Prenatal hydronephrosis

Matrix Metalloproteinases in Ureteropelvic Junction Obstruction: Their Role in Pathogenesis and Their Use as Clinical Markers

The obstruction of the urinary tract is responsible for obstructive nephropathy (ON), also known as uropathy, which may then evolve in a renal parenchymal disease (hydronephrosis). Regarding the etiology of ON, it has been linked to the perturbation of processes occurring during the urinary tract development such as morphogenesis, maturation, and growth. Despite the research carried out in recent years, there is still a pressing need to elucidate the molecular processes underlying the disease. This may then result in the definition of novel biomarkers that can help in patient stratification and the monitoring of therapeutic choices. Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases with key roles in extracellular matrix remodeling due to their wide cleavage specificity and ability to modulate the bioavailability of growth factors. Despite the known changes in the local tissue microenvironment at the site of the urinary tract obstruction, the role of MMPs in ureteropelvic junction obstruction (UPJO) and, therefore, in the pathogenesis of renal damage in ON is not well-documented. In this review, we underline the possible roles of MMPs both in the pathogenesis of UPJO and in the progression of related hydronephrosis. The potential use of MMPs as biomarkers detectable in bodily fluids (such as the patient's urine) is also discussed.

Urinary Tract Dilation in the Fetus and Neonate

Urinary tract dilation (UTD), previously known as hydronephrosis, is the most common congenital condition identified on prenatal ultrasonography. UTD can be physiologic and resolve spontaneously or can be caused by various congenital anomalies of the urinary tract, which can lead to renal failure if not treated properly. In 2014, a multidisciplinary consensus group established UTD definitions, a classification system, and a standardized scheme for perinatal evaluation. Various imaging modalities are available to help diagnose the cause of UTD in fetuses and neonates and to help identify those patients who may benefit from fetal or early postnatal intervention. In this article, we will review the diagnosis and quantification of antenatal and postnatal UTD based on the UTD classification system, outline the imaging studies available to both evaluateUTD and determine its cause, briefly review the most common causes of UTD in the fetus and neonate, outline management strategies for UTD including the role for fetal intervention and prophylactic antibiotics, and report on the outcome and prognosis in patients with UTD.

Association between urinary biomarkers MMP-7/TIMP-2 and reduced renal function in children with ureteropelvic junction obstruction

IMPORTANCE

Extracellular matrix proteins and enzymes involved in degradation have been found to be associated with tissue fibrosis and ureteropelvic junction obstruction (UPJO). In this study we developed a promising urinary biomarker model which can identify reduced renal function in UPJ obstruction patients. This can potentially serve as a non-invasive way to enhance surgical decision making for patients and urologists.

OBJECTIVE

We sought to develop a predictive model to identify UPJO patients at risk for reduced renal function.

DESIGN

Prospective cohort study.

SETTING

Pre-operative urine samples were collected in a prospectively enrolled UPJO biomarker registry at our institution. Urinary MMP-2, MMP-7, TIMP-2, and NGAL were measured as well as clinical characteristics including hydronephrosis grade, differential renal function, t1/2, and UPJO etiology.

PARTICIPANTS

Children who underwent pyeloplasty for UPJO.

MAIN OUTCOME MEASUREMENT

Primary outcome was reduced renal function defined as MAG3 function <40%. Multivariable logistic regression was applied to identify the independent predictive biomarkers in the original Training cohort. Model validation and generalizability were evaluated in a new UPJO Testing cohort.

RESULTS

We included 71 patients with UPJO in the original training cohort and 39 in the validation cohort. Median age was 3.3 years (70% male). By univariate analysis, reduced renal function was associated with higher MMP-2 (p = 0.064), MMP-7 (p = 0.047), NGAL (p = 0.001), and lower TIMP-2 (p = 0.033). Combining MMP-7 with TIMP-2, the multivariable logistic regression model predicted reduced renal function with good performance (AUC = 0.830; 95% CI: 0.722-0.938). The independent testing dataset validated the results with good predictive performance (AUC = 0.738).

CONCLUSIONS AND RELEVANCE

Combination of urinary MMP-7 and TIMP-2 can identify reduced renal function in UPJO patients. With the high sensitivity cutoffs, patients can be categorized into high risk (aggressive management) versus lower risk (observation).

Treatment of infants with ureteropelvic junction obstruction: findings from the PURSUIT network

PURPOSE

Studies based on administrative databases show that infant pyeloplasty is associated with minority race/ethnicity but lack clinical data that may influence treatment. Our objective was to identify clinical and demographic factors associated with pyeloplasty in infants from three large tertiary centers.

METHODS

We reviewed infants with unilateral Society for Fetal Urology (SFU) grade 3-4 hydronephrosis seen at three tertiary centers from 2/1/2018 to 9/30/2019. Patients were excluded if > 6 months old or treated surgically prior to the initial visit. Outcomes were: pyeloplasty < age 1 year and SFU grade on most recent ultrasound (US) within the first year. Covariables included: age at the initial visit, race/ethnicity, treating site, insurance type, febrile UTI, and initial imaging findings. Univariable and multivariable analyses were performed using log-rank tests and Cox proportional hazards models, respectively.

RESULTS

197 patients met study criteria; 19.3% underwent pyeloplasty. Pyeloplasty was associated with: treating site (p = 0.03), SFU 4 on initial US (p = 0.001), MAG-3 (p < 0.001), and T½ > 20 min (p < 0.001) in patients undergoing a MAG-3 (n = 107). MAG-3 (p < 0.001) and location (p = 0.08) were associated with earlier time to pyeloplasty on multivariable Cox analysis. In infants with follow-up US (n = 115), initial SFU grade, MAG-3 evaluation or findings, and pyeloplasty were not associated with improvement of hydronephrosis.

CONCLUSIONS

We found that infant pyeloplasty rates vary between sites. Prolonged T½ was associated with surgery despite prior studies suggesting this is a poor predictor of worsening dilation or function. These findings suggest the need to standardize evaluation and indications for intervention in infants with suspected UPJ obstruction.

ACR Appropriateness Criteria® Antenatal Hydronephrosis-Infant

Antenatal hydronephrosis is the most frequent urinary tract anomaly detected on prenatal ultrasonography. It occurs approximately twice as often in males as in females. Most antenatal hydronephrosis is transient with little long-term significance, and few children with antenatal hydronephrosis will have significant obstruction, develop symptoms or complications, and require surgery. Some children will be diagnosed with more serious conditions, such as posterior urethral valves. Early detection of obstructive uropathy is necessary to mitigate the potential morbidity from loss of renal function. Imaging is an integral part of screening, diagnosis, and monitoring of children with antenatal hydronephrosis. Optimal timing and appropriate use of imaging can reduce the incidence of late diagnoses and prevent renal scarring and other complications. In general, follow-up neonatal ultrasound is recommended for all cases of antenatal hydronephrosis, while further imaging, including voiding cystourethrography and nuclear scintigraphy, is recommended for moderate or severe cases, or when renal parenchymal or bladder wall abnormalities are suspected. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Learning curve or experience-related outcome: what really matters in paediatric laparoscopic pyeloplasty

Introduction

The process of improving one’s skills over time is called a “learning curve”. This term has attracted great attention during the last decades, especially in relation to laparoscopic techniques.

Aim

To assess the outcome of paediatric laparoscopic pyeloplasty (LP).

Material and methods

Retrospective analysis of the consecutive LPs. The inclusion criteria: (1) children aged < 18 years, (2) transperitoneal approach, and (3) the same operating paediatric urologist (RC). Patients with a history of any procedure on the upper urinary tract were excluded. Any surgical reintervention during follow-up was defined as a failure. The outcomes of LPs performed before 2012 (G1) were compared to those conducted between 2012 and 2016 (G2). Fisher’s exact test was used for statistical analysis.

Results

Ninety patients met the inclusion criteria, and a total of 95 LPs were performed. The mean operation time was 155 min, and the mean hospitalisation period was 2.4 days. In G1, 19 patients underwent Anderson-Hynes LP, 16 had Fenger non-dismembered LP and two underwent vascular hitch. In G2, 54, 2 and 2 patients underwent these procedures, respectively. The overall success rate was 91.5%. There were six failures in G1 and three in G2 (p = 0.147). Of the Anderson-Hynes LPs, 1/19 in G1 and 3/58 in G2 required reintervention (p = 1). For Fenger LPs, this was 4/16 and 0/2, respectively (p = 1). Only one patient required reoperation after vascular hitch.

Conclusions

The surgeons’ learning curve reflects their experience with regard to the entire therapeutic process, but not exclusively their manual skills.

Is a Reassuring MAG-3 Diuretic Renal Scan Really Reassuring?

Objective

The mercaptoacetyltriglycine-3 (MAG-3) diuretic renal scan is frequently used to diagnose obstruction in children with hydronephrosis. However, it remains unclear whether a reassuring MAG-3 diuretic scan in the presence of high-grade hydronephrosis accurately predicts the absence of obstruction. We sought to determine if a reassuring nuclear scan can accurately identify patients with high-grade hydronephrosis that can be safely observed.

Materials and Methods

We retrospectively reviewed the course of 22 children (25 renal units) ages 0-3 months with significant hydronephrosis (Society of Fetal Urology grade 3-4) detected prenatally. All patients underwent a MAG-3 diuretic nuclear renal scan.

Results

Twenty-two patients with 25 renal units were included, 19 with grade 3 and 6 with grade 4 hydronephrosis on ultrasound. Sixteen renal units had a reassuring nuclear scan (T ½ < 10 minutes, average 5.9, range 2-9). Nine renal units had indeterminate scans (T ½ 10-20 minutes, average 12.8, range 10-17). Fifteen of 16 (94%) kidneys with a reassuring nuclear scan had complete resolution of their hydronephrosis. One patient with an initially reassuring nuclear scan underwent pyeloplasty after persistent grade 4 hydronephrosis one year later prompted a repeat MAG-3 indicating obstruction. Eight of 9 (89%) patients with an indeterminate T ½ of 10-20 minutes had complete resolution of their hydronephrosis. One patient was lost to follow up. Average length of follow up and time to resolution was 23.6 months (range 4-61 months).

Conclusion

In pediatric patients with persistent antenatally detected hydronephrosis, a reassuring MAG-3 can allow for safe observation in the vast majority. Only one of 24 renal units with follow-up progressed to obstruction. All patients treated without surgery had complete resolution of their hydronephrosis. Observation with serial ultrasounds may be an appropriate alternative to operative management, even in patients with moderate to severe hydronephrosis in the presence of a reassuring or indeterminate MAG-3 diuretic scan.

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.

Epidermal growth factor and monocyte chemotactic peptide-1: potential biomarkers of urinary tract obstruction in children with hydronephrosis

OBJECTIVE

Hydronephrosis is diagnosed in 0.5% of all newborns, and ureteropelvic junction obstruction (UPJO) is a common cause. The aim of this study was to test whether specific urinary cytokines can be used as UPJO biomarkers in children with hydronephrosis.

MATERIALS AND METHODS

Twenty-eight children referred for pyeloplasty due to UPJO and 13 controls were included in this prospective study. Kidney function was assessed and urine samples collected pre-, peri-, and post-operatively. Urine levels of epidermal growth factor (EGF), monocyte chemotactic peptide-1 (MCP-1), macrophage inflammatory protein-1α (MIP-1α), interferon-γ-inducible protein-10 (IP-10), and RANTES were measured simultaneously by using a bead-based multiplex sandwich immunoassay.

RESULTS

In hydronephrotic children, preoperative urine levels were significantly increased for EGF (median 7.4 [1.2-60.2] vs. median 4.0 [1.2-13.8] ng/mg creatinine) and MCP-1 (median 136.9 [47.7-545.5] vs. median 80.1 [28.8-149.9] pg/mg creatinine) compared to those of controls. Urine levels of EGF and MCP-1 were identical to controls at the postoperative 1-year follow-up exam.

CONCLUSION

Urine levels of EGF and MCP-1 were preoperatively increased and postoperatively normalized. This study demonstrates that urine-excreted kidney cytokines may be potential biomarkers of obstruction in children with hydronephrosis.

Prenatal anteroposterior pelvic diameter cutoffs for postnatal referral for isolated pyelectasis and hydronephrosis: more is not always better

PURPOSE

Congenital hydronephrosis and isolated pyelectasis are frequently diagnosed by prenatal ultrasound. About 80% of cases resolve spontaneously in early childhood. Currently there is no agreed on protocol for prenatal followup. Most clinicians use a renal pelvis anteroposterior diameter of greater than 4 mm as a threshold for identifying isolated pyelectasis and hydronephrosis at 33 weeks of gestation or anteroposterior diameter greater than 7 mm at 40 weeks of gestation. We sought to determine a fetal renal pelvis diameter cutoff at 20 and 30 weeks of gestation that would be able to predict significant nephron uropathy requiring surgery.

MATERIALS AND METHODS

Our protocol included 2 prenatal ultrasounds at 20 and 30 weeks of gestation and 3 postnatal ultrasounds at ages 1, 6 and 12 months. Between January 2009 and December 2011 we evaluated 149 prenatal cases (130 males, 19 females) of isolated pyelectasis and 41 cases (28 males, 13 females) of hydronephrosis with a renal pelvis anteroposterior diameter of greater than 4 mm at 20 weeks of gestation.

RESULTS

For isolated pyelectasis we identified cutoffs of 6 mm at 20 weeks of gestation (100% sensitivity, 84.3% specificity) and 10 mm at 30 weeks of gestation (100% sensitivity, 91.9% specificity). For hydronephrosis we identified cutoffs of 10 mm at 20 weeks of gestation (100% sensitivity, 86.1% specificity) and 12 mm at 30 weeks of gestation (100% sensitivity, 66.7% specificity).

CONCLUSIONS

Using these thresholds, we could avoid a significant number of followup ultrasounds in the prenatal and postnatal periods, as well as invasive postnatal tests (ie voiding cystourethrography and mercaptoacetyltriglycine scintigraphy) without missing even a single case of obstructive nephropathy requiring surgery.

The Frequencies of the Urinary Anomalies which were Detected in a Foetal Autopsy Study

AIM

The detection of foetal urinary abnormalities in the antenatal period will help in an adequate post natal management and it will also have a bearing on the decision of the termination of the pregnancy. The purpose of the present study was to detect urinary anomalies in the antenatal period by doing autopsies of the aborted foetuses.

SETTINGS AND DESIGN

A cross-sectional study.

METHODS AND MATERIAL

A total of 226 aborted foetuses were autopsied. The urinary anomalies which were related to the renal parenchyma, the pelvi-ureteral system and the urinary bladder were recorded. The associated anomalies of the other organ systems were also noted. The incidences of the different urinary anomalies among the aborted foetuses were calculated. The gestational ages at which the various anomalies were detected were also studied.

RESULTS

Twenty nine of the 226 fetuses were detected to have 34 urinary anomalies. Renal agenesis was the single most common anomaly. Overall, the anomalies which were related to the renal parenchyma accounted for 67.65 % of all the urinary anomalies, while the anomalies of the pelvi-ureteral system and the bladder constituted 20.59% of the detected urinary anomalies. The anomalies of the renal parenchyma (renal agenesis and horse-shoe and polycystic kidneys) were more frequently seen in the foetuses with a shorter gestational age as compared to the gestational ages of the foetuses which showed pelvi-ureteral anomalies. The cumulative incidence of the foetuses with urinary anomalies by 30 weeks of gestation was 12.83%.

CONCLUSIONS

A significant proportion of the aborted foetuses was detected to have urinary anomalies. An early antenatal detection of these and associated anomalies has significance, as this may help in an early postnatal diagnosis and management. The degree and the extent of the detected anomalies could also help in the decision making regarding the therapeutic abortions and the future pregnancies.

Current management of antenatal hydronephrosis

The strategy for the management of children with urinary tract anomalies has changed considerably as a result of the development of ultrasound equipment and techniques that allow for detailed fetal evaluation. Hydronephrosis is the most common urogenital anomaly detected, suggesting that an obstructive process may be potentially present. The goal of postnatal management is to identify and treat those patients whose renal function is at risk, while leaving alone the high percentage of patients who are at no risk of renal damage. This management involves a spectrum of radiological, medical, and surgical interventions for diagnosis, surveillance, and treatment. In this article, we review our current understanding of the natural history of antenatal hydronephrosis and its management.

Bilateral ureteropelvic junction stenosis causing hydronephrosis and renal failure in an adult cat

A 3.5-year-old male neutered cat was presented for investigation of renomegaly appreciated during a routine physical examination. Marked renomegaly due to bilateral hydronephrosis was detected and further testing identified International Renal Interest Society stage 2, non-hypertensive, non-proteinuric chronic kidney disease. Ten months later the cat was evaluated for acute lethargy; severe azotemia with oliguria was documented. Medical therapy failed to result in clinical improvement and the cat was euthanased. Necropsy revealed bilateral marked hydronephrosis secondary to a tortuous proximal ureter consistent with proximal ureteropelvic junction stenosis. This is the first report of this disorder leading to progressive renal failure in a cat.

Hydronephrosis: a view from the inside

Unilateral ureteropelvic junction obstruction (UPJO) is the most common prenatally detected disease leading to hydronephrosis. The obstructive anatomic lesion leads to varying degrees of hydronephrosis, ranging from no apparent effect on renal function to atrophy. Furthermore, the natural course of hydronephrosis varies from spontaneous resolution to progressive deterioration and may take upwards of 3 years for a kidney to declare itself. The objectives of this article are to update our knowledge regarding the evaluation and management of UPJO in depth and to discuss the emerging value of urinary proteome analysis to the clinical arena.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Electrolyte disturbances in acute pyelonephritis

The aim of this study was to determine whether renal unresponsiveness to aldosterone associated with hyperkalemia is present in infants with acute pyelonephritis in the absence of significant urinary tract anomalies and to describe the clinical characteristics of patients presenting an inadequate renal response to hyperkalemia. The patient cohort comprised 113 infants with acute pyelonephritis (APN), based on the criteria of a temperature >38°C and significant bacteriuria. Serum and urine electrolytes, creatinine, osmolality, and renal tubular function tests were performed at diagnosis. The findings were compared to those present in 75 children who had fever without significant bacteriuria. Hyperkalemia (>5.5 mmol/L) was observed in infants with an APN diagnosis, who exhibited a lower transtubular potassium concentration gradient (TTKG) and a higher fractional sodium excretion. We defined inadequate renal response to hyperkalemia as the combination of hyperkalemia and TTKG below the normal range established for the age of the subject. Infants presenting an inadequate response to hyperkalemia were younger and associated more frequently with an APN diagnosis. This alteration could be explained by the renal interstitial inflammation present in acute pyelonephritis and the immaturity of the renal tubular responsiveness to aldosterone due to infancy in the absence of urinary tract infection or obstruction.

Probability of urinary tract infection in infants with ureteropelvic junction obstruction: is antibacterial prophylaxis really needed?

In infants with ureteropelvic junction obstruction (UPJO), the risk of urinary tract infection (UTI) is unknown, and there is a lack of prospective studies showing definitive evidence regarding the benefits and necessity of antibiotic prophylaxis. The aim of this study was to assess the risk of UTI in infants with UPJO and to determine whether the risk varies according to the degree of hydronephrosis. Infants with hydronephrosis detected prenatally or within the postnatal 28th day and who had no previous history of UTI were followed prospectively without antibacterial prophylaxis. Imaging studies were performed according to our Pediatric Uro-Nephrology Study Group protocol. Dimercaptosuccinate (DMSA) scintigraphy was performed in all infants at the end of 1 year of follow-up. Eighty-four infants (56 boys, 28 girls) were included in the study. The distribution of patients in each hydronephrosis grading group was incidentally similar. Within a median follow-up period of 18 (12-24) months, none of the patients had UTI. Furthermore, no pyelonephritic scar was found on DMSA scans in any patient. We conclude that prophylactic antibiotic usage is not indicated in infants with UPJO, regardless of the severity of hydronephrosis, as the risk of UTI is minimal in this population.

Hydronephrosis in infants and children: natural history and risk factors for persistence in children followed by a medical service

Background:

Infants with neonatal hydronephrosis and a normal voiding cystourethrogram (VCUG) are presumed to have ureteropelvic junction obstruction (UPJO). There is little current information about the natural history of children with hydronephrosis or clinical factors that predict resolution of the radiological abnormality.

Objective:

To determine the time course until spontaneous resolution of neonatal hydronephrosis and define risk factors for persistence of the abnormality.

Methods:

This retrospective single center review examined infants and children <5 years of age with hydronephrosis who were followed for at least 12 months.

Results:

136 children were identified (96 male:40 female). The mean age at diagnosis of hydronephrosis was 3.3 ± 9.7 months and 76% of the patients were diagnosed at birth. The hydronephrosis was unilateral in 98 (72%) of cases, and hydronephrosis was at least moderate in severity in 22% of affected kidneys. At last follow-up at 30 ± 10 months, the abnormality had resolved in 77 out of 115 (67%) available patients, 30 (26%) had been referred to urology, and 12 (10%) had persistent hydronephrosis. Severity of hydronephrosis was the only clinical feature that predicted persistence of the abnormality (P < 0.001). There was an association between detection at birth and lack of resolution of hydronephrosis.

Conclusions:

Children with hydronephrosis and presumed UPJO and normal kidney parenchyma can be followed for at least 2 years to allow for spontaneous resolution before referral to urology. Serial sonography can be performed at 6 month intervals in uncomplicated cases. More severe hydronephrosis and presence of the lesion at birth may predict infants and children requiring closer observation and referral for possible surgical correction of the hydronephrosis.

Localization of genetic loci controlling hydronephrosis in the Brown Norway rat and its association with hematuria

The aim of this study was to investigate the genetic basis of congenital hydronephrosis (HN), a poorly defined pathological entity, with a rat model. The Brown Norway (BN) strain spontaneously presents a high incidence of apparently asymptomatic HN, whereas the LOU strain does not. A backcross was established between these two strains [BN x (BN x LOU)] and a genomewide scan was performed with 193 microsatellite markers on 121 males and 118 females of this population, which had been phenotyped and scored for HN severity (defined as degree of renal pelvic dilation), followed by linkage analysis with Mapmaker/QTL software. Bilateral HN score was significantly linked to a locus on chromosome 6 (Z scores 4.4 and 4.8 for all rats and for females, respectively). Suggestive loci were identified on chromosomes 2 (for only right-sided HN) and 4. This is the first study in rats to identify genetic loci for HN. Three candidate genes present in these loci were sequenced and insertions detected in Id2 and Agtr1b genes in BN, which did not, however, lead to modified expression as measured by quantitative PCR. Production of a congenic line for part of the chromosome 6 locus confirmed its involvement in HN, but the phenotype was mild. Evidence of hematuria was observed in 9.6% of the backcross rats, mostly males and only in kidneys with HN, but not necessarily in the most severely affected. Hematuria also occurs in the BN colony used here, where it is due to papilloma-like lesions involving pelvic epithelial proliferation, but not in the LOU rat.

The long-term outcome of antenatal hydronephrosis up to 15 millimetres justifies a noninvasive postnatal follow-up

AIM

To assess the incidence of urinary tract infections (UTIs) and surgery in infants with different grades of antenatal hydronephrosis (ANH) and to evaluate incidence, severity and course of underlying vesicoureteral reflux (VUR).

METHODS

Retrospective data of 125 infants with ANH were collected. The patients were divided into two groups according to the anterior-posterior pelvis diameter: group I, 5-14 mm and group II, > or =15 mm.

RESULTS

UTIs developed in 4 of 106 infants from group I and 5 of 19 infants from group II. Surgical interventions were performed on 1 of 106 patients of group I and 7 of 19 patients of group II. These differences were statistically significant (p-values 0.004 and <0.001, respectively). In group I, 6 of 106 patients had VUR; none of them required surgical intervention and only two developed a UTI (one of whom also had contralateral ureteropelvic junction obstruction). Five of 19 infants in group II had underlying VUR, four of them with associated anomalies, 1 infant required surgical correction and 4 developed UTIs.

CONCLUSION

Infants with ANH up to 15 mm have a low incidence of UTIs and surgery and a low incidence and benign course of underlying VUR. Therefore, noninvasive postnatal follow-up is justified and standard voiding cystourethrography should not be performed, but only in cases of ureteric dilatation.