Postnatal Follow-Up of Newborns with Prenatal Diagnosis of Isolated HydronephrosisM
Sylvia Foldi1, Rima Krawitsky2, Renata Yakubov3, Erez Nadir1, Amit Hochberg1 and Michael Feldman1
1 Department of Neonatology, Hillel Yaffe Medical Center, Israel
2 Department of Radiology, Hillel Yaffe Medical Center, Israel
3 Department of Pediatrics, Hillel Yaffe Medical Center, Israel
Submission: February 06, 2016; Published: March 28, 2017
*Corresponding author: Sylvia Foldi, Department of Neonatology, Hillel Yaffe Medical Center, P.O. Box 169, Hadera , 38100 Israel.
How to cite this article: Foldi S, Krawitsky R, Yakubov R, Nadir E, Hochberg A, Feldman M. Postnatal Follow-Up of Newborns with Prenatal Diagnosis
of Isolated Hydronephrosis. Acad J Ped Neonatol. 2017; 4(1): 555686. DOI: 10.19080/AJPN.2017.04.555686
Objectives: To examine the correlation between the degree of renal pelvic dilatation, and the presence of bilateral dilatation detected within the first 2-5 days of life and the outcome. To consider decreasing the postnatal examinations.
Study design: Term newborns with antenatal hydronephrosis who were born in our institution between1/1/2011and 12/31/2012 were included. They underwent one ultrasound evaluation at age 2-5 days and a second one at age 4-6 weeks, after which they were referred to our nephrologist.
Results: A total of 143 were included. Of those 132 babies completed both examinations, the first ultrasound detected bilateral hydronephrosis in 33 and the second ultrasound detected bilateral hydronephrosis in 27. Eight of the 10 infants with ureteropelvic junction obstruction had severe RPD. Six needed surgical intervention.
Conclusion: An ultrasound performed within the first 2-5 days of life can be used cautiously as a predictor of the need for further investigation; it can be useful for parental counseling as well. Children with persistent mild to moderate RPD probably do not need VCUG.
Fetal hydronephrosis is a common finding on antenatal ultrasound (US) occurring in 1-5% of pregnancies worldwide. It is more frequent during the second or third trimester; rarely can be detected as early as the -12th-14th week of gestational age [1,2]. In 40-88% of the cases renal pelvic dilatation (RPD) is transient, resolving after the age of 18 months [3,4]. Urinary tract obstruction and vesicoureteral reflux (VUR) are recognized as main causes of severe RPD. Newborns with antenatal hydronephrosis (ANH) are at higher risk of VUR compared to the general population, with an incidence of 8.6% and 1% respectively . ANH requires follow-up and sometimes antibiotic prophylaxis, some of the ANH needs invasive procedures and exposes the infant to radiation and anesthesia. The postnatal follow-up is related to the cause and severity of the ANH. Unlike infants with moderate to severe RPD, those with mild RPD mostly need only clinical surveillance , in order to identify babies with significant underlying pathology.
Riccabona et al. recommended that babies with isolated ANH have at least two postnatal ultrasounds , the first more than two days postpartum, due to extracellular fluid shifts, and the second 4-6 weeks. Some of the infants with abnormal results should have a further series of US and invasive examinations such as voiding cystourethrography (VCUG) or Tcm99MAG3 renography [2,7,8]. Antibiotic prophylaxis in newborns with mild to moderate hydronephrosis is currently not recommended.
To circumvent compliance problems, we performed the initial US before discharge from hospital. In this study we aimed to determine the outcome of RPD detected by US between the 2nd -5th day of life. We also examined whether the mild RPD found in otherwise healthy babies could simply be a variant of normal anatomy and if so, whether fewer postnatal examinations are sufficient.
This study is a single-institution retrospective chart-review of
143 infants diagnosed with prenatal hydronephrosis and followed
postnatally over a 2-year period, January 1st 2011 and December
31st 2012 during which 8370 live births were treated in our
hospital. Ethical approval was obtained from the IRB. Term babies
(≥36+6 weeks) who were diagnosed by prenatal US as having
isolated ANH were included. In our population there were only
few mothers with complete antenatal documentation regarding
the degree, the laterality and the exact gestational age at the time
of the finding. We decided to omit the antenatal measurements
since most of our patients arrived without the complete data,
it was impossible to set a cut-off of antenatal RPD. Subjects
with additional congenital anomalies or genetic syndromes
were excluded. Newborns with double collecting system, single
kidney or horseshoe kidney, multicystic kidney disease were also
We defined mild hydronephrosis as RPD 4-9.9mm, moderate
hydronephrosis as RPD 10-14.9mm and severe hydronephrosis
as RPD>15mm. Several systems of grading hydronephrosis
are known . We used the system of Mami et al.  that was
consistent with the recommendations of our nephrologist.
The first US was performed when the infant was 2-5 days
of age before the discharge from hospital. All the results were
read by the same radiologist. The babies were recommended to
undergo a second US at the age of 4-6 weeks in their community
health centers, after which they returned for clinical followup
and remained under surveillance up to 18-24 months. US
results, medical interventions, treatments and diagnoses were
documented in their files (Figure 1).
Demographic data are presented in tables using the means
and standard deviations (Table 1 & 2). Nominal and ordinal data
are described by distribution tables. Student’s t-test and the
ANOVA test were used to compare means and assess significant
differences. Nominal variables were analyzed by the chi-square
test to detect differences between frequencies in case of gender.
Statistical significance was set at a P- value <0.05. All calculations
were done using IBM SPSS software version 20.
During the two year period of our study 143 (1.7%) term
neonates were diagnosed with some degree of ANH, of whom 137
completed one and 132 completed both US studies (Figure 2). In
most of the cases we had no exact data about the degree of the
ANH. Similarly the exact gestational age of the finding of the ANH
or the laterality was not well documented.
There were 105 (73%) males and 38 (27%) females. All males
underwent ritual circumcision up to the age of one month.
There was no correlation between male gender and the
severity of RPD: P=0.92 for the first US, P=0.85 for the second US
(Table 1 & 2).
Analysis of male gender and the presence of bilateral
hydronephrosis also revealed no correlation: P=0.93 for the first
US and P=0.32 for the second US (Table 3).
According to the first postnatal US 69 out of 143 (48%)
newborns had no dilatation while 62 (43%) had mild, 3 (2%)
had moderate and 3 (2%) had severe dilatation. One of the three
children with severe dilatation had bilateral RPD and all three
were referred to an early VCUG but there was no evidence of VUR.
Further investigation included a diuretic renography that detected
UPJ obstruction in all three babies. Their follow- up revealed
further dilatation of the renal pelvis. One of them had surgical
repair and the RPD of the other two stabilized and regressed by
the age of 18 months. Thirty-three (23%) infants were found to
have bilateral hydronephrosis (Table 4).
Second US was normal in 76 infants (53%). Of them 63 infants
remained with normal findings, and one was diagnosed as having
moderate RPD at the age of 4-6 weeks. Five infants from the group
with the normal examination never completed their second US,
their parents were not interested in further follow- up. At the
time of the second US, 36 newborns (25%) remained with mild
dilatation. All three babies with moderate RPD on the first US
progressed to severe dilatation. A total of 17 babies had worsening
ultrasound test (3 with previously moderate, 13 with previously
mild, and 1 baby with no RPD had further dilatation) (Figure 2). Eight newborns (5%) had moderate RPD, 12(8%) had severe
dilatation and 27 infants (19%) had bilateral ANH (Table 4).
Two (twin brothers) of the 12 babies with severe dilatation
were diagnosed with severe bilateral hydronephrosis with the
rare entity of vesicular diverticulosis in the background. Moderate
bilateral RPD had been detected on the first US without detection
of the diverticulosis; they received a 3-day course of prophylactic
antibiotic treatment around the date of circumcision. At the age
of two weeks they presented with worsening hydronephrosis.
The giant vesicular diverticulae were diagnosed by MRI. They
underwent emergency ureterostomy.
UPJ obstruction was defined by nuclear radiology of diuretic
renography. Ten babies (7%) had UPJ obstruction. Severe dilatation
had already been observed in three of them in their first US. The
RPD worsened from moderate to severe in six infants, while one
infant with mild RPD, bilateral UPJ obstruction and recurrent UTI
remained stable. One infant who had moderate bilateral RPD at his
first and severe bilateral RPD at his second US had no underlying
anatomical malformation by the end of the 18 months follow-up.
The presence of UPJ stenosis was strongly correlated to the
severity of the RPD according to both US examinations (P<0.001)
(Table 1 & 2). Of 10 infants with UPJ stenosis three (30%) had
bilateral severe RPD.
Ten babies (7%) had VUR diagnosed by VCUG and all of them
were detected with mild or moderate RPD. Their VUR improved
or resolved in all ten by the age of 18 months. Three of those
ten babies with mild RPD and VUR had bilateral persistent
hydronephrosis. One of the babies that had mild and persistent
bilateral RPD also had VUR grade V with recurrent episodes of UTI.
She needed a surgical intervention (Deflux procedure) around the
age of 6 months. Additional 15 babies had mild hydronephrosis
that was diagnosed by renal US and were not referred to VCUG.
These babies had mild but persistent RPD that resolved during the
follow-up without evidence of infection, no prophylactic antibiotic
treatment was needed.
According to these results the presence of VUR did not
correlate with the grade and severity of RPD in either the first or
the second US study (P=0.16 and P=0.15, respectively). Five of the
ten babies with VUR had bilateral RPD.
Four infants (3%) had UTI (ascertained by the review of their
medical records): one had normal results in both examinations
and, the other three had a mild bilateral RPD that resolved during
their follow-up. One of the four had VUR. There was no correlation
between the occurrence of UTI and the grade of RPD in the first
and second US examinations (P=0.89 and P=0.68, respectively)
(Table 1 & 2).
Fourteen infants (10%) underwent diuretic renography with
Tc99mMAG3. Eight (57%) had bilateral hydronephrosis and 10
(71%) had UPJ stenosis. Of 10 infants with UPJ stenosis four (40%)
had bilateral RPD and all of them had severe bilateral dilatation
Infants 1 and 12 had mild RPD in both US examinations
Infants 4, 8 and 13 had severe RPD in both US examinations
All the other infants had moderate RPD in their 1st and severe RPD in
their 2nd US examinations
Infants 10 and 14 had prophylactic AB treatment only for 3 days around
Twelve infants (8.5%) were referred to VCUG. VCUG was
recommended for boys with bilateral hydronephrosis to rule out
posterior urethral valve and for everyone after the first episode
of UTI. Seven of the 12 infants (58%) who underwent VCUG had
bilateral RPD. Ten (83%) infants of those 12 had VUR diagnosed
by VCUG. There were 15 children who were not referred to VCUG
but their VUR was diagnosed by US by visualizing the calyceal
dilatation and good corticomedullary definition during their
radiological follow-up. They did not need prophylactic antibiotics
and no further examination, their RPD and resolved by the age of
A total of 29 (20%) babies were started on antibiotic
prophylaxis during their follow-up according to their medical
records. Twenty-six had their antibiotics before diuretic
renography or before VCUG. The remaining 3 infants were started
on a short course of prophylaxis for three days around their
circumcision: their first renal US revealed a moderate bilateral
Altogether six infants (4%) had surgical intervention (two with
mild RPD and 4 with moderate to severe RPD). Three of the six had
bilateral ANH. There was also a correlation between the decision
to perform surgical repair and the severity of RPD: P=0.01 with
the first US and P<0.001 with the second US. Criteria for surgical
intervention were 1) RPD>30mm; 2) RPD>20 mm with calyceal
dilatation; 3) renal function<30%; 4) worsening renal function;
5) worsening hydronephrosis; 6) symptoms of recurrent UTI; 7)
Most infants with prenatal isolated RPD have no clinically
relevant findings and symptoms during their follow-up in infancy.
The ability to predict the postnatal course of prenatally diagnosed
hydronephrosis in a specific child is important both for the parents
and for the health care provider. Previous studies reported that
mild ANH detected before 30 weeks gestation resolves or stabilizes
during follow-up in more than 70% of cases, suggesting that mild
RPD might be a relatively benign condition .
We investigated whether the degree of RPD as measured
during the first week of life and again at the age of 4-6 weeks can
be helpful in predicting the postnatal course in terms of underlying
renal disease, testing and treatment.
The exact values of the ANH were not available to us mostly
because of lack of documentation. We decided to rely on the
first postnatal US that was performed between the 2nd and 5th
postnatal days. The decision to perform the first US before hospital
discharge was planned to circumvent problems of compliance .
The prevalence of hydronephrosis was 1.7%, similar to
the values reported in the literature . We found a male
predominance in our population of infants with ANH: male gender
had previously been described as a risk factor for postnatal
hydronephrosis [10,11]. We did not find significant difference
between male and female babies in our study population regarding
UPJ obstruction, VUR and UTI. There was no gender difference
in prophylactic antibiotic treatment or invasive procedures (i.e.
VCUG, Tc99mMAG3 and surgical intervention).
Our assessment revealed that 7% of the studied infants had
VUR, a value that is similar to the 9% described by others, 
although there are studies that describe 15%  or even as
many as 38% [12,13]. Similarly to previous reports the degree
of VUR did not appear to correlate with the degree of the RPD
. None of our study children with severe hydronephrosis had
coexisting VUR. The entity was rather detected in infants with
mild to moderate hydronephrosis. The absence of hydronephrosis,
however, does not rule out the presence of VUR . VUR had
been considered the major risk factor for UTI and renal scarring.
It was also shown however, that UTI and renal sequelae can occur
without VUR and that UTI does not always cause renal scarring.
On the other hand, the incidence of renal scarring is significantly
higher after UTI in patients with VUR . There are descriptions
that children with moderate to severe antenatal RPD were at
significant risk of UTI . In our study three of the four infants
with UTI had mild bilateral hydronephrosis, but the small numbers
do not allow to define correlation between UTI and bilateral RPD.
Several authors consider the use of neonatal US in screening for
VUR as being controversial. It probably cannot replace VCUG in
cases with high risk of VUR because it detects 25%-45% of those
patients . Several authorities recommended that postnatal
US should include not only the measurement of RPD but also
measurements of calyceal and ureteric dilatation, as well as signs
of dysplasia in order to select the infants who should undergo
VCUG [17-21]. VCUG may be unnecessary in infants with isolated
ANH who had two postnatal US examinations with a RPD <7mm,
good corticomedullary definition, mild calyceal dilatation .
The recommendations of our nephrologist were similar to
these guidelines, these infants had 2-3 additional sonographic
examinations during their follow-up without VCUG (fifteen
We detected UPJ obstruction in nearly 7% of the infants,
somewhat lower than the expected 11-12% in this population
. We could clearly demonstrate that the risk of UPJ obstruction
is higher with more extensive RPD. Most of our babies who had
severe dilatation were later diagnosed as having UPJ obstruction
(10 out of 12 infants). Furthermore four infants with UPJ stenosis
also had bilateral RPD.
The results of the renal US performed during the first 2-5 days
of life can be used for parental counseling in terms of invasive
testing, especially renography. It has to be acknowledged that the
findings that more children had a normal renal US at the age of
4-6 weeks than at 2-5 days of life goes against many prior studies
suggesting that the early renal US may be inaccurate owing to fluid
loss and fluid shifts in the neonate.
The main limitations of this study are the nature of retrospective
chart review, small numbers and the lack of the prenatal renal
measurements. We are aware of the fact that the data of the degree
and laterality of the ANH and correct prenatal documentation of
the exact gestational age of the detection would add to this study.
However we tried to examine the reliability of the first postnatal
US examination in study populations where the antenatal followup
and the patient compliance are weaker. Our study can be useful
in peripheral areas where it is difficult to perform the scheduled
ultrasound examinations during pregnancy.
Our study points to a greater risk- especially for UPJ
obstruction- in every newborn with moderate to severe
hydronephrosis confirmed during the first week of life. Bilateral
isolated RPD that is detected during the first week of life carries an
increased risk for postnatal pathology as well. It is still uncertain
whether mild isolated RPD can be considered as being a variant of
a normal anatomy. We agree that infants who have stable moderate
RPD in two consecutive US examinations will not need to undergo
VCUG. In these cases probably VUR can be diagnosed by US if
good corticomedullary definition and mild calyceal dilatation are
present with stable RPD. Based on this in our study there were 15
children with VUR who were not referred to VCUG. An ultrasound
performed during the first week of life can be used cautiously as a
predictor of the need for further investigation. It can be useful for
parental counseling as well however as a sole assessment it is not
We continue to perform the initial US examinations before
discharge in cases of antenatal diagnosis of hydronephrosis, we
are aware of the fact that the examination is more reliable after the
second postnatal day.