Is fetal hydronephrosis overdiagnosed?

Clinical Outcome of Children With Antenatally Diagnosed Hydronephrosis

Fetal renal pelvis dilation is a common condition, which is observed in 1-4. 5% of pregnancies. In many cases, this finding resolves spontaneously. However, sometimes it may be a signal of significant urinary tract pathologies. The main abnormalities found after birth are uretero-pelvic junction stenosis, primary vesicoureteral reflux, megaureter, duplex kidneys, and posterior urethral valves, with uretero-pelvic junction stenosis and primary vesicoureteral reflux accounting for most of the cases. Diagnosis, management, and prognosis at short and longer term of these conditions will be reviewed in this article.

Hydronephrosis with ureteritis developed in C57BL/6N mice carrying the congenic region derived from MRL/MpJ-type chromosome 11

Inbred MRL/MpJ mice show several unique phenotypes in tissue regeneration processes and the urogenital and immune systems. Clarifying the genetic and molecular bases of these phenotypes requires the analysis of their genetic susceptibility locus. Herein, hydronephrosis development was incidentally observed in MRL/MpJ-derived chromosome 11 (D11Mit21-212)-carrying C57BL/6N-based congenic mice, which developed bilateral or unilateral hydronephrosis in both males and females with 23.5% and 12.5% prevalence, respectively. Histopathologically, papillary malformations of the transitional epithelium in the pelvic-ureteric junction seemed to constrict the ureter luminal entrance. Characteristically, eosinophilic crystals were observed in the lumen of diseased ureters. These ureters were surrounded by infiltrating cells mainly composed of numerous CD3⁺T-cells and B220⁺B-cells. Furthermore, several Iba-1⁺macrophages, Gr-1⁺granulocytes, mast cells and chitinase 3-like 3/Ym1 (an important inflammatory lectin)-positive cells were detected. Eosinophils also accumulated to these lesions in diseased ureters. Some B6.MRL-(D11Mit21-D11Mit212) mice had duplicated ureters. We determined >100 single nucleotide variants between C57BL/6N- and MRL/MpJ-type chromosome 11 congenic regions, which were associated with nonsynonymous substitution, frameshift or stopgain of coding proteins. In conclusion, B6.MRL-(D11Mit21-D11Mit212) mice spontaneously developed hydronephrosis due to obstructive uropathy with inflammation. Thus, this mouse line would be useful for molecular pathological analysis of obstructive uropathy in experimental medicine.

Sonographic depiction of fetal ureters

AIMS

Classic literature states that the fetal ureter should not be visible unless dilated. Our main objective was to produce an effective, reproducible method for fetal ureter depiction during an anatomic survey. Our secondary objectives were to record the frequency of visible ureters among normal fetuses and among fetuses with mild pyelectasis and also to determine the diameter of the sonographically demonstrated ureter.

SUBJECTS AND METHODS

One hundred twenty consecutive fetuses undergoing a second trimester scan were enrolled in the study. Ninety-nine anatomically normal fetuses and 21 fetuses with isolated mild pyelectasis (antero-posterior renal pelvis diameter of ≥4 mm and <7 mm) were subjected to a detailed anatomical survey. One hundred twenty fetuses were analyzed bilaterally.

RESULTS

A total of 154 (64.2%) ureters were depicted. In the first group 123 (62.1%) ureters, in the second group 31 (73.8%) ureters were depicted (p = 0.06). The diameters of the ureters ranged from 0.4 to 2.7 mm. The majority (n = 80) (52%) were visualized at both proximal and distal segments.

CONCLUSIONS

Our study demonstrates that the ureter can be demonstrated in normal fetuses and in fetuses with mild pyelectasis. Ureteral depiction is likely to be composed of normal transient passage of urine associated with peristalsis and is not always a pathological finding.

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.

Antenatal hydronephrosis and the risk of pyelonephritis hospitalization during the first year of life

OBJECTIVES

To assess the risk of hospitalization for pyelonephritis within the first year of life among infants with and without antenatal hydronephrosis.

METHODS

A retrospective cohort analysis was performed using linked birth-hospital discharge records from Washington State for 1987 to 2002 to evaluate the risk of hospitalization in the first year of life for pyelonephritis among infants with and without hydronephrosis. Eligible infants had mothers who had prenatal ultrasound screening. A total of 522 singleton infants with antenatal hydronephrosis (International Classification of Diseases, Ninth Revision code 753.2) at the birth hospitalization were identified. For comparison, 2610 singletons without hydronephrosis were selected. We screened hospital discharge records for 1 year after delivery to identify hospitalizations for pyelonephritis and estimate the relative risk (RR) among infants with and without hydronephrosis.

RESULTS

Five percent of infants with antenatal hydronephrosis and 1% of those without had pyelonephritis-related hospitalizations in their first year (RR 11.8, 95% confidence interval [CI] 6.8 to 20.5). Among girls the RR was 36.3 (95% CI 10.6 to 124.0); among boys it was 5.3 (95% CI 2.2 to 13.1). In infants with hydronephrosis, girls were more likely to be hospitalized with pyelonephritis (odds ratio 2.9, 95% CI 1.2 to 6.9).

CONCLUSIONS

Infants with antenatal hydronephrosis are nearly 12 times more likely to have pyelonephritis-related hospitalizations in the first year of life. This association is stronger in girls. Parents and healthcare providers of infants with this diagnosis should be vigilant for the signs and symptoms of urinary tract infections.

Diagnostic accuracy of fetal renal pelvis anteroposterior diameter as a predictor of significant postnatal nephrouropathy: second versus third trimester of pregnancy

OBJECTIVE

The objective of the study was to determine the most effective fetal renal pelvis anteroposterior diameter thresholds and the best gestational age in predicting significant neonatal nephrouropathy and neonatal nephrouropathy requiring surgery.

STUDY DESIGN

Eighty-three newborns with prenatal ultrasound evidence of unilateral or bilateral fetal renal pelvis dilatation (anteroposterior diameter 4 mm or more) before the 26th week of gestation were systematically and prospectively investigated prenatally and postnatally.

RESULTS

Receiver operating characteristic curve analysis showed that third-trimester anteroposterior diameter cut-offs were more reliable than second-trimester cut-offs in predicting significant neonatal nephrouropathy, the best threshold being 8 mm. No significant differences were found between the 2 trimesters in the screening of fetuses at risk of neonatal nephrouropathy requiring surgery.

CONCLUSION

Significant neonatal nephrouropathy is better predicted at the third trimester, the best threshold being 8 mm, but the screening of patients at greater risk of surgery is also possible during the second trimester. An anteroposterior diameter of 11 mm or more, with an odds ratio of 128.33 (95% confidence interval 11.68 to 1408.98), is a very effective cut-off and a reliable prognostic indicator of neonatal nephrouropathy requiring surgery, even before the 26th week.

Outcome of fetal pyelectasis diagnosed antenatally

Renal pelvis dilatation is a common anomaly detected at the 20-week anomaly scan. The aim of this study was to evaluate the postnatal outcome of fetal pyelectasis in an unselected obstetric population. This was a retrospective study of fetal pyelectasis detected at midtrimester anomaly scan. Fetal pyelectasis was classified as mild if the anteroposterior renal pelvis diameter measured >5 mm-< or= 7 mm, moderate >7-< or = 10 mm and severe as >10 mm. Persistant fetal pyelectasis was defined as >7 mm in the third trimester.

RESULTS

During the study period fetal pyelectasis was identified in 74 women. 6 were excluded, as case records were not available. Mild pyelectasis was identified in 38/67(56.7%), moderate pyelectasis in 20/67(29.8%) and severe pyelectasis in 9/67(13.4%). None of the infants in the mild pyelectasis subgroup required surgery. 3/29(10%) in the moderate and severe pyelectasis subgroup required postnatal surgery. Of the 38 with mild fetal pyelectasis 13.1% had a positive postnatal diagnosis out of which 7.9% had vesico-ureteric reflux, 2.6% renal dysplasia and 2.6% pelvi-ureteric junction (PUJ) stenoses.

CONCLUSION

74% of pregnancies in the mild pyelectasis subgroup demonstrated spontaneous resolution. However persistent mild pyelectasis may lead to postnatal morbidity and should be followed up.

Mild renal pyelectasis in the second trimester: determination of cut-off levels for postnatal referral

OBJECTIVE

To establish guidelines for postnatal referral of fetuses presenting with mild pyelectasis in the second trimester of pregnancy.

METHODS

In a retrospective study, 87 fetuses with a renal pelvis anteroposterior (RPAP) diameter of > or = 4 mm and < or = 10 mm before 28 weeks of gestation were included. All patients had a third-trimester scan and fetuses with an RPAP diameter of > or = 10 mm at that stage were referred for postnatal assessment. The family practitioner of all infants with an RPAP of < 10 mm in the third trimester was contacted for follow-up information. The RPAP diameter most predictive of renal pathology was determined with receiver-operating characteristics (ROC) curve analysis for both the first and second scans.

RESULTS

In 36 of 87 infants, 49 abnormal kidneys were diagnosed. Seven infants required surgery on eight renal tracts. The ROC curves of the first scan, second scan and differences between scans resulted in an area under the curve of 0.60, 0.87 and 0.85, respectively. The sensitivities and specificities for a cut-off level of 8, 9 and 10 mm at the second scan were 80%, 71% and 61% and 79%, 90% and 93%, respectively. At a cut-off level of 10 mm, only cases of insignificant minimal dilatation and a case of vesicoureteric reflux (VUR) requiring surgery were not detected.

CONCLUSION

After establishing a diagnosis of mild pyelectasis before 28 weeks, a second scan is mandatory to determine which infants need postnatal evaluation. A cut-off level of 8 mm has a low specificity but includes most cases of pathology. A cut-off level of 10 mm detects most significant pathology; however, VUR may not be detected.

Insights into the pathogenesis and natural history of fetuses with renal pelvis dilatation

Fetal renal pelvis dilatation is a frequent abnormality that has been observed in 4.5% of pregnancies. The majority of these cases have a tendency to resolve during infancy. Nevertheless, fetal renal pelvis dilatation may be due to significant structural abnormalities such as pelvi-ureteric junction stenosis or vesico-ureteral reflux that may adversely affect renal function or cause urinary infection or sepsis. This review article aims to summarize the data regarding fetal renal pelvis dilatation and to analyze controversial attitudes in the light of the various lines of practice, and to present rational antenatal and postnatal investigation strategy.

Diagnostic accuracy of fetal renal pelvis anteroposterior diameter as a predictor of uropathy: a prospective study

OBJECTIVE

The purpose of this study was to assess the accuracy of prenatal ultrasound measurement of anteroposterior renal pelvis diameter (APD) to discriminate between significant uropathy and idiopathic renal pelvis dilatation.

METHODS

One-hundred-and-three neonates who were found to have fetal renal pelvis dilatation, defined as presence of an APD > or = 5 mm, underwent systematic investigation for uropathies and were prospectively followed. An ultrasound scan was performed after the first week of postnatal life and all infants underwent a voiding cystourethrogram. Neonates with an APD larger than 10 mm underwent renal scintigraphy. Ultrasound scans, clinical examination and laboratory reviews were scheduled at 6-month intervals. Receiver-operating characteristics (ROC) curves were constructed to determine the best cut-offs for APD to identify renal units with significant uropathy as well as those requiring surgical intervention. Significant uropathy was defined as the presence of well-established urinary tract abnormalities or when there was abnormal renal scintigraphy.

RESULTS

The estimated area under the curve for APD was 0.900 (95% CI, 0.841-0.942) indicating excellent power to discriminate between idiopathic pelvis dilatation and significant uropathy. The sensitivity and specificity for the 7.5 mm cut-off point were 97.9% and 40.6%, respectively. To identify infants who required surgical intervention, the calculated area under the curve was 0.953 (95% CI, 0.908-0.980).

CONCLUSION

Our results suggest that measurement of APD is an excellent test to identify fetuses with significant uropathy, as well as those requiring postnatal intervention.

Current management of infants with fetal renal pelvis dilation: a survey by French-speaking pediatric nephrologists and urologists

To analyze the current management recommendations among French-speaking physicians treating infants with antenatal renal pelvis dilatation, we surveyed 83 pediatric nephrologists and 68 pediatric urologists by questionnaire. A total of 45 (54%) pediatric nephrologists and 38 (56%) pediatric urologists responded. The threshold for the diagnosis of abnormal fetal renal pelvis dilatation was significantly higher among pediatric urologists than nephrologists. All responders perform renal ultrasound examinations after birth. Postnatal renal pelvis dilatation was considered abnormal if the anteroposterior diameter was >/=11+/-1.9 mm by the pediatric urologists and >/=9+/-2.9 mm by the pediatric nephrologists ( P=0.003). Pediatric urologists were more likely than nephrologists to recommend routine voiding cystourethrography [41% versus 20% ( P=0.04)]. Mercaptoacetyl-triglycine renography was the most routinely used tool to achieve functional evaluation during follow-up among the responders. Pediatric urologists were more likely to recommend surgical treatment in dilated kidneys with initial function <40%. In conclusion, pediatric urologists had significantly higher thresholds for the detection of prenatal and neonatal renal pelvis dilatation. They also more frequently recommended routine voiding cystourethrography and surgical therapy of dilated kidneys with low function than pediatric nephrologists. The variability in attitudes is most probably due to the absence of clear guidelines based on prospective and controlled trials.

A 5-year audit of 778 neonatal renal scans (Part 2). Miscellaneous anomalies in 59 infants: A pictorial presentation

In this 5-year review of 778 neonatal renal scans seen in an obstetric hospital, Mercy Hospital for Women, Melbourne, most infants were referred because of antenatal ultrasound findings. Ninety-two percent of these had fetal pyelectasis. The results were classified on the ultrasound findings. The majority of neonates (76%) had a normal postnatal scan. A number had vesicoureteric reflux found on micturating cystourethrogram. Persisting mild/moderate pyelectasis or hydronephrosis (15%) proved to be a normal variant in many infants, but had a similar appearance to those with an early obstructive cause (1%). There were 59 infants (8%) with a miscellaneous group of renal anomalies, many with a characteristic antenatal ultrasound appearance suggesting the diagnosis. Review of these 59 infants illustrates the anomalies seen and reports the associated investigations and subsequent outcome in most cases.

A 5-year audit of 778 neonatal renal scans (Part 1): Perplexing pyelectasis and suggested protocol for investigation

In this 5-year review of 778 neonatal renal scans seen in an Obstetric Hospital, most infants were referred because of antenatal ultrasound findings, 92% with fetal pyelectasis. The results were classified according to the ultrasound findings. The majority of neonates (76%) had a normal postnatal scan. A number had vesicoureteric reflux (VUR) found on a micturating cystourethrogram. Persistant mild to moderate pyelectasis or hydronephrosis (15%) proved to be a normal variant in many infants, but had a similar appearance to those with an early obstructive cause (1%). Pyelectasis has proved to be a poor predictor of VUR. A protocol outlining paediatric management for neonates with persisting pyelectasis is included. There were 59 infants (8%) with a miscellaneous group of renal anomalies, many with a characteristic antenatal ultrasound appearance suggesting the diagnosis. These infants have been separately reported and illustrated (Part 2). Overall, 13% of infants were found to have significant findings of obstruction, VUR or miscellaneous anomalies affecting management.

Antenatal Hydronephrosis: Negative Predictive Value of Normal Postnatal Ultrasound—a 5-year Study

AIM

To determine whether normal postnatal ultrasound, as part of a strict screening protocol for the detection and follow-up of antenatal hydronephrosis, effectively excludes the majority of babies with congenital urinary tract abnormalities that would otherwise present with a urinary tract infection.

MATERIALS AND METHODS

We retrospectively reviewed all babies who had postnatal follow-up of antenatally detected hydronephrosis over a 5-year period at our institution, a district general Trust with a specialist paediatric unit. We then studied all babies presenting with urinary tract infection before their first birthday to our institution over the same period. By cross-referencing these two study groups we were able to determine which babies developed a urinary tract infection having been previously discharged after normal postnatal ultrasound.

RESULTS

Four hundred and twenty-five babies had postnatal follow-up of antenatal hydronephrosis. Of these, 284 were investigated with ultrasound alone. In the same 5-year period, 230 babies presented with urinary tract infection before their first birthday. Only three of these babies had been previously discharged after normal postnatal ultrasound. The negative predictive value of a normal postnatal ultrasound was therefore 98.9% (281/284) for babies who subsequently presented with a urinary tract infection before their first birthday.

CONCLUSION

Careful antenatal and postnatal ultrasound with strict protocols is effective in detecting congenital renal tract abnormalities. Infants discharged after normal postnatal ultrasound are highly unlikely to still have an undetected urinary tract abnormality. We suggest that all babies with antenatal hydronephrosis are started on prophylactic antibiotics at birth, pending further investigation. All babies without features of severe obstruction antenatally should have their postnatal ultrasound delayed for a month. We recommend selective use of micturating cystourethrogram (MCUG), and delaying this investigation until the baby is 3 to 4 months old to allow for spontaneous resolution of vesicoureteric reflux. We do not believe that all babies with antenatal hydronephrosis require MCUG, providing a clear protocol is followed.

Results of systematic screening for minor degrees of fetal renal pelvis dilatation in an unselected population

OBJECTIVE

The purpose of this study was to determine the incidence of minor degrees of renal pelvis dilatation that is detected by antenatal ultrasound scanning in an unselected population and its value in the prediction of significant uropathies.

STUDY DESIGN

This prospective study was conducted over a 24-month period. Infants with an anteroposterior pelvic diameter of >or=4 mm in the second trimester and/or >or=7 mm but <15 mm in the third trimester were enrolled.

RESULTS

Pyelectasis was found in 4.5% of 5643 fetuses (1.5% with significant uropathy). Among the 213 infants whose cases were followed, 132 infants (62%) had renal anomalies, but only 83 infants (39%) had significant uropathies. The ability of the third-trimester renal pelvis dilatation to predict renal abnormalities showed a positive predictive value of 69%. Pyelectasis that was detected only in the second trimester revealed a significant uropathy in 12% of the infants.

CONCLUSION

Pyelectasis was found in 4.5% of fetuses. The third-trimester anteroposterior renal pelvis diameter of >or=7 mm was the best ultrasound criterion to predict postnatal uropathies.

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.