS

56 children (33 males, 23 females) diagnosed with UPJO underwent quantification of the maximum urinary osmolality (UOsm) at diagnosis. 41 of these children (28 males, 13 females) underwent surgery for UPJO and quantification of the UOsm before and after the surgical intervention (six to 18 months postoperatively) and were included in this longitudinal study.

RESULTS AND DISCUSSION

At diagnosis, UOsm measured after desmopressin administration was abnormal in 64% of patients. After surgical intervention, this rate decreased to 53%. At initial assessment, high creatinine levels were found in 32% of infants younger than one year of age. Albumin/Cr and NAG/Cr ratios were elevated in 12% and 7% of cases, respectively. After surgical intervention, an improvement in the NAG/creatinine ratio and creatinine levels was observed. Preoperative split renal function of the affected kidney was less than 45% in 39% of cases, normal in 44%, and greater than 55% in 17%; in these three subgroups, no differences in renal function markers were found.

CONCLUSIONS

The most sensitive parameter to detect alterations in renal function in children with UPJO is the UOsm and, therefore, the most useful in the follow-up after surgery. No correlation was found between other functional and morphological parameters obtained on renal ultrasound and renogram.

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.

Can urinary biomarkers detect obstruction defined by renal functional loss in antenatal hydronephrosis?

INTRODUCTION

Diagnosing obstruction and thus, assessment of need for surgery in the management of antenatal hydronephrosis may be challenging. Current diagnostic tests are not capable of indicating which patients are at risk for obstructive nephropathy. Biomarkers may play an important role in distinguishing these patients.

OBJECTIVE

The aim of this study is to evaluate if urinary biomarkers could differentiate obstruction (OBS) from non-obstructive dilation (NOD) in patients with antenatal hydronephrosis (AH) that underwent pyeloplasty due to loss of differential renal function (DRF).

STUDY DESIGN

Children with a history of AH and postnatal anteroposterior (AP) diameter ≥15 mm were included in this study of prospectively collected data between 2010 and 2018. The OBS group included patients who underwent pyeloplasty due to solely ≥10% subsequent decrease in DRF on a MAG-3 scan during follow-up. Patients with stable or improving hydronephrosis with no significant reduction in ipsilateral DRF (<10%) during follow-up formed the NOD group. Healthy children with no history of AH and a normal urinary ultrasound were taken as the control group. Urinary IP-10, MCP-1, KIM-1, NGAL, and Ca19-9 levels using ELISA were measured. In the OBS group, urine samples were obtained preoperatively and at 3rd post operative-month whereas in the NOD and control groups, samples were collected at the time of enrollment.

RESULTS

There were 24 children in the OBS and 27 children in the NOD groups. The control group consisted of 27 healthy children. The pre-operative bladder urine levels of biomarkers of the OBS group were significantly higher than in the NOD and control group (p < 0.05, for all). In terms of differentiating OBS from NOD, results of ROC analyses for the given cut-off values were as follows: 135.06 ng/mgCr (sensitivity 75%; specificity 66%, AUC = 0.735) for IP-10, 0.89 ng/mgCr (sensitivity 79.2%; specificity 88%, AUC = 0.802) for KIM-1, 367.65 pg/mgCr (sensitivity 62.5%; specificity 52%, AUC = 0.660) for MCP-1, 16.15 ng/mgCr (sensitivity 70.8%; specificity 70.4%, AUC = 0.669) for NGAL, and 55.5 U/mgCr (sensitivity 75%; specificity 66%, AUC = 0.676) for Ca 19-9. Moreover, when KIM-1 was combined with IP-10 and Ca19-9, sensitivity and specificity levels were 83% and 85% (AUC = 0.919), respectively.

CONCLUSION

In this novel study, which focused on scintigraphic DRF loss, KIM-1 was the most successful among all the biomarkers evaluated. Combination of IP-10, Ca19-9 and KIM-1 resulted increased diagnostic ability.

Roles Played by Biomarkers of Kidney Injury in Patients with Upper Urinary Tract Obstruction

Partial or complete obstruction of the urinary tract is a common and challenging urological condition caused by a variety of conditions, including ureteral calculi, ureteral pelvic junction obstruction, ureteral stricture, and malignant ureteral obstruction. The condition, which may develop in patients of any age, induces tubular and interstitial injury followed by inflammatory cell infiltration and interstitial fibrosis, eventually impairing renal function. The serum creatinine level is commonly used to evaluate global renal function but is not sensitive to early changes in the glomerular filtration rate and unilateral renal damage. Biomarkers of acute kidney injury are useful for the early detection and monitoring of kidney injury induced by upper urinary tract obstruction. These markers include levels of neutrophil gelatinase-associated lipocalin (NGAL), monocyte chemotactic protein-1, kidney injury molecule 1, N-acetyl-b-D-glucosaminidase, and vanin-1 in the urine and serum NGAL and cystatin C concentrations. This review summarizes the pathophysiology of kidney injury caused by upper urinary tract obstruction, the roles played by emerging biomarkers of obstructive nephropathy, the mechanisms involved, and the clinical utility and limitations of the biomarkers.

Cortical transit time: understanding utility and pitfalls in children with pelviureteric junction obstruction

INTRODUCTION

Delayed cortical transit time (CTT) has been recently studied and proposed as a parameter that can predict the need for surgery in children with pelviureteric junction obstruction (PUJO).

AIM

The aim of this study was to study the change in CTT, after surgery, in children with PUJO and to correlate CTT with intrapelvic pressure of the kidney.

MATERIAL AND METHODS

A prospective study was performed, and all children who underwent pyeloplasty from January 2016 to December 2017 were included. Pre-operative and postoperative renal ultrasonography and Technetium-99m mercaptoacetyltriglycerine Tc-MAG3 renal scintigraphy were performed. Cortical transit time was measured by a visual method by two different observers. The renal intrapelvic pressure of the kidney was also measured during surgery after giving a diuretic to replicate the diuresis induced during the renal scan. The correlation was studied between the pre-operative CTT and intrapelvic pressures and between the pre-operative CTT and the renal function of the affected kidney.

RESULTS

Thirty-one children were included in the study. The median age of children who underwent surgery was 50 months (2-168). In 71% of patients, the CTT was prolonged before surgery, whereas only 22.5% had delayed CTT after surgery. The mean CTT before surgery was 226.1 ± 74.8 s and decreased to 165.4 ± 55.9 s after surgery (p= <0.001). The mean intrapelvic pressure was 21 ± 7.5 cm H₂O. There was no correlation noted between the intrapelvic pressure and the CTT. A significant negative correlation was noted between the CTT and the different renal function of the kidney.

DISCUSSION

This is the first prospective study that studies the changes in CTT after surgery. Only retrospective studies had been conducted to date which concluded that CTT was delayed in most of the patients who had been operated. It has been proposed that the prolonged CTT is due to raised pressure in the kidney secondary to obstruction. This study did not find any correlation between the pressure and CTT. The significant negative correlation between CTT and renal function also emphasizes the need to take the renal function into consideration before interpreting and using the absolute value of CTT for guiding treatment.

CONCLUSION

Cortical transit time assessment by the visual method is a useful parameter in the management of children with PUJO. There is a significant improvement in CTT after surgery.

Renal tubular markers as screening tools for severe vesicoureteral reflux

Severe (grades IV and V) vesicoureteral reflux (VUR) is a risk factor for acute pyelonephritis, renal scars, and renal failure. This study evaluates albumin and N-acetylglucosaminidase (NAG) urinary excretion, and renal concentrating ability as screening tools to select patients for voiding cystourethrogram (VCUG). Children (111 M, 52 F) aged 10.97 ± 21.17 months (mean + SD), diagnosed with UTI, and who had undergone renal ultrasound and a VCUG, underwent a desmopressin test and had albumin/creatinine and NAG/creatinine urinary excretion measured. Urine osmolality was significantly lower in 27 children with severe VUR (375.3 ± 171.8 mOsm/kg; mean + SD) compared to 100 patients with normal VCUG (611.5 ± 175.8 mOsm/kg), p < 0.001, and to 36 patients with VUR grades I to III (636.2 ± 180.2 mOsm/kg), p < 0.001. NAG/creatinine ratio was significantly elevated in 20 children with severe VUR (26.4 (28.3) U/g); median and interquartile range compared to 67 children with normal VCUG (10.8 (17.9) U/g), p = 0.003, and to 20 patients with VUR grades I to III (7.6 (21.1) U/g), p = 0.009.Conclusions: Urinary osmolality is significantly decreased and urinary excretion of NAG is significantly increased in patients with severe VUR. These tests could select patients for VCUG to assess for severe VUR. What is Known: • Severe vesicoureteral reflux (SVUR) may contribute to renal damage. Severe vesicoureteral reflux is diagnosed by voiding cystourethrogram and represents about 10% of all patients with VUR. Currently, there are no reliable tests used prior to VCUG to help on the decision of obtaining a VCUG to diagnose SVUR. What is New: • This study shows that renal tubular markers (concentrating ability and N-acetylglucosaminidase (NAG) excretion) are useful tests prior to voiding cystourethrogram to screen for severe vesicoureteral reflux. • This study suggests the use of renal concentrating ability and urinary N-acetylglucosaminidase (NAG) excretion to screen for severe vesicoureteral reflux before requesting a voiding cystourethrogram.

A Novel Biomarker for Acute Kidney Injury, Vanin-1, for Obstructive Nephropathy: A Prospective Cohort Pilot Study

Background: Vanin-1 is a novel acute kidney injury (AKI) biomarker that has not been clinically investigated as a biomarker for obstructive nephropathy. This study investigated the diagnostic value of vanin-1 as a biomarker for adult obstructive nephropathy by comparing it to existing AKI biomarkers. Methods: A total of 49 patients, 21 controls, and 28 hydronephrosis (HN) cases were assessed. AKI biomarkers in bladder (BL) urine and renal pelvic (RP) urine in the HN group were compared to each BL marker in the control group. In a subgroup of cases receiving interventions for obstructive nephropathy, the BL values of each biomarker were assessed after the intervention. Results: RP vanin-1 levels were significantly higher while BL vanin-1 levels were marginally higher in the HN group than in the control group. The area under the receiver operating characteristics curve values for RP and BL vanin-1 were 0.9778 and 0.6386, respectively. In multivariate analyses, BL vanin-1 and N-acetyl-β-D-glucosaminidase (NAG), but not kidney injury molecule-1 (KIM-1) or neutrophil gelatinase-associated lipocalin (NGAL), were independent factors for predicting the presence of HN. In cases receiving interventions, vanin-1 decreased significantly from 1 week after the intervention in cases of moderate to severe obstructive nephropathy compared to RP values at baseline. Conclusion: Urinary vanin-1 is a useful biomarker to detect and monitor the clinical course of obstructive nephropathy.

The Diagnostic Role of Urinary N-Acetyl-β-D-glucosaminidase (NAG) Activity in the Detection of Renal Tubular Impairment

The kidney function can be assessed by a number of methods. The urinary excretion of enzymes, in particular N-acetyl-β-D-glucosaminidase (NAG), is considered a relatively simple, cheap, fast and non-invasive method in the detection and follow-up of renal tubular function under various conditions. The determination of urinary NAG provides a very sensitive and reliable indicator of renal damage, such as injury or dysfunction due to diabetes mellitus, nephrotic syndrome, inflammation, vesicoureteral reflux, urinary tract infection, hypercalciuria, urolithiasis, nephrocalcinosis, perinatal asphyxia, hypoxia, hypertension, heavy metals poisoning, treatment with aminoglycosides, valproate, or other nephrotoxic drugs. This paper gives an overview of the current use of urinary NAG in the detection of renal injury.

Evaluation of Renal Histopathological Changes, as a Predictor of Recoverability of Renal Function Following Pyeloplasty for Ureteropelvic Junction Obstruction

Background:

Pyeloplasty is a widely accepted treatment for ureteropelvic junction obstruction (UPJO). However, the renal function recoverability after pyeloplasty is still a matter of debate. Different parameters have been used to predict renal functional recoverability after corrective surgery, with conflicting results.

Objectives:

In this study, renal biopsy was carried on a series of cases of UPJO, during pyeloplasty, to study the extent of histological alterations in renal parenchyma, as a result of obstruction, and its predictive value in renal function recoverability after pyeloplasty.

Patients and Methods:

We retrospectively analyzed the renal biopsy obtained during pyeloplasty in 53 adult patients. Histopathological changes were graded on a scale of 1 to 3, according to their severity, and compared with the differential renal function (DRF) revealed on the preoperative and postoperative follow up diethylene triamine pentaacetic acid (DTPA) renal scan. A Fischer’s t test was used to evaluate statistical differences between values.

Results:

This study showed a linear relationship between the severity of histological changes and renal function recovery, after pyeloplasty. Out of 24 obstructed renal units (ORU), with minimal histopathological changes (grade I), 21 ORU (87.5%), with > 35% DRF preoperatively, showed significant improvement in renal function after 12 months of pyeloplasty (P < 0.05). On the other hand, all kidneys (n = 29) with moderate to severe obstructive changes (grade II and III) had minimal improvement in DRF, after pyeloplasty, which was clinically insignificant (P > 0.05). Renal function deterioration after pyeloplasty was not observed in any of the cases.

Conclusions:

The severity of pathological changes in renal parenchyma, due to UPJO, is a good predictor of renal function recoverability, after pyeloplasty. The ORUs, with DRF > 35%, usually have normal (grade I) renal biopsy and might be expected to present better functional recoverability after pyeloplasty.

The roles of serum and urinary carbohydrate antigen 19-9 in the management of patients with antenatal hydronephrosis

INTRODUCTION

Serum carbohydrate antigen (CA) 19-9 has been clinically applied as a valuable tumor marker for pancreatic and gastrointestinal carcinoma. CA 19-9 is expressed in normal excretory epithelium tissues. Increased CA 19-9 has also been observed in uroepithelial tumors as well as in nonmalignant conditions including hydronephrosis secondary to ureteral stones.

OBJECTIVE

The purpose of this article is to evaluate the role of urinary CA 19-9 as a non-invasive biomarker in the postnatal differentiation of obstructive and non-obstructive hydronephrosis in patients with unilateral antenatal hydronephrosis.

STUDY DESIGN

Infants with isolated renal pelvic dilatation, defined as the presence of anteroposterior pelvic diameter (APPD) equal to or greater than 7 mm based on antenatal ultrasound after 28 weeks' gestation, underwent systematic investigation for uropathies and were prospectively followed up. The pyeloplasty group consisted of 17 patients with ureteropelvic junction (UPJ) obstruction who had undergone pyeloplasty. The non-obstructive dilatation (NOD) group consisted of 17 patients with non-obstructive hydronephrosis, and the control group consisted of 21 healthy children. Commercial enzyme-linked immunosorbent assay (ELISA) kits were used to measure the urinary and serum CA 19-9 levels. In both hydronephrosis groups (pyeloplasty and non-obstructive dilatation), the correlations between urinary and serum CA 19-9 levels with the anteroposterior pelvic diameter measured at the third trimester and the postnatal initial evaluation and differential renal function were investigated.

RESULTS

The initial median urinary CA 19-9 levels were significantly greater in children who underwent pyeloplasty than in both the non-obstructive hydronephrosis (143 ± 38 vs. 68 ± 23, respectively; p = 0.007) and the healthy control groups (143 ± 38 vs. 13 ± 3, respectively; p = 0.001) (Figure). Three months after surgery, the urinary CA 19-9 levels had decreased significantly according to the preoperative levels in the pyeloplasty group (143 ± 38 vs. 55 ± 16, p = 0.039). In both the pyeloplasty and NOD groups, there was a correlation of urinary CA 19-9 levels with differential renal function and a correlation of serum CA 19-9 levels with the initial anteroposterior pelvic diameter. Receiver operator characteristic (ROC) analysis revealed a better diagnostic profile for the urinary CA 19-9 level than for the serum CA 19-9 level in terms of identifying obstruction in the hydronephrosis groups (areas under the curve = 0.8 and 0.7, respectively). The best cut-off value of for urinary CA 19-9 was 85.5 U/mL with 76% sensitivity, 85% specificity. The negative predictive value was 80%.

DISCUSSION

The results suggest that voided urine CA 19-9 levels seems to be a more useful marker than serum CA 19-9 in obstructive dilatation. An appropriate decrease in urinary CA 19-9 levels after pyeloplasty may be used as a predictor of surgical outcome. In addition, the results have a number of important diagnostic implications that should be further validated in a larger study population.

CONCLUSIONS

Based on these results, we suggest that a high urinary CA 19-9 level is a non-invasive clinically applicable marker for differentiating between obstruction and non-obstructive dilatation.

Clinical pharmacology of furosemide in neonates: a review

Furosemide is the diuretic most used in newborn infants. It blocks the Na⁺-K⁺-2Cl⁻ symporter in the thick ascending limb of the loop of Henle increasing urinary excretion of Na⁺ and Cl⁻. This article aimed to review the published data on the clinical pharmacology of furosemide in neonates to provide a critical, comprehensive, authoritative and, updated survey on the metabolism, pharmacokinetics, pharmacodynamics and side-effects of furosemide in neonates. The bibliographic search was performed using PubMed and EMBASE databases as search engines; January 2013 was the cutoff point. Furosemide half-life (t_1/2) is 6 to 20-fold longer, clearance (Cl) is 1.2 to 14-fold smaller and volume of distribution (Vd) is 1.3 to 6-fold larger than the adult values. t_1/2 shortens and Cl increases as the neonatal maturation proceeds. Continuous intravenous infusion of furosemide yields more controlled diuresis than the intermittent intravenous infusion. Furosemide may be administered by inhalation to infants with chronic lung disease to improve pulmonary mechanics. Furosemide stimulates prostaglandin E2 synthesis, a potent dilator of the patent ductus arteriosus, and the administration of furosemide to any preterm infants should be carefully weighed against the risk of precipitation of a symptomatic patent ductus arteriosus. Infants with low birthweight treated with chronic furosemide are at risk for the development of intra-renal calcifications.

Role of urinary biomarkers in the diagnosis of congenital upper urinary tract obstruction

Background:

Congenital obstructive uropathy constitutes a significant cause of morbidity in children. Currently, there is no reference standard for the diagnosis of renal obstruction in children. The noninvasive measurement of biomarkers in voided urine has considerable appeal as a potential application in children with congenital obstructive nephropathy. The aim of the present review is to explore the current role of biomarkers in the diagnosis and follow-up of obstructive uropathy in children.

Materials and Methods:

The literature database (PubMed) was searched from inception to May 2007 regarding the role of urinary biomarkers in the diagnosis and follow-up of children with congenital obstructive uropathy.

Results:

The review included 23 experimental and 33 prospective controlled clinical studies. Several cytokines, peptides, enzymes and microproteins were identified as major contributors to or ensuing from obstruction-induced renal fibrosis and apoptosis. The most important biomarkers were transforming growth factor-β₁ (TGFβ₁), epidermal growth factor (EGF), endothelin-1 (ET-1), urinary tubular enzymes [N-acetyl-β-D-glucosaminidase (NAG), γ-glutamyl transferase (GGT) and alkaline phosphatase (ALP)], and microproteins [β₂-microglobulin (β₂M), microalbumin (M. Alb) and micrototal protein (M.TP)]. All biomarkers showed different degrees of success but the most promising markers were TGFβ₁, ET-1 and a panel of tubular enzymes. These biomarkers showed sensitivity of 74.3% to 100%, specificity of 80% to 90% and overall accuracy of 81.5% to 94% in the diagnosis of congenital obstructive uropathy in children. Moreover, some of the markers were valuable in differentiation between dilated non-obstructed kidneys in need of conservative management and obstructed kidneys in need of surgical correction. Some studies demonstrated that urinary biomarkers are helpful in the evaluation of success of treatment of children with congenital renal obstruction. Some limitations of the previous studies include lack of different types of controls and small sample size. Larger studies with variable controls are invited to confirm the clinical usefulness of biomarkers in the diagnosis and follow-up of children with congenital obstructive uropathy.

Conclusion:

Urinary biomarkers are a promising tool that could be used as a noninvasive assessment of congenital renal obstruction in children.

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.

Urinary biomarkers in prenatally diagnosed unilateral hydronephrosis

The introduction of prenatal ultrasonography as a screening method entails an increasing number of infants diagnosed with prenatal hydronephrosis. Ureteropelvic junction obstruction accounts for 35% of prenatal hydronephrotic cases. Urinary tract obstruction that occurs during early kidney development affects renal morphogenesis, maturation and growth, and in the most severe cases this will ultimately cause renal insufficiency. A major challenge in the clinical management of these patients is to preserve renal function by selection of the 15%-20% who require early surgical intervention, leaving those for whom watchful waiting may be appropriate because of spontaneous resolution/stabilization without significant loss of renal function. Today, this requires medical surveillance, including repetitive invasive diuretic renograms relying on arbitrary threshold values, and therefore there is a need for non-arbitrary, non-invasive urinary biomarkers that may be used as predictors for renal structural changes and/or decreasing renal function, and thereby provide the surgeon with more clear indications for surgical intervention. In this review, we summarize the currently well-known facts about urinary biomarkers in ureteropelvic junction obstruction concerning renal function, and we also suggest potential novel urinary biomarkers.

Obstructive renal injury: from fluid mechanics to molecular cell biology

Urinary tract obstruction is a frequent cause of renal impairment. The physiopathology of obstructive nephropathy has long been viewed as a mere mechanical problem. However, recent advances in cell and systems biology have disclosed a complex physiopathology involving a high number of molecular mediators of injury that lead to cellular processes of apoptotic cell death, cell injury leading to inflammation and resultant fibrosis. Functional studies in animal models of ureteral obstruction using a variety of techniques that include genetically modified animals have disclosed an important role for the renin-angiotensin system, transforming growth factor-β1 (TGF-β1) and other mediators of inflammation in this process. In addition, high throughput techniques such as proteomics and transcriptomics have identified potential biomarkers that may guide clinical decision-making.

Biomarkers for pediatric urological disease

PURPOSE OF REVIEW

New disease-specific biomarkers are sorely needed within all fields of medicine. This review covers the current literature of biomarkers within pediatric urology and discusses future perspectives and directions for biomarker discovery.

RECENT FINDINGS

Biomarkers can be used to diagnose disease, monitor response, or sub-classify disease. Within pediatric urology, numerous markers for renal obstruction [ureteropelvic junction (UPJ)] and vesicoureteral reflux (VUR) have been identified and have shown initial promise; however, no markers have been rigorously validated or demonstrated to be clinically effective. Recent advances in proteomic technologies may provide a new discovery method to identify panels of markers for specific disease.

SUMMARY

New clinically significant biomarkers of UPJ or VUR that can improve the diagnostic capability or help determine risk for renal damage are sorely needed. However, rigorous clinical validation of previously identified markers has been limited. Other studies have demonstrated that combining various markers may help improve the ability to define clinical relevance. To improve biomarker discovery efforts, a combination of focused biomarker studies, potentially using new advanced proteomic technologies, and well designed clinical studies are needed.

Relation between radionuclide imaging and pathologic findings of ureteropelvic junction obstruction in neonatal hydronephrosis

OBJECTIVE

An excessive amount of collagen fibers around the muscle cells in the ureteropelvic junction could be responsible for obstruction in patients with hydronephrosis. We aimed to elucidate the ultrastructure of the ureters and correlate this finding with the prognostic outcome and to correlate the histopathological findings with diuretic radionuclide renography findings.

MATERIAL AND METHODS

Biopsy specimens of 20 children who underwent dismembered pyeloplasty for ureteropelvic junction obstruction were analyzed. The patients were grouped according to their age: infants (<12 months) and others (>12 months). Diuretic radionuclide imaging was performed using (99m)Tc mercaptylacetyltriglycine in the pre- and postoperative periods. Changes in differential renal function and excretion patterns on diuretic renography were evaluated in relation to the findings noted on histopathological examination of the biopsy specimens. Excretion patterns were classified as follows: A, normal; B, responsive to diuretic; C, minimal response to diuretic with some excretion after postural change; and D, very poor/no drainage despite diuretics. Biopsy materials were analyzed for the presence and extent of inflammation, fibrosis and changes in the smooth muscle layer using Masson's trichrome stain and immunohistochemical staining. Histopathological findings were graded from zero to three, depending on severity.

RESULTS

In patients aged <12 months, preoperative differential renal function (DRF) was associated with fibrosis (F) and smooth muscle hypertrophy (SMH) [mean (SD) DRF for both F and SMH were Grade 0-1, 47.8% (6.4%); Grade 2-3, 36.2% (11.3%); p<0.05]; and change in DRF was associated with inflammation [Grade 0-1, -0.1% (4.0%); Grade 2-3, 5.8% (3.0%); p<0.05]. Excretion patterns or improvement in excretion were not associated with any of the histopathological features. Change in DRF was significantly associated with inflammation Grade 2-3 (beta coefficient, 5.8; 95% CI 1.4-10.3).

CONCLUSIONS

Histopathological evaluation of renal parenchymal biopsy specimens obtained during pyeloplasty may be useful to provide an objective method for predicting the recovery of renal function. In addition, this will allow comparison of the types of histopathological alterations with the changes in differential renal function in order to predict the potential final improvement.

Increased urinary N-acetyl-beta-D-glucosaminidase activity in children with hydronephrosis

OBJECTIVE

Hydronephrosis leads to deterioration of renal function. As urinary N-acetyl-beta-D-glucosaminidase (U-NAG) activity is considered a sensitive marker of renal tubular impairment, our aim was to measure U-NAG in children with hydronephrosis and to look for a relationship among selected clinical parameters.

MATERIALS AND METHODS

We studied 31 children (22 boys and 9 girls, mean age 2.3 +/- 2.5 years) with hydronephrosis grade 1-4 that had U-NAG/creatinine ratio (U-NAG/Cr) measured.

RESULTS

The U-NAG/Cr was significantly higher in patients with hydronephrosis compared to reference data (p = 0.002). There was no difference in U-NAG/Cr between children with unilateral and bilateral hydronephrosis (p = 0.51). There was no significant difference in U-NAG/Cr between children with grades 1-3 (pooled data) and grade 4, respectively (p = 0.89). There was no correlation between U-NAG/Cr and the grade of hydronephrosis (r = 0.01).

CONCLUSIONS

U-NAG/Cr is increased in children with hydronephrosis grade 1-4, and there is no relationship with the grade of hydronephrosis. U-NAG is a useful marker of renal tubular dysfunction, however its relationship with the degree of kidney damage in patients with hydronephrosis should be considered as doubtful.

Obstructed Versus Dilated Nonobstructed Kidneys in Children With Congenital Ureteropelvic Junction Narrowing: Role of Urinary Tubular Enzymes

PURPOSE

We evaluated the role of voided urine lysosomal enzyme N-acetyl-beta-D-glucosaminidase and brush border enzymes alkaline phosphatase and gamma-glutamyl transferase in differentiating between children with ureteropelvic junction obstruction in need of pyeloplasty and those with dilated nonobstructed kidneys suitable for conservative treatment.

MATERIALS AND METHODS

The study included 35 children with unilateral ureteropelvic junction obstruction treated with pyeloplasty (study group) and 15 children with dilated nonobstructed kidneys who were treated conservatively and followed for 15 months (control group). Voided urine samples were obtained before treatment from both groups, and from the study group at 1, 2, 3, 6, 9 and 12 months postoperatively and the control group at 3, 9 and 15 months of followup. N-acetyl-beta-D-glucosaminidase, alkaline phosphatase and gamma-glutamyl transferase were measured in urine samples collected from both groups.

RESULTS

In the study group the activities of preoperative urinary N-acetyl-beta-D-glucosaminidase, alkaline phosphatase and gamma-glutamyl transferase were significantly higher than in the control group. A cutoff value of 7.8 mU/mg creatinine N-acetyl-beta-D-glucosaminidase yielded a sensitivity of 97.1%, a specificity of 80% and an overall accuracy of 92%. A cutoff value of 34.5 IU/gm creatinine alkaline phosphatase resulted in a sensitivity of 91.4%, a specificity of 100% and an overall accuracy of 94%. A cutoff value of 54 IU/gm creatinine gamma-glutamyl transferase yielded a sensitivity of 62.9%, a specificity of 100% and an overall accuracy of 74%. The combination of urinary N-acetyl-beta-D-glucosaminidase and alkaline phosphatase resulted in a sensitivity of 100%, a specificity of 80% and an overall accuracy of 94%. Compared to preoperative activities, N-acetyl-beta-D-glucosaminidase, alkaline phosphatase and gamma-glutamyl transferase decreased significantly at 12 months after pyeloplasty in the study group.

CONCLUSIONS

Voided urinary N-acetyl-beta-D-glucosaminidase, alkaline phosphatase and gamma-glutamyl transferase are accurate markers for differentiating between children with ureteropelvic junction obstruction requiring pyeloplasty and those with dilated nonobstructed kidneys suitable for conservative treatment. Measurement of these enzymes in voided urine could be used as a noninvasive tool for long-term followup of children with ureteropelvic junction obstruction after pyeloplasty and those receiving conservative treatment.

Diagnosis of Ureteropelvic Junction Obstruction in Children: Role of Endothelin-1 in Voided Urine

OBJECTIVES

To examine the role of voided urine endothelin-1 (ET-1) in the diagnosis and follow-up of children with ureteropelvic junction obstruction.

METHODS

The study included 35 children with unilateral ureteropelvic junction obstruction who underwent pyeloplasty and 30 control children, including 10 healthy children, 10 with vesicoureteral reflux, and 10 with renal stones. Voided urine samples were obtained from the children in the study group before surgery and from the renal pelvis by needle aspiration during pyeloplasty. Bladder urine samples were also collected from the study group 1, 2, 3, 6, 9, and 12 months postoperatively. Bladder urine samples were also collected from all 30 control children. ET-1 was measured in the urine samples collected from the study and control groups.

RESULTS

The preoperative ET-1 level in the voided urine of the study group was significantly greater than its level in each of the three control groups. For the whole study group, a cutoff value of 3 fmol/mg creatinine gave a sensitivity of 74.3%, a specificity of 90%, and an overall accuracy of 81.5%. In 8 children (1 year old or younger), a cutoff value of 4 fmol/mg creatinine gave a sensitivity and specificity of 100%. Compared with the preoperative value, ET-1 had decreased significantly at 12 months after pyeloplasty.

CONCLUSIONS

The ET-1 level in voided urine is a useful marker that could be used as a noninvasive tool for the diagnosis and long-term follow-up of children with ureteropelvic junction obstruction.

[Prognostic markers for congenital hydronephroses]

Watchful waiting has become the standard therapy in most cases of asymptomatic unilateral congenital hydronephroses with normal renal function. Simple, reliable, and noninvasive prognostic parameters that predict an increased risk of functional deterioration either at the initial evaluation or during follow-up would be most useful. At the moment the diameter of the renal pelvis and especially its increase is the most useful prognostic parameter, while an "obstructed" washout at furosemide isotope renography is of limited prognostic value. Preclinical and preliminary clinical studies indicate that the measurement of molecules in the urine of affected children such as TGF-31 and MCP-1 that are involved in the signal transduction during hydronephrotic atrophy might become well accepted as useful prognostic parameters in the near future.

Elevated plasma concentrations of transforming growth factor-beta 1 in patients with unilateral ureteral obstruction

We measured plasma concentrations of TGF-beta 1 in patients with obstructive ureteral calculi and compared them with the plasma concentrations of healthy volunteers. The present study was a prospective study containing a homogenous group of patients with unilateral ureteral obstruction (UUO). The study consisted of patients with ureteral stones less than 7 mm in diameter that caused mild to moderate obstruction. All patients were referred by the emergency department of our hospital and examined between April 2003 and April 2004. The presence and characteristics of both stone and obstruction were determined by plain abdominal x-ray and gray-scale ultrasonography (US). Blood samples were collected from both patients and control individuals on admission and 1 week after conservative follow-up. The plasma TGF-beta 1 concentration was determined using a quantitative sandwich enzyme immunoassay specific for TGF-beta 1. There were 35 patients with 20 women and 15 men (average age 26.8+/-5.9 years), and 15 volunteers in the control group, with nine women and six men (average age 24.2+/-4.5 years). Average stone size was 5.6 mm+/-1.2 mm (range 3.5-7) for the patient group. US showed the presence of mild hydronephrosis in 24 and moderate hydronephrosis in 11 patients. Plasma concentrations of TGF-beta 1 in patients with ureteral obstruction (1,117+/-5.8 ng/ml, range 36-2,442 ng/ml) were significantly higher than those in the healthy control group (32+/-4 ng/ml) on admission (P<0.001). There was a significant increase in TGF-beta 1 plasma concentrations in the patient group (33,525+/-6.8 ng/ml, range 1,107-73,288 ng/ml) after 1 week follow-up (P<0.001). Ureteral obstruction increases plasma TGF-beta 1 concentrations in patients with ureteral stones as in UUO models in animal studies. A concomitant treatment with an anti-fibrotic agent may reduce the incidence of renal injury during obstruction.

Voie excrétrice supérieure : physiologie, physiopathologie des obstructions et explorations fonctionnelles

The urine is transported from the renal papilla to the bladder through the upper urinary tract which allows this transport to be safe and comfortable, i.e., without any risk or pain for the kidney. This active transport depends on the smooth muscle contractile properties. The upper urinary tract is totally autonomous; this feature allows the preservation of its function after renal transplantation. However, despite its accessory role, the autonomous nervous system can modulate its activity. Upper urinary tract obstruction involves adaptative mechanisms which are different depending on the type (acute, chronic, acquired or congenital) of obstruction. Functional evaluations of the upper urinary tract are aimed at identify the urine transport conditions and the relationship between obstruction and clinical conditions such as hydronephrosis, pain or impaired renal function.

BIOMARKERS OF CONGENITAL OBSTRUCTIVE NEPHROPATHY: PAST, PRESENT AND FUTURE

PURPOSE

Congenital obstructive nephropathy constitutes one of the major causes of renal insufficiency in infants and children. This review addresses the need to define biomarkers that serve as surrogate end points for measuring the severity of obstruction, the evolution of renal maldevelopment and injury, and the response to medical or surgical intervention.

MATERIALS AND METHODS

The literature from the last 10 years was reviewed for biomarkers of congenital obstructive nephropathy. Sources of biomarkers included urine, blood, amniotic fluid, tissue and imaging techniques.

RESULTS

Previous markers of congenital obstructive nephropathy include sonographic renal pelvic diameter, quantitative diuretic renography, and markers of glomerular and tubular function. Attempts to correlate renal histological changes with differential renal function have been disappointing. Immunohistochemical analysis and laser capture microscopy should improve specificity. Most promising is the application of new insights into the cellular response of the developing kidney to urinary tract obstruction. These findings include components of the renin-angiotensin system, transforming growth factor-beta 1, monocyte chemoattractant protein-1 and epidermal growth factor. Microarray studies show unique patterns of gene expression by the neonatal rat kidney subjected to ureteral obstruction, and proteomics should provide even more sensitive biomarkers of obstructive nephropathy.

CONCLUSIONS

We must define the cellular and molecular bases of renal maldevelopment, focusing on the link between functional and developmental pathophysiology. These findings will lead to biomarkers that will optimize our management of congenital obstructive nephropathy.

Ureteropelvic Junction Obstruction: Some new Acquisitions about Etiology, Pathophysiology and Diagnostics

The etiopathogenesis of uretero-pelvic junction obstruction (UPJO) has been the subject of many speculations and it remains, in some ways, a debatable matter. Some recently reported thorough research refer to neuro-mediated pathogenetic mechanisms rather than (or together with) myogenic ones.

Advances in US, radioisotopic functional imaging, CT and RM contribute to differentiate the obstructive conditions from the non-obstructive ones and to afford today a better assessment of renal functional damage. Particularly, diuretic renography is a non-invasive test for characterization of the renal functional abnormalities resulting from UPJO. Helical CT with angiography is a useful technique for identification of crossing vessels (pyelo-vascular tangle) which can be used for the pre-surgical planning of endopyelotomy. Endoluminal ultrasonography can be used to guide the position of the incision for endopyelotomy (US-guided endopyelotomy).

Laboratory examinations are important to determine the overall renal function (serum creatinine, acid-base balance, serum electrolytes, etc.), urinary MCP-1 and NAG (markers of tubular damage), and to rule out urinary tract infections.

The management of UPJO (watchful waiting; either open or laparoscopic dismembered pyeloplasty; endoluminal procedures) is greatly influenced by the diagnostic evaluation.

The paper aims to outline the advances in both physiopathology and diagnostics of UPJO on the basis of a review of the literature.

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.

Evaluation of renal glomerular and tubular functional and structural integrity in neonates

BACKGROUND

Renal cells are not fully differentiated at birth, representing a major risk in preterm infants. We evaluated glomerular and tubular functional integrity as well as structural integrity of renal tubules among healthy full-term and preterm infants as well as diseased preterm infants.

METHODS

A total of 50 newborns (10 healthy full-term, 10 healthy preterm, and 30 diseased preterm, at 38.9 +/- 1.10, 34.2 +/- 0.92, and 32 +/- 2.47 weeks gestational age, respectively) were included in the present study. Glomerular function was assessed by measuring urinary levels of both microalbumin and immunoglobulin G as well as serum creatinine levels, whereas the proximal tubular function was investigated by measuring the urinary levels of both alpha1-microglobulin and beta2-microglobulin as well as retinol-binding protein. Also, distal tubular reabsorption capacity was investigated by assessing fractional excretion of sodium. Moreover, the structural integrity of renal proximal tubules was studied by measuring the urinary activities of both the brush-border membrane enzyme leucine-aminopeptidase (LAP) and the lysosomal enzyme N-acetyl-beta-D-glucosaminidase. The preceding investigations were done on both the first and third days of life of all 50 newborns.

RESULTS

Glomerular and tubular function and structure was relatively impaired at birth among both healthy and diseased preterm as well as healthy full-term neonates and improved rapidly thereafter. The diseased preterm neonates showed worse renal function and structure with minimal improvement regardless of the underlying sickness.

CONCLUSION

Renal insufficiency and renal immaturity could be evaluated using enzymuria and low- and high-molecular-weight proteinuria as noninvasive methods.

Partial unilateral ureteral obstruction in rats

This review comprises an overview of the current knowledge on experimental partial unilateral ureteral obstruction (PUUO) and a summary of our latest original experimental PUUO studies in rats. Neonatal PUUO is the type of obstruction that is most often encountered in pediatric clinical practice. However, the pathogenesis of PUUO is still incompletely understood. Most of our knowledge on PUUO has been derived from experimental studies in a variety of animal models. Although progress has been made, the natural history of congenital hydronephrosis is still incompletely described. The effects on kidney functions of long-term urinary tract obstruction, especially PUUO, have been less intensively studied. Recently, we created models with mild and severe PUUO in young rats by embedding the upper one fourth or the upper two thirds of the left ureter into the psoas muscle, respectively. Thereafter, the technique was used to create mild and severe PUUO in newborn rats and magnetic resonance imaging studies showed that both mild and severe obstruction caused a time-dependent decrease in renal blood flow. Compensatory increase in total kidney volume and renal vein blood flow in contralateral non-obstructed kidneys was not detectable when functional deterioration in the partially obstructed kidneys was present. Finally, we investigated the dynamic changes in renal relative signal intensity (RSI) of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) using magnetic resonance imaging in rats with partial, complete unilateral ureteral obstruction and sham-operated controls. The results showed that changes in Gd-DTPA RSI are compatible with the known physiological and anatomical changes in kidneys in response to ureteral obstruction and useful for distinguishing an obstructed from a non-obstructed collecting system and also for differentiating a partially obstructed from a completely obstructed collecting system.

Predictive value of renal histological changes for postoperative renal function improvement in children with congenital ureteropelvic junction stenosis

BACKGROUND

The aim of this study was to evaluate the relationship between renal function, as measured by diuretic radionuclide renography, and the outcome of pyeloplasty. A study was designed to evaluate renal parenchymal biopsy specimens derived from children undergoing corrective surgery for ureteropelvic junction (UPJ) stenosis, and compare these to preoperative and postoperative renal function status.

METHODS

Thirty-five children with congenital unilateral UPJ stenosis were evaluated. In addition to all conventional diagnostic procedures for UPJ stenosis, differential renal functional (DRF) activity was assessed in each of these children by obtaining 99mTc diethylenetriaminepentaacetic acid renogram curves. All children underwent dismembered pyeloplasty, and follow-up renogram evaluation was conducted 6 and 12 months after surgical repair. Biopsy specimens from renal cortical regions obtained during the surgical correction of UPJ stenosis were evaluated, and changes in renal histology were graded from I to V according to their severity. Spearman's correlation test was used to compare the histological evaluation results and the basal, 6- and 12-month follow-up DRF findings. A Wilcoxon paired test was used to evaluate statistical differences between values.

RESULTS

The findings showed a positive correlation between the severity of histological changes and DRF activity. All kidneys (22) with a DRF activity value of < 40% preoperatively demonstrated at least grade III changes when biopsy specimens were examined. Of children with a DRF activity value > 40% (13), only three showed severe histological changes. Histological grades were correlated between basal (r = -0.4; P = 0.019), 6-month (r = 0.54; P = 0.002) and 12-month (r = 0.54; P = 0.02) findings. In the Wilcoxon paired test, there was a statistically significant difference between basal and 6-month values (P < 0.05), and also between basal and 12-month values (P < 0.01). There was no statistically significant difference between 6- and 12-month values (P > 0.20).

CONCLUSION

Comparative evaluation of postoperative renal function with DRF activity and renal parenchymal histological alterations revealed a close correlation in terms of renal function improvement potential following reconstructive surgery in children with UPJ stenosis.

Recoverability of renal function after relief of acute complete ureteral obstruction: clinical prospective study of the role of renal resistive index

OBJECTIVES

To study the values of the renal resistive index (RI) before and at different points after relief of obstructive anuria and to correlate these values with the corresponding values of serum creatinine and with the recovery of renal function after release of obstruction.

METHODS

A total of 32 consecutive patients with obstructive anuria were prospectively evaluated by measurement of RI before drainage and at 3 days, 1 week, 2 weeks, and 4 weeks after drainage. Serum creatinine was measured at all points of the RI examination. Moreover, RI was measured in an age and sex-matched control group of 24 consecutive healthy donors and volunteers.

RESULTS

The study included 40 obstructed and 48 normal kidneys. In the obstructed kidneys, the mean RI values decreased significantly from 0.78 +/- 0.05 before drainage to 0.70 +/- 0.09 at 3 days after drainage (P <0.001) with an additional significant reduction to 0.68 +/- 0.08 at 7 days after drainage (P <0.01) and stabilized thereafter. Serum creatinine decreased significantly from 8.4 +/- 4.4 mg/dL before drainage to 4.7 +/- 3.8 mg/dL 3 days after drainage (P <0.001) and then to 3.6 +/- 3.7 mg/dL 7 days after drainage (P <0.001) and stabilized thereafter. The correlation between the RI and serum creatinine at the overall points of measurement was good. Obstructed kidneys were classified into two groups according to the recovery of renal function after obstruction relief: those that showed significant improvement of serum creatinine (24 kidneys, group 1) and those with no significant improvement of serum creatinine (16 kidneys, group 2). In group 1, the difference between the mean RI values before and after drainage was statistically significant (0.78 +/- 0.05 versus 0.64 +/- 0.06, P <0.001); in group 2, the difference between the before and after drainage RI values was not significant (0.781 +/- 0.040 versus 0.779 +/- 0.039). The mean RI of the normal kidneys was 0.66 +/- 0.04. A comparison between the mean RI values of the control group and the mean RI values of the obstructed patients after drainage showed no significant difference in group 1; markedly higher values were noted in group 2 at all points after drainage.

CONCLUSIONS

In the setting of acute complete renal obstruction, the RI has a good positive correlation with serum creatinine. Recovery of renal function could not be predicted from the changes in RI before obstruction release. However, a reversal of a previously elevated RI could be used as an early indicator that renal function recovery is likely.

Ureteral ischemia model: an explanation of ureteral dysfunction after chronic obstruction

BACKGROUND AND PURPOSE

Many models of smooth muscle ischemia have been developed to explain organ insufficiency or failure. Ureteral decompensation may also be described in these terms. We anticipate that ureteral ischemia will result from overdistention brought about by obstruction. A preliminary model to create an ischemic ureter is described herein.

MATERIALS AND METHODS

Six white New Zealand female rabbits were used for this study. All had their left ureters surgically ligated at the level of the urinary bladder. The right ureters served as controls. In the acute-phase group, the ureters were all reexplored 2 weeks postobstruction. Exploration of the other rabbits was delayed for 3 more weeks. A laser Doppler needle (Transonics Inc.) was used to measure tissue perfusion in the rental artery, renal vein, renal parenchyma, renal pelvis, ureteropelvic junction, upper ureter, mid ureter, lower ureter, and lateral wall of the bladder. Baseline and postobstructive measurements of tissue perfusion were collected and compared.

RESULTS

In both the acute and the chronic obstruction groups, there was a demonstrable drop-off in perfusion of the ureteral sidewall. A more notable loss of perfusion was seen in the distal ureter.

CONCLUSION

The increased wall tension in the obstructed ureter results in a significant decrease in smooth muscle perfusion. This ischemia may result in the same functional and histologic changes that occur in other smooth muscle organs. Ultimately, the poor outcomes of some restorative/reconstructive procedures on the ureter may be explained in terms of smooth muscle ischemia.

Urinary N-acetyl-beta-D-glucosaminidase concentration in patients with spinal cord injury: relationship with urodynamic parameters

OBJECTIVES

To investigate the relationships between urinary N-acetyl-beta-D-glucosaminidase (NAG) concentrations and urodynamic parameters in patients with spinal cord injury (SCI). NAG has been proposed as a marker of renal damage.

METHODS

Twenty-three patients with SCI were evaluated with urodynamic studies. Urine samples were collected from the 23 patients and 10 healthy volunteers, the NAG levels were evaluated, and the urodynamic parameters were compared with the urinary NAG levels. The patients were divided into two groups according to the amplitude of the hyperreflexic detrusor contractions (HDCs): group A, patients with an HDC amplitude of 40 cm H(2)O or greater, and group B, patients with an HDC amplitude of less than 40 cm H(2)O; group C was composed of healthy volunteers. The urinary NAG concentrations in the three groups were compared.

RESULTS

A positive correlation was found between the urinary NAG levels and the HDC amplitude and detrusor leak point pressure (P = 0.015 and 0.007, respectively). The urinary NAG concentration was 3.38 U/g in group A, 2.14 U/g in group B, and 2.12 U/g in group C. The differences in the urinary NAG concentrations between groups A and B and between groups A and C were statistically significant (P = 0.03 and P <0.001, respectively). The concentrations between groups B and C were comparable.

CONCLUSIONS

In our experience, the only urodynamic parameters that clearly and positively correlated with the urinary NAG levels were those expressing the amplitude of intravesical pressure. This result stresses the importance of reducing the intravesical pressure in patients with SCI using alternative treatments or surgical procedures if the usual conservative therapies are not effective.

Ureteral ischemia model: an explanation of ureteral dysfunction after chronic obstruction

BACKGROUND AND PURPOSE

Many models of smooth muscle ischemia have been developed to explain organ insufficiency or failure. Ureteral decompensation may also be described in these terms. We anticipate that ureteral ischemia will result from overdistention brought about by obstruction. A preliminary model of an ischemic ureter is described herein.

MATERIALS AND METHODS

Six female New Zealand rabbits were used for this study. All had their left ureters surgically ligated at the level of the urinary bladder. The right ureters served as controls. In the acute-phase group, the ureters were reexplored 2 weeks after creation of obstruction. The other three rabbits were explored 3 weeks later. A laser Doppler needle was used to measure tissue perfusion with bilateral measurements of the renal artery and vein; renal parenchyma; renal pelvis; ureteropelvic junction; upper, mid, and lower ureter; and the lateral wall of the bladder. Baseline and postobstructive measurements of tissue perfusion were collected.

RESULTS

In both the acute and chronic obstruction groups, there was a demonstrable drop-off in perfusion of the ureteral wall.

CONCLUSION

The increased wall tension in the obstructed ureter results in a significant decrease in smooth muscle perfusion. This ischemia may result in the same functional and histologic changes that occur in other smooth muscle organs deprived of normal blood flow. Ultimately, poor outcomes of some restorative/reconstructive operations on the ureter may be explainable in terms of smooth muscle ischemia.

Characteristics of protein excretion in patients with acute urinary retention

OBJECTIVE

To evaluate changes in protein leakage in the glomerular filtration barrier, and in the ability of the tubule to reabsorb proteins during and after acute urinary retention (AUR).

PATIENTS AND METHODS

Glomerular and tubular function was investigated in 24 men during AUR (mean age 68 years, mean retention time 31 h and mean retention volume 1140 mL) who were then followed for 6 months by measuring the urinary excretion of glomerular and tubular proteins, and the glomerular filtration rate (GFR). Retention was relieved by inserting a suprapubic catheter and the cause of retention treated one month later. No patient had a previous renal disease or diabetes.

RESULTS

During AUR, and after 1 and 6 months, albuminuria was detected in 100%, 92% and 54% of patients, and increased excretion of alpha1-microglobulin in 52%, 36% and 58%, of IgG in 79%, 58% and 40%, and of IgG4 in 67%, 42% and 20%, respectively. The mean GFR was normal during retention and during the follow-up.

CONCLUSION

AUR causes disturbances in both the glomerular filtration and tubular reabsorption of proteins. Albuminuria and increased excretion of IgG, IgG4 and alpha1-microglobulin occurred in most patients during AUR. After relieving retention, the albuminuria and elevated alpha1-microglobulin excretion persisted, indicating slight glomerular dysfunction and a permanent defect in the proximal tubule to reabsorb proteins. This could be caused partly by previous chronic obstruction. AUR should be relieved immediately and the basic cause treated effectively to prevent further deterioration of renal function.

Elevated bladder urine concentration of transforming growth factor-beta1 correlates with upper urinary tract obstruction in children

PURPOSE

We evaluated urinary transforming growth factor-beta1 (TGF-beta1) concentration in children with upper urinary tract obstruction as a potential tool for supporting the diagnosis of clinically significant obstruction.

MATERIALS AND METHODS

Renal pelvic and bladder urine samples were obtained for analysis from 30 patients a median of 5 months old who underwent surgery for obstruction at the ureteropelvic (29) and ureterovesical (1)junctions. Urinary TGF-beta1 concentration was measured using a quantitative sandwich enzyme-linked immunoassay technique. Bladder urine TGF-beta1 in patients with obstruction was compared with that in controls. In addition, we compared renal pelvic and bladder urine TGF-beta1 in patients with obstruction.

RESULTS

Mean bladder urine TGF-beta1 plus or minus standard error of mean was 4-fold higher in patients with upper tract obstruction than in controls (195 +/- 29 versus 47 +/- 7 pg./mg. creatinine, p <0.001). In the obstructed group mean TGF-beta1 in the renal pelvic urine was 378 +/-86 pg./mg. creatinine, or twice that of the bladder urine (p = 0.02).

CONCLUSIONS

Bladder urine TGF-beta1 in patients with upper urinary tract obstruction is significantly elevated compared with that in controls. To our knowledge our study is the first to identify a bladder urinary marker that correlates with upper urinary tract obstruction with greater than 90% sensitivity. Measuring TGF-beta1 in a voided bladder urine sample may provide an objective and noninvasive test for assisting in the diagnosis of upper urinary tract obstruction.

Elevated bladder urine concentration of transforming growth factor-beta1 correlates with upper urinary tract obstruction in children

PURPOSE

We evaluated urinary transforming growth factor-beta1 (TGF-beta1) concentration in children with upper urinary tract obstruction as a potential tool for supporting the diagnosis of clinically significant obstruction.

MATERIALS AND METHODS

Renal pelvic and bladder urine samples were obtained for analysis from 30 patients a median of 5 months old who underwent surgery for obstruction at the ureteropelvic (29) and ureterovesical (1)junctions. Urinary TGF-beta1 concentration was measured using a quantitative sandwich enzyme-linked immunoassay technique. Bladder urine TGF-beta1 in patients with obstruction was compared with that in controls. In addition, we compared renal pelvic and bladder urine TGF-beta1 in patients with obstruction.

RESULTS

Mean bladder urine TGF-beta1 plus or minus standard error of mean was 4-fold higher in patients with upper tract obstruction than in controls (195 +/- 29 versus 47 +/- 7 pg./mg. creatinine, p <0.001). In the obstructed group mean TGF-beta1 in the renal pelvic urine was 378 +/-86 pg./mg. creatinine, or twice that of the bladder urine (p = 0.02).

CONCLUSIONS

Bladder urine TGF-beta1 in patients with upper urinary tract obstruction is significantly elevated compared with that in controls. To our knowledge our study is the first to identify a bladder urinary marker that correlates with upper urinary tract obstruction with greater than 90% sensitivity. Measuring TGF-beta1 in a voided bladder urine sample may provide an objective and noninvasive test for assisting in the diagnosis of upper urinary tract obstruction.

Constant elevation in renal pelvic pressure induces an increase in urinary N-acetyl-beta-D-glucosaminidase in a nonobstructive porcine model

PURPOSE

To clarify the physiological significance of renal pelvic pressure elevations encountered in the evaluation of hydronephrotic kidney we examined the effects of different levels of renal pelvic pressure on the induction of renal injury.

MATERIALS AND METHODS

A nonobstructive porcine model was created in which the urine drained against a constant predetermined pressure gradient. Renal pelvic pressure of 10, 20 and 40 cm. was created in 2, 2 and 4 animals, respectively. During 18 to 23 hours serial urinary N-acetyl-beta-D-glucosaminidase levels were determined as an indicator of renal tubular injury. Tissue specimens were examined histologically and renal arterial blood flow was monitored.

RESULTS

Urinary N-acetyl-beta-D-glucosaminidase levels in the kidneys subjected to 10 cm. water remained essentially unchanged. However, at 20 and 40 cm. water statistically significant increases were observed. Similarly, renal arterial blood flow was unchanged at 10 cm. water but it became significantly lower than in controls at 20 and 40 cm. water. Histological evaluation revealed mild to moderate tubular dilatation in the kidneys subjected to 20 and 40 cm. water.

CONCLUSIONS

Excessively high collecting system pressure induced renal cellular injury, as reflected by an increase in urinary N-acetyl-beta-D-glucosaminidase levels. While renal pelvic pressure up to 10 cm. water appeared to be innocuous, renal cellular injury was evident within as little as 1 hour at renal pelvic pressures 20 cm. water or greater. The degree of N-acetyl-beta-D-glucosaminidase in the urine also correlated with a decrease in renal arterial blood flow.

Urine levels of transforming growth factor-beta 1 in children with ureteropelvic junction obstruction

OBJECTIVES

To determine if there are measurable quantities of transforming growth factor-beta 1 (TGF-beta 1) in the urine of children with either normal or pathologic conditions of the urinary tract, specifically vesicoureteral reflux (VUR) and ureteropelvic junction obstruction (UPJO). We also sought to determine if the urine TGF-beta level could distinguish between renal obstruction and no obstruction.

METHODS

Preoperative bladder urine from consecutive patients undergoing pyeloplasty (UPJO group; n = 13), ureteral reimplantation (VUR group; n = 11), or circumcision/orchiopexy (control group; n = 19) as well as urine from the renal pelvis of the UPJO group was collected. The urine level of TGF-beta 1 was measured using a quantitative sandwich enzyme immunoassay technique.

RESULTS

Urine level of TGF-beta 1 was detected in each group: control (26.6 +/- 6.3 pg/mL), reflux (22.1 +/- 9.6), UPJO-pelvic urine (82.4 +/- 19.3), UPJO-bladder urine (31.2 +/- 8.2). The urine TGF-beta 1 concentration in pelvic urine in the UPJO group was significantly higher than that in bladder urine in children in the UPJO group (p = 0.03). TGF-beta 1 concentrations were similar from the bladder of children in all three study groups (p = NS).

CONCLUSIONS

Urine TGF-beta 1 is detectable in children with normal and pathologic urinary tracts. The level of this urine marker is elevated in the renal pelvis of children with UPJO compared to the level in the bladder of either obstructed or nonobstructed upper urinary tracts.

Routine diagnostic imaging for childhood urinary tract infections: a systematic overview

OBJECTIVE

To assess the quality of the evidence on which current recommendations for routine diagnostic imaging for childhood urinary tract infection are based.

METHODS

A systematic overview of the literature using the MEDLINE database (1966 to October 1994), article bibliographies, and a manual search of current publications using Current Contents, was undertaken. Preset criteria were used to categorize study sample and design, and interrater reliability was assessed with a random sample.

RESULTS

A total of 434 publications were evaluated, and 63 studies met the criteria for inclusion. There was 100% interrater agreement on inclusion eligibility and design classification. No controlled trials or analytic studies evaluating routine diagnostic imaging were found. All 63 studies were descriptive, and only 10 were prospective. None of the studies provided evidence of the impact of routine imaging on the development of renal scars and clinical outcomes in children with their first urinary tract infection.

CONCLUSION

Methodologically sound, prospective studies are needed to assess whether children with their first urinary tract infection who have routine diagnostic imaging are better off than children who have imaging for specific indications. We conclude that the current recommendations are not based on firm evidence.

Urinary tract obstruction in children

PURPOSE

Perinatal identification of children with congenital urinary obstruction has challenged our understanding of the pathophysiology and clinical treatment of many children with hydronephrosis.

MATERIALS AND METHODS

A critical review of recent reports relating to congenital urinary obstruction in children was performed in an attempt to integrate clinical and experimental information.

RESULTS

Several themes emerged from the many reports relating to congenital urinary obstruction that have not been previously emphasized. Congenital obstruction begins and evolves in a developing fetal kidney, indicating the importance of the effect of obstruction on renal growth and development, which is distinct from the postnatal renal response to obstruction. Variation in the ability of the developing kidney to compensate for obstruction may be an important factor in explaining variability in clinical and experimental reports. Clinical data show an unpredictable outcome of congenital hydronephrosis. Nonoperative management of hydronephrosis is supported by empirical evidence yet raises many questions regarding the certainty of outcome and the risks involved. It imposes on the practitioner a significant clinical obligation. The ability to differentiate between clinically significant and insignificant obstruction is the current challenge to be fulfilled by integrated clinical and experimental investigation.

CONCLUSIONS

The unique features of congenital urinary obstruction separate it from better understood acquired postnatal obstruction. Understanding the effects of obstruction on the developing kidney prenatally and postnatally is critical. A definition is proposed for congenital urinary obstruction in children, that is a condition of impaired urinary drainage which, if uncorrected, will limit the ultimate functional potential of a developing kidney.

Urinary tract obstruction in children

PURPOSE

Perinatal identification of children with congenital urinary obstruction has challenged our understanding of the pathophysiology and clinical treatment of many children with hydronephrosis.

MATERIALS AND METHODS

A critical review of recent reports relating to congenital urinary obstruction in children was performed in an attempt to integrate clinical and experimental information.

RESULTS

Several themes emerged from the many reports relating to congenital urinary obstruction that have not been previously emphasized. Congenital obstruction begins and evolves in a developing fetal kidney, indicating the importance of the effect of obstruction on renal growth and development, which is distinct from the postnatal renal response to obstruction. Variation in the ability of the developing kidney to compensate for obstruction may be an important factor in explaining variability in clinical and experimental reports. Clinical data show an unpredictable outcome of congenital hydronephrosis. Nonoperative management of hydronephrosis is supported by empirical evidence yet raises many questions regarding the certainty of outcome and the risks involved. It imposes on the practitioner a significant clinical obligation. The ability to differentiate between clinically significant and insignificant obstruction is the current challenge to be fulfilled by integrated clinical and experimental investigation.

CONCLUSIONS

The unique features of congenital urinary obstruction separate it from better understood acquired postnatal obstruction. Understanding the effects of obstruction on the developing kidney prenatally and postnatally is critical. A definition is proposed for congenital urinary obstruction in children, that is a condition of impaired urinary drainage which, if uncorrected, will limit the ultimate functional potential of a developing kidney.