Prenatal hydronephrosis: early evaluation.

Abstract

Fetal hydronephrosis is the most common anomaly detected on antenatal ultrasound examination, and its significance and management remain controversial. This review aims to address the early postnatal evaluation of the child with prenatally diagnosed hydronephrosis.
The risk of significant urological pathology increases with the severity of prenatal hydronephrosis. The most common underlying conditions are ureteropelvic junction obstruction and vesicoureteral reflux. The use of postnatal ultrasonograpy in all patients with a history of any degree of prenatal hydronephrosis is routine, but ascertaining which patients require postnatal evaluation with a voiding cystourethrogram to investigate for vesicoureteral reflux remains controversial. Mild cases are the most controversial as the risk of pathology is lessened, however the risk of vesicoureteral reflux and consequent febrile urinary tract infection may be significant. Early postnatal evaluation of all children with a history of prenatal hydronephrosis with a voiding cystourethrogram may reduce this risk. No prospective randomized clinical trials are available, however, to adequately address the question of which patients require postnatal evaluation.
The postnatal management of prenatal hydronephrosis remains controversial. Sufficient data are lacking to inform patient risk stratification. Therefore, early postnatal evaluation of children with a history of any degree of prenatal hydronephrosis with an ultrasound and voiding cystourethrogram is reasonable and may reduce the risk of febrile urinary tract infection.

Full text

Page 1

Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Prenatal hydronephrosis: early evaluation
Carlos R. Estrada Jr
Introduction
Fetal hydronephrosis is the most common anomaly
detected on antenatal ultrasound examination, affecting
1–5%ofpregnancies[1].Despiteitsfrequency,theappro-
priate postnatal management of prenatal hydronephrosis
(PNH) is not well defined. Conflicting reports on the
clinical significance of PNH underpin the lack of consen-
sus on how to manage it. The degree of PNH varies from
mild to severe, and intuitively, the degree of PNH should
correlate with the severity of the underlying etiology.
While this notion has been supported [1,2??,3,4??], the
lackofcorrelationbetweendegreeofPNHandseverityof
etiologyhasalsobeenwelldocumented[5,6].Duetothese
inconsistencies,theappropriatepostnatalevaluationofthe
childwith a historyof PNHremainsincompletelydefined
and controversial [7].
Classification of prenatal hydronephrosis
The degree of PNH is inconsistently reported in the
literature, and this reflects a lack of consensus on PNH
grading. Most studies report the anterior posterior
diameter (APD) of the fetal renal pelvis at a gestational
ageorspecifictrimester.Inarecentlargemeta-analysis by
Leeetal.[1], PNH was classifiedintofivegroups basedon
APD in the second and third trimester (Table 1). This
classification system includes two additional nonconven-
tional classifications, mild/moderate and moderate/severe,
to account for reporting variability in the available litera-
ture on PNH. The use of three groups – mild, moderate,
andsevere – basedonAPDinthesecondorthirdtrimester
(Table1),however,issufficientforclinicalpractice,andis
consistent with the majority of available studies.
Clinical significance of prenatal
hydronephrosis
The risk of postnatal pathology determines the clinical
significanceofPNH,andthereforedirectspostnatalevalu-
ation and management. The most common pathological
processes include ureteropelvic junction obstruction
(UPJO) and vesicoureteral reflux (VUR), followed by
posterior urethral valves, ureteral obstruction, and other
Department of Urology, Children’s Hospital Boston and
Harvard Medical School, Boston, Massachusetts, USA
Correspondence to Carlos R. Estrada, Jr, MD,
Department of Urology, Children’s Hospital Boston,
300 Longwood Avenue, HU370, Boston, MA 02115,
USA
Tel: +1 617 355 7796; fax: +1 617 730 0474;
e-mail: carlos.estrada@childrens.harvard.edu
Current Opinion in Urology 2008, 18:401–403
Purpose of review
Fetal hydronephrosis is the most common anomaly detected on antenatal ultrasound
examination, and its significance and management remain controversial. This review
aims to address the early postnatal evaluation of the child with prenatally diagnosed
hydronephrosis.
Recent findings
The risk of significant urological pathology increases with the severity of prenatal
hydronephrosis. The most common underlying conditions are ureteropelvic junction
obstruction and vesicoureteral reflux. The use of postnatal ultrasonograpy in all patients
with a history of any degree of prenatal hydronephrosis is routine, but ascertaining
whichpatientsrequirepostnatalevaluationwithavoidingcystourethrogramtoinvestigate
for vesicoureteral reflux remains controversial. Mild cases are the most controversial
as the risk of pathology is lessened, however the risk of vesicoureteral reflux and
consequent febrile urinary tract infection may be significant. Early postnatal evaluation of
allchildrenwithahistoryofprenatalhydronephrosiswithavoidingcystourethrogrammay
reduce this risk. No prospective randomized clinical trials are available, however, to
adequately address the question of which patients require postnatal evaluation.
Summary
The postnatal management of prenatal hydronephrosis remains controversial. Sufficient
data are lacking to inform patient risk stratification. Therefore, early postnatal
evaluation of children with a history of any degree of prenatal hydronephrosis with an
ultrasound and voiding cystourethrogram is reasonable and may reduce the risk of
febrile urinary tract infection.
Keywords
early diagnosis, hydronephrosis, prenatal diagnosis, vesicoureteral reflux
Curr Opin Urol 18:401–403
? 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
0963-0643
0963-0643 ? 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins

Page 2

Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
lesscommonconditions[1,2??,4??].Theincidenceofthese
inrelationtodifferingdegreesofPNHisvariablyreported,
but the intuitive notion that more severe degrees of PNH
areassociatedwithanincreasedriskforpostnatalpathology
is well supported [1,4??]. Lee et al. demonstrated that,
overall, the risk of any postnatal pathology per degree of
PNH was 11.9% for mild, 45.1% for moderate, and 88.3%
for severe. More specifically, the risk of UPJO increased
significantly with greater degrees of PNH, but the risk of
VUR was not significantly different among all severity
groups. Other groups, however, have reported a positive
correlationbetweendegreeofPNHandincidenceofVUR;
thatis,moreseveredegreesofPNHareassociatedwithan
increasedriskofVUR[8].AvailabledatasuggestthatVUR
is present in 17–38% of children with PNH [5,8,9], but its
significance is ill defined. The questions surrounding the
associationofVURwithPNHarethebasisforalargepartof
the controversy related to the appropriate postnatal evalu-
ation of PNH. Ultimately, and underlying pathology not-
withstanding, the most important outcome measure is the
incidence of febrile urinary tract infection (UTI), but
standardized outcome reporting for PNH does not exist.
Thismakesitdifficultforthetreatingphysiciantocritically
evaluatetheavailableliterature,andvirtuallyimpossibleto
derive evidence-based practice guidelines.
In an attempt to address the critical questions regarding
clinicaloutcomeofPNH,Coelhoetal.[2??,4??]reportedin
two separate studies on the same patient cohort with a
mean APD of 10mm (range 7.8–14mm) and a median
follow up of 24months. In their reports, three important
results were provided. First, in a multivariate model two
variables were identified as independent risk factors for
UTI – femalegenderandpresenceofuropathy[2??].The
incidence of UTI was approximately 10 times greater in
girls with VUR or UPJO than in boys without these
diagnoses. The authors suggested that clinicians pay
particular attention to this subset of patients. Second,
VUR in patients with PNH is clinically significant. The
overallincidenceofVURintheir192patientswasonly8%,
but 44% of these had a UTI in the follow-up period. Only
two patients underwent ureteral reimplantation, but
further follow-up data were not provided. Other authors
havereportedthatVURassociatedwithPNHmayresolve
faster than VUR discovered following a febrile UTI
[10,11?], highlighting the variable clinical behavior of
VUR. Coelho et al. also questioned the utility of prophy-
lactic antibiotics, as 74% of their patients had their UTI
whileonprophylaxis.Alackofdataaddressingcompliance
with the prophylaxis regimen, however, precludes any
definitive conclusions. Lastly, Coelho et al. reported that
even patients with a history of mild PNH are at risk for
significant uropathy. Of the 89 patients with mild PNH,
18% had a significant uropathy (UPJO 7%, VUR 10%,
megaureter 1%). Moreover, 7.8% had a UTI during the
follow-up period, but the incidence of UTI was signifi-
cantlyhigheramonginfantswithmoderateorseverePNH
(20%). Based on these data, the authors concluded that
mild PNH may not require invasive diagnostic testing
(voiding cystourethrogram – VCUG) but rather strict
clinical surveillance for UTI and progression of hydrone-
phrosis.Whetherthesedataareoptimisticorpessimisticis
open to the readers’ interpretation, biases, and personal
experience. This author generally regards a 7.8% inci-
denceoffebrileUTIasunacceptablyhighwhencompared
with the 1% that is expected in the general population.
Postnatal evaluation
The understanding that any degree of PNH can be
associated with significant urological pathology can set
the stage for deriving a consistent approach to the evalu-
ation of the child with a history of PNH. The ultimate
goalisthepreventionoffebrileUTIanditsattendantrisk
of renal damage. As discussed above, the inconsistencies
in the available literature make it difficult to stratify
patients solely on the basis of the degree of PNH. Some
groups have utilized the degree of hydronephrosis on the
first postnatal ultrasound to direct further evaluation [12].
Other studies, however, have demonstrated a lack of
association between postnatal sonographic findings and
underlying pathology [2??,13]. Given the uncertainty of
its value and validity, it is difficult to rely solely on
ultrasonography in the postnatal evaluation of PNH. In
all cases except for severe bilateral PNH, we typically
obtain the first postnatal ultrasound in 2–4weeks post-
natally, which is consistent with most reports in the
literature. As alluded to above, the use of VCUG is
controversial. There are several papers that have recom-
mendedagainstVCUGincasesofmildormoderatePNH
based on data that may suggest that VUR in these cases
may not be clinically significant [2??,4??,5,12]. Based on
their large metaanalysis, Lee et al. [1] suggested that the
appropriate postnatal management of mild PNH remains
unclear, and that well defined prospective analysis is
required. Given the obvious inconsistencies in the litera-
ture, this author agrees with the absolute need for an
evidence-based algorithmic approach to postnatal evalu-
ation and management of PNH based on standardized
402
Paediatric urology
Table 1 Classification of prenatal hydronephrosis (PNH) by
anterior posterior diameter (APD)
PNH classification
APD (mm)
Second trimester Third trimester
Mild
Mild/moderate
Moderate
Moderate/severe
Severe
?7
<10
7–10
?7
?10
?9
<15
9–15
?9
?15
Two additional groups, mild/moderate and moderate/severe, were
included in the metaanalysis by Lee et al. [1] to account for the variability
in the literature.

Page 3

Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
outcome measures. Considering the negligible risks
associated with VCUG in the neonatal period [14] and
the significant risk of VUR and UTI associated even with
mild PNH, however, it may be prudent in the meantime
to approach all patients with any degree of PNH in a
similar fashion – early evaluation with an ultrasound and
VCUG. Another related issue is whether antibiotic pro-
phylaxis should be immediately administered to all
infants with a history of PNH. That discussion is beyond
the scope of this article, but protection against febrile
UTI while awaiting evaluation may also be considered.
Conclusion
The postnatal management of infants with a history of
PNH remains controversial. Sufficient data to inform
patient risk stratification are lacking, but recent reports
suggest that even patients with mild PNH may be at risk
for febrile UTI related to VUR. Therefore, early post-
natalevaluationofchildrenwithahistoryofanydegreeof
PNH with an ultrasound and VCUG is reasonable. Long-
term prospective studies based on standardized outcome
reporting are necessary to formulate evidence-based
clinical algorithms.
Acknowledgement
There are no potential conflicts of interest.
References and recommended reading
Papers of particular interest, published within the annual period of review, have
been highlighted as:
?
??
Additional references related to this topic can also be found in the Current
World Literature section in this issue (p. 442).
of special interest
of outstanding interest
1
LeeRS,CendronM,KinnamonDD,NguyenHT.Antenatalhydronephrosisasa
predictor of postnatal outcome: a meta-analysis. Pediatrics 2006; 118:586–
593.
2
??
Coelho GM, Bouzada MC, Lemos GS, et al. Risk factors for urinary tract
infection in children with prenatal renal pelvic dilatation. J Urol 2008; 179:
284–289.
This study is a multivariate analysis of a cohort of patients with prenatal hydro-
nephrosis that implicates female gender and urological abnormalities in the risk of
UTI.Furthermore,thedatasuggestthatevenpatientswithahistoryofmildPNHare
at significant risk for UTI.
3
Anderson NG, Allan RB, Abbott GD. Fluctuating fetal or neonatal renal pelvis:
marker of high-grade vesicoureteral reflux. Pediatr Nephrol 2004; 19:749–
753.
4
??
Coelho GM, Bouzada MC, Pereira AK, et al. Outcome of isolated antenatal
hydronephrosis: a prospective cohort study. Pediatr Nephrol 2007; 22:
1727–1734.
This study is a prospective study defining the medium term clinical outcome of a
cohort of patients with PNH. As in the related publication [2??], the data suggest
that even mild PNH may be associated with significant risk of UTI.
5
Yerkes EB, Adams MC, Pope JCt, Brock JW 3rd. Does every patient with
prenatal hydronephrosis need voiding cystourethrography? J Urol 1999;
162:1218–1220.
6
McIlroy PJ, Abbott GD, Anderson NG, et al. Outcome of primary vesicoure-
teric reflux detected following fetal renal pelvic dilatation. J Paediatr Child
Health 2000; 36:569–573.
7
Toiviainen-Salo S, Garel L, Grignon A, et al. Fetal hydronephrosis: is there
hope for consensus? Pediatr Radiol 2004; 34:519–529.
8
Brophy MM, Austin PF, Yan Y, Coplen DE. Vesicoureteral reflux and clinical
outcomes in infants with prenatally detected hydronephrosis. J Urol 2002;
168:1716–1719; discussion 1719.
9
Phan V, Traubici J, Hershenfield B, et al. Vesicoureteral reflux in infants
with isolated antenatal hydronephrosis. Pediatr Nephrol 2003; 18:1224–
1228.
10 Knudson MJ, Austin JC, McMillan ZM, et al. Predictive factors of early
spontaneous resolution in children with primary vesicoureteral reflux. J Urol
2007; 178:1684–1688.
11
?
Merlini L, Parvex P, Anooshiravani-Dumont M, et al. Postnatal management of
isolated mild pelvic dilatation detected in antenatal period. Acta Paediatr
2007; 96:1131–1134.
This study addresses patients with a history of moderate PNH. The authors show
that, overall, the incidence of VUR in this population was 10% at 1month, but only
3% at 1year.
12 Moorthy I, Joshi N, Cook JV, Warren M. Antenatal hydronephrosis: negative
predictive value of normal postnatal ultrasound: a 5-year study. Clin Radiol
2003; 58:964–970.
13 JaswonMS,DibbleL,PuriS,et al.Prospectivestudyofoutcomeinantenatally
diagnosed renal pelvis dilatation. Arch Dis Child Fetal Neonatal Ed 1999;
80:F135–138.
14 Vates TS, Shull MJ, Underberg-Davis SJ, Fleisher MH. Complications
of voiding cystourethrography in the evaluation of infants with prenatally
detected hydronephrosis. J Urol 1999; 162:1221–1223.
Prenatal hydronephrosis: early evaluation Estrada403