Canadian Urological Association/Pediatric Urologists of Canada guidelines on the investigation and management of antenatally detected hydronephrosis. (2025)

Introduction

Prior to the advent of maternal ultrasonography in the 1980s,children with significant congenital hydronephrosis requiring surgerypresented symptomatically with abdominal pain, urinary infection,hypertension, hematuria, or failure to thrive. Antenatal hydronephrosis(ANH) became one of the most commonly detected ultrasound findings,affecting 1-5% of pregnancies. (1) The majority of ANH in the thirdtrimester is discovered due to ultrasound for maternal indications. Thebenefits of this early detection of urinary tract dilation include areduction in the renal damage due to obstruction and infection. (2,3) Onthe other hand, many of these antenatally detected cases spontaneouslyresolve with observation and consequently can be submitted tounnecessary investigations and continued medical followup. (4) Thechallenge to this day remains to predict which of these prenatallydetected infants will require corrective surgery, prior to thedevelopment of symptoms or potentially irreversible renal damage, thuspermitting a more tailored screening.

Methodology

This article presents an update to the 2009 guidelines(5), based onreview of the current literature. The available evidence is summarizedand recommendations provided based on the modified Oxford Center forEvidence-Based Medicine grading system for guideline recommendations, asemployed by the International Consultation on Urologic Disease (6).

Characterizing the patient population

The literature on ANH suffers from a lack of good qualityprospective studies, which precludes any recommendations with a highlevel of evidence. Published prospective studies are hindered by thelimitation that to this date no single gold standard diagnostic test forurinary obstruction exists. In order to appreciate this dilemma, it isimperative to understand the difference between hydronephrosis andurinary tract obstruction. Hydronephrosis simply refers to dilation ofthe renal collecting system. Congenital renal obstruction has beendefined as "impaired urinary drainage which, if uncorrected, willlimit the ultimate functional potential of the developing kidney"(7). To date, no single imaging study exists which can prove thepresence of renal obstruction, contributing to the controversysurrounding management.

The differential diagnosis of ANH, in order of likelihood, includestransient primary hydronephrosis, uretero-pelvic junction obstruction(UPJO), vesicoureteric reflux (VUR), uretero-vesical junctionobstruction (UVJO) or primary non-obstructive megaureter, ureterocele,ectopic ureter and causes of megacystis. Megacystis, or dilated urinarybladder, includes causes of bladder outlet obstruction due to posteriorurethral valves (PUV) and less commonly Prune Belly syndrome,Megacystis-Megaureter syndrome, megacystis-microcolon intestinalhypoperistalsis syndrome (MMIHS), anterior urethral valves,megalourethra, urethral atresia and cloacal anomalies. Some of theseentities have gender specific and hereditary predispositions, which havepotential diagnostic implications not discussed herein.

Various grading systems for the severity of ANH exist, which areparamount in decision making. The simplest grading is theantero-posterior renal pelvic diameter (APD), which is an objectivemeasure of the degree of pyelectasis or dilation of the renal pelvis inthe transverse plane. Descriptors such as mild, moderate or severeshould not be used in isolation as they are subjective and undefined.Since 1993 the standard amongst pediatric urologists in North Americahas been the classification from the Society for Fetal Urology (SFU),Table 1(8). The SFU grading classification has been validated with goodintra-rater reliability and modest inter-rater reliability, with grade 3being the least reliable(9). The SFU has recently proposed the UTDclassification, which combines elements of both APD and SFU. Initialvalidation has been possibly more reliable than the SFU system (10, 11)with others showing the same issues with inter-rater reliability (12).The UTD classification for HN was released to address potentialshortcomings of the current SFU grading system; more specifically todeal with inconsistencies between prenatally detected HN and postnatalmanagement strategies within and across specialties. The UTDclassification uses a 3-point system based on six different ultrasoundobservations [renal pelvis anterior-posterior diameter (APD), calycealdilation, parenchymal thickness/appearance, ureteral dilation, andbladder abnormalities] to stratify patients into 3 risk categories basedon the most concerning of 6 ultrasound variables (UTD P1, P2, and P3).UTD P1 (low risk) with 10-15mm renal pelvis APD and central calycealdilation to UTD P3 with renal pelvis APD >15mm, peripheral calycealdilation, parenchymal thinning, ureter dilation, and or bladderabnormality (high risk)(13). Nevertheless, the added complexity of theUTD classification imposes a need for greater validation prior tosupplanting the simplicity of the SFU classification.

Definition of the dilated urinary tract

The diagnosis and management of the fetus or child with a dilatedurinary tract requires an understanding of what are acceptable degreesof dilation, Table 2(1). The definitions of pyelectasis, hydroureter andmegacystis will determine the intensity of investigations and frequencyof follow-up, both antenatally and postnatally. It is generally acceptedthat pyelectasis in the third trimester is defined as APD greater than4-5 mm (1). Nevertheless, the ideal cut-off for routine postnatalscreening remains controversial, since high grades of ANH can resolvepostnatally and conversely low grades can deteriorate. Notwithstanding,most centres use a cutoff of 7mm in the third trimester for indicating apostnatal evaluation. Postnatal data on MRI, not ultrasound, suggestthat the normal APD in children is 3 mm at 1 year of age, 6 mm at 18years with the 99th percentile for children <5 years of age being<10 mm(1).

Aside from APD, the severity of hydroureteronephrosis (HUN) hasalso been classified by the SFU based on the transverse measure of thedistal ureter; Grade 1 is < 7mm, Grade 2 is 7 to 10mm and Grade 3 is> 10 mm (8). This classification is mostly descriptive and has notbeen submitted to much scrutiny. The dilated fetal bladder or megacystishas been defined based on the formula for fetal bladder sagittal length(FBSL) in mm = gestational age in weeks plus 2 (15)

It is important to remember that a dilated urinary tract does notautomatically infer obstruction of the urinary tract. Whereashydronephrosis equates to a dilated renal collecting system, obstructioncannot be proven on the basis of any single imaging study, hence thenecessity for a period of observation to demonstrate deterioration overtime.

Antenatal vs. postnatal followup

The frequency of ante-partum follow-up of a pregnant mother is leftto the discretion of the obstetrician. While antenatal hydronephrosis(AHN) is more common in fetuses with serious chromosomal anomalies, mostsources do not recommend routine karyotyping for all cases of isolatedAHN. However, this may be considered in the presence of multiple systemanomalies (1). Second trimester AHN is often followed up so thatprogression of severity can be detected and appropriate postnatalfollow-up planned. Cases with severe bilateral AHN and/oroligohydramnios raise concern over potential renal failure and are oftenreferred to the pediatric urologist for antenatal counselling. Otherconcerning sonographic findings include renal corticalhyper-echogenicity, renal cortical cysts and a dilated bladder. Theevaluation and selection of cases for in utero intervention is beyondthe scope of this guideline, but treating physicians should be awarethat many tertiary care centers offer interventions, such asvesico-amniotic shunting in selected cases of bladder outlet obstructionin the setting of multidisciplinary teams. The impact of prenataldiagnosis of HN is also a subject of lengthy discussion; one is referredto the excellent reviews by Thomas (3, 4).

Postnatal resolution has been noted in 25-50% of AHN cases (1, 16).Of those persisting postnatally the majority will be low grade (Table3). In view of this, most centres will refer cases for postnatalevaluation if the third trimester APD is greater than 7mm, despite thefact that greater than 4mm is considered abnormal by definition. Lee etal in a meta-analysis demonstrated that antenatal APD greater than 15mmin the third trimester predicted an 88% chance of postnatalpathology(14). An association between higher rates of postnatalpathology and severity of HN holds true for most HN diagnoses, with theexception of VUR. VUR rates among patients with mild, moderate, andsevere prenatal HN are not significantly different(14). Similarly, Diaset al have shown that if prenatal APD is >18 mm in the 3rd trimesterand >16 mm postnatally, the sensitivity and specificity of thesecut-off values to identify infants who would eventually requirepyeloplasty for UPJO were 100% and 86%, respectively (17).

What are the postnatal investigations?

Clinical examination

Thorough physical examination should specifically include verifyingthe presence of a palpable kidney or bladder, abdominal wallabnormality, signs of spina bifida occulta, a normal introitus infemales and in males the presence of gonads and a normal urethra. Abaseline urinalysis can be useful in the infant follow-up period andwhen the child is non-verbal and unable to express symptoms of a urinarytract infection (UTI), though the need for bag specimens introduces ahigh risk of contamination. Serum creatinine is indicated in cases ofsevere bilateral HN or abnormal renal echogenicity, similarly in asolitary kidney. Serum creatinine should be obtained after 2 days toavoid confusion with maternal creatinine.

Renal--bladder ultrasound (RBUS)

All children with AHN should have a complete abdomino-pelvicultrasound with particular attention to both the kidneys and bladder.One of the most common oversights is to focus merely on the kidneys,likely due to the fact that many radiology requisition forms separatethe abdomen and pelvic ultrasounds. The RBUS should include assessmentof cranio-caudal length of the kidneys, degree of echogenicity andcortico-medullary differentiation, SFU grade of hydronephrosis, maximalAPD on transverse axial view of the renal pelvis, diameter of bothproximal and distal ureter if dilated, the degree of bladder filling,the detrusor thickness or presence of bladder trabeculation,diverticula, ureterocele and posterior urethral dilation in males.

A full bladder should prompt a period of observation withre-imaging post void to assess for the capability to empty the bladderand to assess whether the HN improves post void. The state of bladderfilling should especially be noted on serial ultrasounds and compared tothe previous study when worsening HN is detected (19). Similarly,comparisons of renal length or APD between serial studies should beconsistent with the patient positioning, as the prone views can differfrom the supine or decubitus views (20). Fasting for a RBUS is bothunnecessary and unpleasant.

Timing of the first postnatal ultrasound has been studied in alimited fashion, yet the practice standard has become to avoid doing anUS in the first 2 days of life due to a concern of understagingsecondary to neonatal oliguria (1, 21). Others have studied this issueand have not confirmed the findings(22). Certainly, in cases such as PUVwhere immediate postnatal management is required, there is no reason todelay the US. The acceptable delay in the timing of the first postnatalultrasound is controversial with the SFU suggesting anywhere from 1 to 4weeks. The timing of this study depends to a certain degree on thetreating physician's attitudes to detecting asymptomatic VUR. Inthe absence of a desire to detect such VUR, it is intuitive thatantenatal high-grade HN (HGHN, SFU grades 3-4) should be imaged soon soas to establish a baseline for serial comparison whereas low-grade HN(LGHN, SFU grades

1-2) can be imaged at a greater time interval. On the other hand,families are greatly reassured by a timelier investigation. In addition,the postnatal ultrasound may reveal subtle findings such as poorcortico-medullary differentiation, a ureterocele or detrusor hypertrophywhich can easily be missed when imaging a moving fetus.

Voiding cysto-urethrography

Technical considerations are important and often overlooked incentres not accustomed to the evaluation of children (23). The studyshould include a scout view for assessment of spine anomalies and thepresence of significant constipation or urinary stones. A ballooncatheter should not be used as the balloon can obscure the fillingdefect characteristic of a ureterocele. The amount of urine removedshould be recorded and the urine sent for analysis and culture asindicated. The bladder should be gravity filled until the first voidoccurs, with recording of the obtained bladder capacity. Voiding viewsof the urethra with postvoid views of the bladder are needed. Delayedimaging after the postvoid image may be required if there is VUR into adilated renal pelvis or ureter so as to assess for concomitant UPJO andUVJO. A cyclical study with at least 2 fill and void cycles willincrease the detection of VUR (24). Nuclear cystography is moresensitive for VUR with less radiation exposure and is generallyrecommended for surveillance studies or, where indicated, siblingscreening.

The purpose of a VCUG is to assess for the precise cause of AHN,and is especially helpful in excluding entities such as VUR,ureteroceles and urethral anomalies such as PUV. Historical practicepatterns at the onset of the era of maternal ultrasonography in the1980s were to evaluate all infants with AHN both VCUG and nuclearrenography, due to concerns over obstructive nephropathy and UTI. Withexperience, the yield of such studies and the natural history werebetter understood (14). On average, 16% of infants with AHN are found tohave VUR, with 25% of such cases occurring in the non-dilatedcontralateral renal unit (25). In this meta-analysis, the prevalence ofVUR in a non-dilated kidney was 4%, suggesting this may be the normalprevalence of VUR in the human infant. Szymanski et al compared a groupof children with AHN screened with VCUG to a group managed withobservation and demonstrated that the incidence of UTI was 1% in LGHN(SFU Grades 1 and 2) and occurred exclusively in the group who underwentVCUG (26). In this cohort, the incidence of UTI was 3-fold higher in theHGHN group (SFU Grades 3 and 4) than in the LGHN group, suggesting thatthe grade of HN was a more important risk factor for UTI than VUR. Ofnote, children with bladder anomalies or renal anomalies apart fromisolated HN were excluded from the study.

Certainly, any infant with suspected bladder outlet obstruction(e.g. PUV) should have an urgent VCUG. Bladder outlet obstruction wouldbe suspected with findings of megacystis, thick or trabeculateddetrusor, bilateral HGHN or dilated posterior urethra. This suspicion isamplified with findings of increased renal cortical echogenicity, renalcortical cysts or a history of oligohydramnios.

It is important to note that the clinical utility of a VCUG in HGHNis not due to concern over UTI, rather it helps to distinguish anobstructive cause of AHN from one due to VUR, thus helping to tailor thefrequency and type of serial imaging studies. The American UrologicalAssociation (AUA) guidelines panel on VUR similarly recommends that VCUGbe performed in infants with HGHN, hydroureter or bladder anomalies(25).

Diuretic renography

The current imaging test of choice for the assessment of thefunction of a hydronephrotic kidney is the MAG3 diuretic renogram, as itpermits assessment of both the differential renal function (DRF) and thedrainage time. Technical considerations can alter the test results,hence a standardized protocol is important in permitting comparisons ofserial studies. The "well-tempered renogram" was firstdescribed in 1992 by the SFU and the Society for Nuclear Medicine (SNM)(27). The protocol includes hydration to stress the urinary collectingsystem and bladder catheterization to avoid artifacts due to a fullbladder. The SNM revised their guidelines in 2008 (28) and to this daysignificant differences exist compared to the protocol from the EuropeanAssociation of Nuclear Medicine (29). These different protocols havebeen compared experimentally and can lead to different interpretationsof the results (30). This highlights the importance of comparing serialstudies only if they were performed with the same institutionalprotocol.

The diuretic renogram should include a report of the DRF, which canvary between 45-55%, the cortical transit time which is normal up to 5minutes, the half-time and the shape of the curve (31). Test results canbe influenced by poor renal function (single kidney GFR < 15 ml/min),poor hydration, massively dilated collecting system, full bladder and adilated distal ureter (32).

Familiarity with the history of diuretic renography helps inunderstanding current controversies over the timing of this test.Diuretic renogram definitions of obstruction were first introduced inpatients with symptomatic UPJO or a positive Whitaker test (33). Whenmaternal ultrasonography was introduced and antenatal hydronephrosis wasdiscovered, the same criteria were initially applied; with time therealization occurred that too many infants were having unnecessarypyeloplasties. In the early 1990s two landmark series of theconservative management of AHN arose which contributed to 2 schools ofthought. In the Ransley group, renograms were done at 4 weeks of lifedue to concerns over false positive studies with immature neonatal GFR.Pyeloplasty was indicated on the basis of a single study with initialpoor split function (<40% DRF) (34). In the Koff study, renogramswere performed at the time of diagnosis, regardless of age and allpatients were given a chance at observation (35). The purpose of thefirst renogram was to serve as a baseline for serial comparison, thethinking being that drainage times would improve with renal maturation.The follow-up interval was tailored to the severity of the initially DRFin cases with low initial split function. It is interesting to note thatthe Koff group suffered no irreversible loss of function withobservation whereas the Ransley group had a 9% renal deterioration rate.In conclusion, renograms can be performed at any age, as long as theyare used as a baseline study for serial comparison. One should alsoconsider a DMSA study to establish early split function in cases ofneonates or premature infants, since the DRF in this study is notinfluenced by an immature GFR (36).

Ancillary tests

Additional studies are sometimes necessary to further elucidate theprecise cause of ANH, which because of their invasive nature arereserved for only select cases. Percutaneous antegrade pyelography orendoscopic retrograde pyelography can be useful when multiple levels ofobstruction are suspected, such as combined UPJO and UVJO. Cystoscopycan help for evaluation of ectopic ureters and ureteroceles, similarlymagnetic resonance urography (MRU). MRU can be especially helpful withthe abnormal anatomy found in duplication anomalies, renal ectopy andrenal fusion anomalies. This type of abnormal anatomy is often found inchildren with the VACTERL association or cloacal anomalies. Non-invasivestudies such urinary biomarkers such as transforming growth factor betaare still under investigation, but hold promise in predicting thosecases who would deteriorate and require closer follow-up (37).Similarly, the field of functional renography holds promise both withnuclear medicine (38) and positron emission tomography (39). GFR renalscan may be helpful in cases of severe bilateral HN.

Continuous antibiotic prophylaxis (CAP)

CAP has empirically been recommended for newborns with prenatal UNin an attempt to reduce the rate of UTI during the first two years oflife. However, the AUA, the SFU and the CUA all acknowledge that use ofCAP for prevention of UTI in infants with prenatal HN has been based onlow levels of evidence. Not surprisingly, this lack of high-qualityevidence has resulted in practice variability for CAP use. According tothe 2010 SFU consensus statement on HN, CAP should be recommended onlyfor infants with high-grade HN and those with VUR(1).

Given the uncertainty over CAP use in prenatal HN patients, asystematic review was conducted in 2013 to summarize the latest evidenceregarding CAP use in children with prenatal HN. Data of nearly 4000patients from 21 full-text articles demonstrated that pooled UTI rateswere four times higher for high-grade HN patients when compared to thosewith low-grade HN. In children with low-grade HN, UTI rates wereequivalent, regardless of their CAP status (2.2% on CAP vs. 2.8% not onCAP). On the contrary, high-grade HN patients on CAP experienced fewerUTIs than those not on CAP (14.6% vs. 28.9%; p<0.01), suggesting thatCAP may be beneficial in this population. The estimated number needed totreat was seven, meaning that a clinician would offer CAP to sevenpatients with high-grade HN in order to prevent one UTI(40). A morerecent systematic review confirmed that there seems to be value inproviding CAP to infants with high-grade HN (41).

The suggestion has also been made that the presence of hydroureteror ureterocele carry a higher risk of UTI (Table 4).

The subgroup of patients with primary non-refluxing megaureters(hydroureteronephrosis) has been studied in greater detail. Theseinfants had a much higher febrile UTI rate than those with isolated HN[19/59 (32%) vs. 12/218 (6%)] according to a prospective study(43).Moreover, another study demonstrated that febrile UTIs developed in 34%of megaureter patients within the first 6 months of life and thatcircumcision and CAP significantly decreased their infection rates(44).Other studies with retrospective design have reported similarfindings(45). In addition, females and uncircumcised males with prenatalHN have also exhibited a much higher risk of UTIs(46).

The role of prophylactic antibiotics in children with prenatal HNwho are awaiting completion of postnatal investigations iscontroversial. While it is believed that CAP may prevent UTI in childrenwith prenatal HN, it has yet to be proven. A randomized controlled trialcomparing trimethoprim to placebo in infants with SFU grades III-IV HNis currently underway in order to answer this question (47). Therefore,some authors suggest institution of CAP at birth, while others, instead,recommend a low threshold for investigation and treatment of a suspectedUTI. Commonly used prophylaxes in the neonate include amoxicillin,cephalexin and trimethoprim. Trimethoprim-sulfamatholxazole andnitrofurantoin should NOT be used in the neonate because of therespective risk of kernicterus and hemolytic anemia.

Followup protocols

SFU Grades 3 and 4, APD >15 mm, HGHN

The initial postnatal RBUS should be done as soon as feasible afterday 2 of life, as this represents the cohort most likely to requiresurgery and to experience UTI. The likelihood of grade 4 HN undergoing apyeloplasty is up to 75%(35). Most centres recommend the US within 2weeks of life. Bilateral HGHN requires more urgent consultation,including a VCUG to exclude PUV. If the postnatal US reveals persistentHGHN, these cases should be referred to a Pediatric Urologist forimmediate consultation. These cases are most likely to benefit from CAPand should have both a VCUG and MAG3 renal scan. It is worth repeatingthat the clinical utility of a VCUG in HGHN is not due to concern overUTI, rather it helps to distinguish an obstructive cause of AHN from onedue to VUR, thus helping to tailor the frequency and type of serialimaging studies. In the absence of any pathology requiring immediateintervention, repeat US and MAG3 should be performed within 3 months,though a repeat MAG3 is optional if the first exam is normal(Algorithm). Close follow-up should continue if improvement is not seen,to at least 18 months of age by which time most childhood UPJO becomesapparent. One should keep in mind that historical cohorts of symptomaticUPJO prior to the advent of maternal ultrasonography would undergopyeloplasty at an average age of 6 years (2), hence a persistent grade 3HN requires active surveillance.

SFU Grade 1 and 2, APD <10 mm, LGHN

The timing of the first postnatal US is open to debate and left tothe discretion of the treating physician. For cases with antenatal APDbetween 10-15 mm the SFU grading is suggested to clarify which follow-upprotocol should be used. Most physicians will obtain an ultrasoundwithin the first months of life and a follow-up can be obtained 6 monthslater. In the absence of deterioration, follow-up US can then beperformed on an annual basis. VCUG and Mag3 are not required. Szymanskiet al demonstrated the risk of UTI in isolated LGHN with no renal sizediscrepancy and no ureteral or bladder abnormalities to be less than 1%(26), hence CAP is unnecessary. The majority of such cases improve by 2years of age (48). Since the majority of congenital UPJO progresses topyeloplasty by 18 months of age it seems prudent to continue thefollow-up to at least such an age. Multiple authors have shown that withlong-term follow-up to 10 years the risk of deterioration requiringsurgical intervention to be 2% (49, 50). The question then arises as tothe need for follow-up beyond 2 years of age in patients who havepersistent LGHN. Some authors recommend discharge and counsel familieson the symptoms of UPJO. Future prospective studies will be needed todetermine the most cost-effective and clinically appropriate follow-upprotocol for children with prenatal HN. Akhavan et al. have looked atthe resource utilization associated with the diagnostic evaluation ofnonrefluxing HN infants and found that decreasing the number of USperformed during follow-up for patients with SFU grades I-II HN couldreduce 24% of the health care costs(51).

SFU Grade 0

Up to 50% of AHN can resolve at birth and is referred to as SFUGrade 0 HN. Such transient HN is also the subject of controversy withthe SFU guidelines recommending a repeat US within the first month oflife (1). Many centres will discharge the patient after a normalpostnatal US, since the majority of late or recurrent HN are symptomaticand can be counselled of such. Certainly, it appears contradictory tofollow-up a documented LGHN within 6 months whereas a normal US isfollowed-up within 1 month.

Indications for surgery in obstructive HN and HUN

The current difficulty in proving the presence of obstruction in HNand HUN imply that a period of observation is needed to documentdeterioration. This period of observation carries a risk of potentiallyirreversible loss of renal function (52). For this reason, appropriatecounselling of families should include a discussion of the risks ofobservation versus immediate surgery. Strong indications forreconstructive surgery include loss of DRF of greater than 5% on serialrenography or worsening HN with worsening drainage times on renography.In older children flank pain or vomiting are also suggestive ofobstruction, especially if exacerbated by fluid intake. Hypertension andrenal calculi can rarely be signs of obstruction. Relative indicationsfor surgery include UTI, low DRF on initial renogram, palpable giant HN,concern over noncompliance with follow-up imaging protocols and familypreference in cases of persistent HGHN requiring repeated renographicevaluation. In one study an alarming 42% of children with HGHN were lostto follow-up (53). The threshold for surgical intervention is lowered incases of solitary kidney or bilateral HGHN.

Summary of recommendations

(1.) All significant AHN should be investigated with a postnatalRBUS. Most centres define significant AHN in the third trimester as APD[greater than or equal to] 7 mm (Level 3 evidence; Grade Crecommendation).

(2.) The role of CAP initiated at birth is controversial, but maybe of greater benefit in grades 3 and 4 HN and in cases with dilatedureter or bladder abnormality. Females and uncircumcised males with AHNmay also benefit more compared to circumcised boys (Level 3 evidence;Grade C recommendation).

(3.) VCUG is not necessary in the evaluation of isolated low grade(SFU 1 and 2) HN with normal renal parenchyma and symmetric renal size(Level 3 evidence; Grade C recommendation).

(4.) High grade HN (SFU III-IV) should be investigated with a VCUG,followed by diuretic renography if the HN cannot be explained by VUR(Level 4 evidence; Grade D recommendation).

(5.) Diuretic renography is not necessary in the evaluation ofisolated low grade (SFU 1 and 2) HN with normal renal parenchyma andsymmetric renal size (Level 4 evidence; Grade D recommendation).

Table of Abbreviations:

HN--Hydronephrosis

AHN--Antenatal hydronephrosis

SFU--Society for Fetal Urology

HGHN--High grade HN, SFU Grade 3-4

LGHN--Low grade HN, SFU Grade 1-2

APD - Antero-posterior renal pelvic diameter

UPJO--Uretero-pelvic junction obstruction

UVJO--Uretero-vesical junction obstruction

VUR--Vesicoureteric reflux

PUV--Posterior urethral valve

RBUS--Renal-bladder ultrasound

VCUG--Voiding cysto-urethrogram

DRF--Differential renal function

CAP--Continuous antibiotic prophylaxis

MAG3 - Tc-99m mercaptoacetyltriglycine

DMSA- Dimercaptosuccinic acid

PUC--Pediatric Urologists of Canada

CUA--Canadian Urological Association

AUA--American Urological Association

UTI--Urinary Tract Infection

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Figures and Tables

John-Paul Capolicchio, MD (1); Luis H. Braga, MD (2); Konrad M.Szymanski, MD, MPH (3)

(1) Montreal Children's Hospital, McGill University HealthCentre, Montreal, QC, Canada; (2) McMaster Children's Hospital,McMaster University, Hamilton, ON, Canada; (3) Riley Hospital forChildren at Indiana University Health, Indianapolis, IN, United States

Cite as: Can Urol Assoc J 2017 Dec. 22; Epub ahead of print.

http://dx.doi.org/10.5489/cuaj.5094

Published online December 22, 2017

Caption: Fig. 1. Algorithm for management of antenatalhydronephrosis.

Table 1. SFU grading of hydronephrosisSFU grade Ultrasound findings0 Normal kidney (resolved antenatal hydronephrosis)1 Pyelectasis2 Pyelectasis with dilation of 1 or more major calyces (caliectasis)3 Pyelectasis with dilation of all 3 major calyces4 Pyelectasis with parenchymal thinning compared to contralateral kidneySFU: Society for Fetal Urology.Table 2. Severity of antenatal hydronephrosis (ANH) by APDDegree of ANH Second trimesterMild 4 to <7 mmModerate 7 to [less than or equal to] 10 mmSevere >10mmDegree of ANH Third trimesterMild 7 to <9 mmModerate 9 to [less than or equal to] 15 mmSevere >15 mmAPD: antero-posterior renal pelvic diameter.Table 3. Distribution of antenatal hydronephrosis (ANH) severity andlikelihood of postnatal urinary tract pathology (18)Degree of ANH % of ANH % postnatal pathologyMild 57-88 12Moderate 10-30 45Severe 1.5-13 88Table 4. Incidence of urinary tract infections (UTIs) in patients withhydronephrosis No. UTI (%) P OR 95% CISex Male 67 (19) 0.8 0.93 0.51-1.71 Female 16 (20)Obstruction Yes 50 (39) 0.001 5.23 3.148-8.67 No 33 (11)Hydroureter Yes 37 (47) 0.001 6.00 3.49-10.32 No 46 (13)Uretetocele Yes 10 (59) 0.001 6.65 2.45-18.06 No 73 (18)HN grade I 6 (4) II 13 (14) 0.001 4.15 1.52-11.32 III 26 (33) 0.001 12.67 4.95-32.47 IV 38 (40) 0.001 16.93 6.80-42.15

Please Note: Illustration(s) are not available due to copyrightrestrictions.