Antenatal Diagnosis Of Hydronephrosis Research Articles

The Role of UTD Classification in Predicting Prognosis of Antenatal Hydronephrosis

Evaluation of Patients with Antenatal Hydronephrosis According to UTD Classification
 Aim: Antenatal hydronephrosis (HN) may indicate a temporary benign condition, as well as a manifestation of congenital anomalies of the kidney and urinary system (CAKUT). Different scoring systems have been introduced to recognize CAKUT cases and to perform the necessary intervention in a timely manner. The aim of this study is to reevaluate the follow-up results of patients admitted to our hospital with antenatal HN according to the Urinary Tract Dilation (UTD) classification, and to determine the prognostic prediction of the classification in determining the presence of CAKUT and the need for surgery.
 Materials and Methods: Patients admitted to Adana City Training and Research Hospital Pediatric Nephrology and Urology outpatient clinics with the diagnosis of antenatal HN between February 2020-March 2021 included in the study. Patients were grouped according to the UTD classification. 
 Results: Of the 132 patients (93 male/39 female), 84 (64%) of the patients were evaluated as transient/physiological hydronephrosis, 48 (36%) as CAKUT. Isolated pelvic dilatation (pelvis anteroposterior diameter

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

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. 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. 34 patients with the diagnosis of antenatal hydronephrosis were evaluated prospectively. Renal pelvis diameters of all patients were above 10mm 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. 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 (259.2ng/mL) than that in the follow-up group (46.8ng/mL, p=0.028). The postoperative reduction of the median serum NGAL to 68.1ng/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. 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. Serum NGAL levels of patients with antenatal hydronephrosis may help in decision making on the surgical intervention.

Postnatal follow-up results of antenatally diagnosed hydronephrosis: A single-center experience

Aim: The incidence of antenatal hydronephrosis (AHN) has also increased with the raised use of ultrasonography (US); however, there is no consensus on how to approach the babies who were diagnosed prenatally with AHN. The present study aims to investigate the postnatal examination, treatment, and results of babies diagnosed with AHN.Material and Methods: In this study, 276 infants who were followed-up with the diagnosis of AHN between January 2012 and December 2015 in the pediatric nephrology outpatient clinic were evaluated retrospectively. Two hundred and fifty babies with AHN (196 males and 54 females) included in our study. Babies with and without abnormality were compared and etiological causes and treatment modalities of babies with AHN were investigated in the postnatal follow-up.Results: Despite no abnormality detected in 144 (57.6) AHN patients, 106 babies (42.4%) had urinary system abnormality in the postnatal US. As the underlying anomalies, ureteropelvic junction obstruction (UPJO) was the most common in 67 kidneys (63.2%); vesicoureteral reflux (VUR) was found in 29 kidneys (%27.3), ureterovesical junction obstruction (UVJO) in 5 kidneys (4.7%) and posterior urethral valve (PUV) in 3 kidneys (2.8%).Conclusion: Evaluation of babies with AHN starting from postnatal first week will provide early diagnosis of urinary system pathologies and early treatment of babies diagnosed with obstructive pathology.

One-year follow-up results of infants with antenatal hydronephrosis

Objection: Our purpose is to present the results of the one year- follow up of infants who were diagnosed with antenatal hydronephrosis. Methods: Infants (0-24 months) with diagnosis of antenatal hydronephrosis who were brought into pediatric nephrology outpatient clinics of our hospital were followed up according to the Turkish Pediatric Nephrology Society CAKUT (Congenital Anomalies of Kidney and Urinary Tract) Guidelines. Results: Ninety-three infants (64 males, 0.83 years, range 0.1-2.1 years) previously diagnosed as antenatal hydronephrosis received diagnosis of healthy infant (n=5; 5,4 %) mild (n=70; 75,3%), moderate (n=14; 15,1%), and severe (n=4; 4,3%) hydronephrosis. Voiding cystourethrogram (VCUG) was performed in 10 (10,7%) patients, 2 of them had unilateral grade 4 vesicoureteral reflux (VUR). MAG3 scan was performed in 8 (8,6%) patients, two of them had ureteropelvic junction obstruction, one of these patients had undergone pyeloplasty. After one year follow-up of 88 infants, 47 (53,4%) patients had normal, 23 (26.1%) patients had mild, 11 (12,5%) patients had moderate and 7 (8%) patients had severe hydronephrosis. Three cases (3,4%) progressed from moderate to severe disease. Conclusion: The most frequent cause of antenatal hydronephrosis among our patients was transient antenatal hydronephrosis. However follow-up of cases with a tendency to progress is important.

Evaluation and Management of Antenatal Hydronephrosis

Antenatal hydronephrosis (ANH) is one of the most common abnormal findings detected on prenatal ultrasound (US), and it has been reported in 1-5% of all pregnancies. The likelihood of significant postnatal pathologic abnormality in the urinary tract correlates with the degree of anterior-posterior diameter (APD) according to the gestational age. Detection of urologic anomalies prenatally permits fetal interventions that avoid complications in rare cases of bladder outlet obstruction with oligohydramnios even though their final benefits still remain controversial. There is no clear consensus on the extent and mode of postnatal imaging after a diagnosis of ANH. US is the mainstay of the postnatal evaluation and helps guide further testing with voiding cystourethrography (VCUG) and diuretic renography. Although most algorithms continue to recommend generous VCUG for identification of lower urinary tract anomalies, VCUG may be safely reserved for high grade ANH cases or any grade of ANH with dilated distal ureter without increasing the risk of urinary tract infection (UTI). There are conflicting studies about efficacy of postnatal prophylactic antibiotics. It still seems reasonable to consider use of a prophylactic antibiotic to prevent infant UTIs in high-risk populations, such as females and uncircumcised males with high grades of hydronephrosis, hydroureteronephrosis, or vesicouretral reflux.

Laparoscopic ipsilateral ureteroureterostomy for the management of children with duplication anomalies.

Aim:Ipsilateral ureteroureterostomy is an established method for the treatment of duplication anomalies in children. With the advent of pediatric laparoscopy, many urologic procedures in children are being performed using minimal access techniques. We present our experience with laparoscopic ipsilateral ureteroureterostomy (LIUU) for duplex anomalies.Patients and Methods:The data of children who underwent LIUU was reviewed for demographic parameters, clinical and operative details, follow-up and results.Results:Over 3 years period, LIUU was performed in eight children (age 6-60 months). Five children had complete ipsilateral duplication with ectopic upper moiety ureter, one child each had ipsilateral incomplete duplication and bilateral duplex systems (with ipsilateral ectopic upper moiety ureter). One child had ipsilateral complete duplex with Grade V vesicoureteric reflux into the lower moiety ureter. Four children had antenatal diagnosis of hydronephrosis; three children had a urinary infection and two children presented with urinary incontinence. The surgical procedure consisted of cystoscopy, retrograde studies and cannulation of the recipient ureter. Then, LIUU was performed using three ports. The ectopic (donor) ureter was divided at the pelvic brim; the recipient ureter was opened and end-to-side LIUU was performed with 5/0 vicryl stitches over a double J (DJ) stent placed in the recipient ureter. Bladder catheter was removed after 2 days, and DJ stent was removed after 4 weeks. At a mean follow-up of 19 months (3-36), all children are asymptomatic and continent, with a significant reduction in hydroureteronephrosis on ultrasound. The cosmetic results were excellent.Conclusion:LIUU is a safe and effective technique in the management of duplication anomalies in children. It could be performed with minimal blood loss, minimal postoperative pain, excellent cosmesis and good success.

Novel biomarkers of acute kidney injury: time for implementation?

Novel biomarkers of acute kidney injury: time for implementation?

PO-0780 Postnatal Follow-up Of Newborns With Prenatal Diagnosis Of Hydronephrosis

<h3>Background</h3> Prenatal Hydronephrosis is diagnosed in 1–5% of pregnancies worldwide. The diagnosis of antenatal hydronephrosis (ANH) causes stress to the parents and dilemmas to the paediatrician. <h3>Objectives</h3> To examine the correlation between the degree of the renal pelvic dilatation (RPD) detected by the first 2–5 days of life and the postnatal outcome. To investigate the correlation between bilateral hydronephrosis and the nephrologic outcome. To discuss the possibility of decreasing the postnatal examinations of these healthy babies. <h3>Methods</h3> During a period of two years, we enrolled 143 term newborns with ANH. These babies had an ultrasound at the age of 2–5 days and a second ultrasound at the age of 4–6 weeks. After the examinations they were referred to our nephrologist. <h3>Results</h3> Out of 8370 live-births, 143 infants had ANH. Six babies never completed the exam. At the first exam 69 babies were normal, 62 babies had mild, 3 babies had moderate and 3 babies had severe RPD. On their second ultrasound 76 had normal findings, 36 had mild, 8 had moderate and 12 had severe RPD. 132 babies completed both of the examinations. Bilateral hydronephrosis was detected in 33 cases during their first ultrasound while on the second only 27. There were 11 infants with UPJ obstruction 9 of them with severe RPD. We found 10 babies with VUR. Six babies needed surgical intervention. <h3>Conclusions</h3> There seems to be a correlation between the degree of RPD and the presence of postnatal pathology. Bilateral hydronephrosis probably carries increased risk for postnatal pathology.

The effect of circumcision on urinary tract infection and growth in infants without any detected postnatal urinary tract abnormalities despite antenatal diagnosis of hydronephrosis

The effect of circumcision on urinary tract infection and growth in infants without any detected postnatal urinary tract abnormalities despite antenatal diagnosis of hydronephrosis

Factors Predicting Improvement of Renal Function After Pyeloplasty in Pediatric Patients: A Prospective Study

We assessed the specific preoperative sonographic and urinary factors that may be important in predicting renal function outcomes after pyeloplasty. We prospectively studied 52 consecutive patients with ureteropelvic junction obstruction who underwent pyeloplasty at our tertiary care center between September 2009 and January 2011. Mean ± 2 SD patient age was 4.26 years (range 3 months to 18 years), and minimum followup was 6 months. Preoperative ultrasound findings recorded were pelvic anteroposterior diameter, pelvic cortical thickness, pelvic volume and pelvic cortical ratio. Spot urine protein-to-creatinine ratio from the renal pelvis and bladder was measured intraoperatively. Based on changes in differential renal function on diuretic renogram, patients were divided into 3 groups. Group 1 had stable differential renal function with less than 5% change, group 2 had improved differential renal function greater than 5% and group 3 had deterioration of differential renal function greater than 5%. Data were analyzed using SPSS®, version 17 with cross-tabulation, nonparametric tests and logistic regression. On ultrasound only anteroposterior diameter (p = 0.018) and pelvic cortical ratio (p = 0.038) were significantly different among the 3 groups. Difference in bladder sample protein-to-creatinine ratio was not significant (p = 0.69), while pelvic urine protein-to-creatinine ratio was significant (p = 0.001). Anteroposterior diameter, pelvic protein-to-creatinine ratio and pelvic cortical ratio were less than 50 mm, 0.5 and 15, respectively, in all patients with improved renal function. Sonographic and urinary biochemical parameters may predict improvement in renal function after pyeloplasty. Pelvic anteroposterior diameter, pelvic cortical ratio and pelvic urine protein-to-creatinine ratio are the most useful parameters.

Prediction of the outcome of antenatally diagnosed hydronephrosis: A multivariable analysis

PurposeThe majority of cases of antenatal hydronephrosis (ANH) resolve postnatally. The purpose of this study was to determine independent predictors for resolution of ANH using a multivariable analysis model. MethodsA retrospective study was performed on 100 children (80 males and 20 females, 118 renal units) referred to a single pediatric urology clinic with the diagnosis of ANH. Patients with ultimately resolved ANH were compared to unresolved cases in a univariate analysis in terms of sex, laterality, severity of ANH using Society for Fetal Urology (SFU) grading, antero-posterior pelvic diameter (APD), parenchymal thickness, renographic differential function and development of clinical complications, followed by a Cox proportional hazard model for multivariable analysis. ResultsMedian follow up was 34 months (range 3–204). Hydronephrosis in 62 units resolved spontaneously and pyeloplasty was done in 29. The remaining 27 units had persistent uncomplicated hydronephrosis at last follow up. Multivariate analysis showed larger APD (hazard ratio 0.54; 95%CI 0.36–0.80) and SFU grade 4 (HR 0.34; 95%CI 0.13–0.90) to be associated with a significantly lower likelihood of resolution. The mean initial APD in resolved cases was 9.4mm as opposed to 29.0mm in cases requiring surgery. ConclusionLarge initial APD has predictive value for surgical intervention. This model is helpful in counseling families about the potential outcomes of ANH.

Does Renal Function Remain Stable After Puberty in Children With Prenatal Hydronephrosis and Improved Renal Function After Pyeloplasty?

We evaluated whether improved renal function after pyeloplasty for prenatal ureteropelvic junction obstruction persisted through puberty. A total of 441 males and 137 females with a prenatal diagnosis of hydronephrosis that led to the postnatal diagnosis of ureteropelvic junction obstruction were followed at our department from 1989 to 2008. Of the patients we reviewed the records of 49 who underwent surgery between 1989 and 1992, and completed puberty. Hydronephrosis was on the right side in 18 children (36.7%) and on the left side in 31 (63.3%). According to Society for Fetal Urology classification at first presentation postnatal hydronephrosis was grades 2 to 4 in 18 (36.7%), 23 (46.9%) and 8 children (16.3%), respectively. Initially relative renal function was more than 40% in 18 children (36.7%), between 30% and 40% in 24 (49%), and less than 30% in 7 (14.3%). Preoperatively mean +/- SEM relative renal function was 36.6% +/- 7.8% in all reviewed patients. Improvement in hydronephrosis was confirmed in all patients. This remained stable during and after puberty in all except 2 patients, who required endopyelotomy 8 and 10 years following pyeloplasty, respectively, due to deterioration in hydronephrosis without a decrease in relative renal function. They showed improvement in the washout curve pattern after the procedure. Pyeloplasty led to increased relative renal function in the short term from 36.7% +/- 1.2% before surgery to 41.2% +/- 0.91% in all patients (p <0.001). It remained stable at 43.2% +/- 0.75% after puberty in all reviewed patients. To our knowledge our data show for the first time that successful pyeloplasty after the prenatal diagnosis of ureteropelvic junction obstruction is associated with improved renal function throughout puberty.

Long-term follow up of antenatally diagnosed megaureters

Aim We have retrospectively evaluated our 17 years of experience with antenatal diagnosis of hydronephrosis that led to postnatal diagnosis of megaureter, and tried to determine criteria for surgery. Patients and methods Seventy-nine children (64 boys and 15 girls) with antenatal diagnosis of hydronephrosis that led to postnatal diagnosis of megaureter were followed conservatively over a period of 18 years (1988–2006). Right ureterohydronephrosis was seen in 23 children, left in 30 and 26 had bilateral ureterohydronephrosis comprising a total of 105 renal units (RU). According to SFU (Society for Fetal Urology) classification, 8 RU were grade 1, 57 grade 2, 29 grade 3 and 11 grade 4 postnatal hydronephrosis. Mean ureteral diameter was 1.2 cm. Relative renal function was in 82 RU more than 40%, in 18 RU 30–40% and in 5 RU less than 30%. Functional deterioration of the hydronephrotic kidney of more than 5%, worsening of hydronephrosis (SFU upgrade) and a persistent obstructive curve on radionuclide scans were the main indications for surgery. Results Twenty-five (31%) children required surgical correction. Mean age at surgery was 14.3 months (range 3–60). Univariate analysis revealed that gender and side of obstruction are not significant predictive factors for surgery SFU grade 3–4 of postnatal hydronephrosis, Relative renal function less than 30% and ureteral diameter more than 1.33 cm were significant independent risk factors leading to reimplantation. Conclusions Only 30% of children with antenatal diagnosis of megaureter required surgical correction. Renal function less than 30%, grades 3 and 4 hydronephrosis, and ureteric diameter more than 1.33 cm are statistically significant and independent predictive factors for surgery.

Conservative treatment of antenatally diagnosed obstructive megaureters: long-term follow up

Purpose We retrospectively evaluated our 17 years of experience with the antenatal diagnosis of hydronephrosis, which led to a postnatal diagnosis of an obstructive megaureter and tried to determine the criteria for those who are at risk of surgery. Material and methods 79 children (64 boys and 15 girls) with an antenatal diagnosis of hydronephrosis, which led to a postnatal diagnosis of obstructive megaureter were followed for a period of 17 years (1988-2005). Rt ureterohydronephrosis was seen in 23 children, left in 30 and 26 had bilateral ureterohydronephrosis comprising 105 renal units (RU). According to the SFU classification of hydronephrosis 8 RU were with grade1, 57 with grade 2, 29 grade 3 and 11 with grade 4 postnatal hydronephrosis. Mean ureteral diameter was 1.2 cm. Relative renal function (RRF) was in 82 RU more than 40%, in 18 between 30-40% and in 5 RU less than 30%. Results 25 (31%) children required surgical correction. Mean age at surgery was 14.3 months (range 3-60 months). Univariate analysis revealed that child sex and side of obstruction are not significant predictive factors for surgery. However SFU grade 3-4 of postnatal hydronephrosis (p=0.0057 Odds ratio 0.2892), RRF less than 40% (p=0.0076, Odds ratio 0.2786) and ureteral diameter more than 1.33 cm. (p=0.0188) were significant independent risk factors leading to reimplantation. Conclusions Our data showed that only 30% of children with an antenatal diagnosis of obstructive megaureter required surgical correction. Renal function less than 40%, grade 3 and 4 hydronephrosis and ureteric diameter more than 1.33 cm are statistically significant independent predictive factors for surgery.

Micturating cystourethrograms are not necessary for all cases of antenatally diagnosed hydronephrosis

Objective Since 1995 we have, at our centre, adopted a selective approach to performing micturating cystourethrograms (MCUGs) on patients with antenatally diagnosed hydronephrosis. This study reviews the outcome of this policy. Methods We carry out MCUGs only if any of the following features are present on ultrasound: bilateral hydronephrosis, ureteric dilatation, renal scarring, bladder wall thickness greater than 5 mm, or presence of a duplex system or ureterocele. Patients with simple unilateral hydronephrosis are excluded, and are managed with 6 months’ trimethoprim prophylaxis and ultrasound surveillance with a minimum of 3 years’ follow up. Results Fifty-five patients were referred with an antenatal diagnosis of hydronephrosis between 1999 and 2002; 26 (47%) did not have an MCUG. Of these, five had increasing hydronephrosis and required surgery for pelvi-ureteric junction obstruction, and three had a multicystic dysplastic kidney on postnatal scanning. In the remaining 18 patients, the hydronephrosis resolved spontaneously, with no renal scars or asymmetry. During follow up, none of these patients had a urinary tract infection. Conclusion We believe that vesico-ureteric reflux in most antenatally diagnosed hydronephrotic kidneys is physiological rather than pathological, and resolves with time without causing long-term renal damage. This is a separate entity from, rather than a precursor of, the pathological symptomatic refluxing kidney in older, mainly female children. Taking a more conservative approach to the postnatal investigation of antenatally diagnosed hydronephrotic kidneys has not resulted in any missed damaged kidneys, but has reduced the number of invasive investigations performed. A careful protocol and detailed postnatal ultrasonography are important to prevent missed pathological cases.

Conservative Treatment of Ureteropelvic Junction Obstruction in Children with Antenatal Diagnosis of Hydronephrosis: Lessons Learned after 16 Years of Follow-Up

ObjectivesWe attempted to define predictive factors for surgery in children with antenatal diagnosis of hydronephrosis that led to postnatal diagnosis of ureteropelvic junction (UPJ) obstruction. MethodsWe retrospectively evaluated our 16-yr experience (1988–2003) with 343 children (260 male and 83 female) with antenatal diagnosis of hydronephrosis that led to postnatal diagnosis of UPJ obstruction and who were followed conservatively. Right-sided hydronephrosis was present in 110 and left-sided in 233 children. According to the Society for Fetal Urology (SFU) classification none had grade 0 of postnatal hydronephrosis, 20 had grade 1, 118 grade 2, 147 grade 3, and the remaining 58 children grade 4 postnatal hydronephrosis. Relative renal function (RRF) on radionuclide scans revealed 235 children with RRF>40%, 68 with RRF between 30% and 40%, and 40 patients with RRF<30%. Renal function deterioration >5% was the main indication for surgery. Commercially available software GraphPad Prism 4.0 (GraphPad prism, Prism 4 for Windows, version 4) using the Fisher exact test was used for statistical evaluation. ResultsSurgical correction was needed in 179 children (52.2%) during the course of conservative management. The average age at surgery was 10.6 mo (range, 1 mo to 7 yr). Of those, 50% underwent surgery during the first 2 yr of life and the majority of the remaining patients underwent surgery between the 2 and 4 yr of age; only two patients required surgery later on. Univariate analysis revealed that child sex, side of hydronephrosis, and SFU grade of prenatal hydronephrosis were not significant predictive factors for surgery. However, SFU grade 3–4 of postnatal hydronephrosis (p<0.0001; odds ratio, 0.06281) and RRF<40% (p<0.0001; odds ratio, 0.1022) were significant independent risk factors for surgery. ConclusionIn contrast with previous publications by others and by us these data show that >50% of children with antenatal diagnosis of UPJ obstruction in this series required surgical correction while on conservative protocol. SFU grade 3–4 of postnatal hydronephrosis and RRF<40% are significant independent predictive factors for surgery.

Conservative Treatment of Ureteropelvic Junction Obstruction in Children With Antenatal Diagnosis of Hydronephrosis: Lessons Learned After 16 Years of Follow-up

Conservative Treatment of Ureteropelvic Junction Obstruction in Children With Antenatal Diagnosis of Hydronephrosis: Lessons Learned After 16 Years of Follow-up

P04.40: Conservative treatment of pelvi‐ureteric junction obstruction in children with antenatal diagnosis of hydronephrosis: lessons learned after 16 years of follow up

P04.40: Conservative treatment of pelvi‐ureteric junction obstruction in children with antenatal diagnosis of hydronephrosis: lessons learned after 16 years of follow up

Antenatal hydronephrosis: Evaluation and outcome

We present a comprehensive and current review of the etiology, evaluation, treatment, and outcome of antenatal hydronephrosis. When a diagnosis of antenatal hydronephrosis is made, many questions regarding pregnancy, prenatal care, intervention, and what may be expected after birth are raised. Debate and controversy exist on the diagnosis and subsequent evaluation and management of the child with antenatal hydronephrosis. A review of the literature and our own experience with antenatal hydronephrosis are presented in order to guide the physician who is caring for mother and child.

Functional results of pyeloplasty in patients with ante‐natally diagnosed pelvi‐ureteric junction obstruction

To assess the outcome after pyeloplasty in children with an ante-natal diagnosis of hydronephrosis, shown on post-natal renography to be due to pelvi-ureteric junction (PUJ) obstruction, and in particular to review the outcome of those who had initially been managed expectantly. Between 1984 and 1995, 321 patients were diagnosed as having PUJ obstruction, after investigating ante-natal hydronephrosis. Of these, 47 had undergone pyeloplasty and also had a normal contralateral kidney; 26 patients had early pyeloplasty because of impaired function and 21 underwent surgery after a period of expectant management. Renal function was assessed renographically before and at least one year after surgery. Relative renal function was stabilized in those patients who underwent early pyeloplasty (mean differential function 28.1% before and 32.7% after surgery). In patients who underwent pyeloplasty after a period of expectant management, the mean relative function decreased from 44.8% initially to 30.5% before surgery; this recovered to 37.5% at the post-operative reassessment, representing a statistically significant loss of function (P < 0.01). In patients born with PUJ obstruction and impaired renal function, pyeloplasty failed to significantly improve function. Possibly because of cortical loss. In patients with ante-natal PUJ obstruction managed expectantly there is a small but significant risk of a modest loss of renal function.