Management of neonatal hydronephrosis diagnosed in antenatal period
By:
Dr behzad barekatain,MD
Assistant professor of pediatrics
Neonatologist
Isfahan university of medical sciences
INTRODUCTION
Fetal hydronephrosis (dilatation of the renal pelvis collecting system) is
most common congenital finding by prenatal ultrasonography and is
readily diagnosed finding on antenatal ultrasound examination occuring
in 0.5 to 4.6 percent of pregnancies
It can be detected as early as the 12th to 14th week of gestation
Although renal pelvic dilatation is a transient, physiologic state in most
cases, urinary tract obstruction and vesicoureteral reflux (VUR) can
occasionally be causal. These conditions can prevent normal renal
development and/or cause renal injury
However, the majority of cases of antenatal hydronephrosis are not
clinically significant leading to unnecessary testing of the newborn baby
and anxiety for patients and healthcare providers
The goal of prenatal management is to detect those cases of antenatal
hydronephrosis that will impact the health of the infant and require
antenatal and postnatal evaluation, timely referral to a pediatric urologist
if required, and possible intervention to minimize adverse outcomes
DEFINITION AND GRADING
Several systems have been developed to diagnosis and grade the severity
of antenatal hydronephrosis
Scoring systems differ based upon the fetal ultrasound criteria used, as
follows:
1.Society of Fetal Urology (SFU) criteria
SFU criteria for the diagnosis and grading of antenatal hydronephrosis
are based upon the
1.degree of pelvic dilation
2. presence of caliceal dilation
3.the presence and severity of parenchymal thinning or atrophy.
The SFU developed criteria for the diagnosis and grading of antenatal
hydronephrosis based upon the degree of pelvic dilatation, number of
calyces seen, and the presence and severity of parenchymal atrophy .
• Grade 0 — Normal examination with no dilatation of the renal pelvis
• Grade 1 — Mild dilatation of the renal pelvis only
• Grade II — Moderate dilatation of the renal pelvis including a few
calyces
• Grade III — Dilatation of the renal pelvis with visualization of all the
calyces, which are uniformly dilated, and normal renal parenchyma.
• Grade IV — Similar appearance of the renal pelvis and calyces as
Grade III plus thinning of the renal parenchyma.
2.Renal pelvic diameter
Measurement of the maximum anteroposterior diameter of the renal
pelvis (APPD), also referred to as renal pelvic diameter (RPD), is the
most generally accepted method to define antenatal hydronephrosis .
Several studies have established normative data for fetal renal size based
upon gestational age . However, despite these data, there remains a lack
of consensus on the threshold RPD that defines clinically significant
antenatal hydronephrosis.
Renal pelvic diameter (RPD)
Although there is a lack of consensus on the threshold RPD that defines
antenatal hydronephrosis, hydronephrosis is graded according to the
RPD during the second and/or third trimester of pregnancy.
2th trimester
3th trimester
postnatal
normal:<7 mm
7-8 mm
mild
4-7 mm
<9 mm
moderate
7-10 mm
9-15 mm
9-15 mm
severe
>10 mm
>15 mm
> 15 mm
3.Changes in the degree of hydronephrosis
The relative change in hydronephrosis compared to subsequent prenatal
ultrasound or the first postnatal ultrasound has been used in the clinical
research setting . However, testing its clinical applicability has been
limited. As a result, relative changes in antenatal hydronephrosis are not
generally used clinically.
Despite numerous studies in neonates with antenatal hydronephrosis ,
there remains considerable debate on the accepted RPD threshold that
predicts clinically significant disease in the neonate.
Currently, no criteria have been identified that can identify all neonates
with significant pathology and exclude those infants with transient or
physiologic hydronephrosis.
Thus, although a low threshold (eg, RPD >4 mm) in the second trimester
will have a greater sensitivity of detecting infants with CAKUT, it would
also include a large number of patients without renal disease who would
undergo unnecessary testing.
A high risk of poor prognosis and early-onset renal failure can be
predicted from the following features:
1.Detection of dilatation before 24 weeks of gestation
2.Male fetus
3.Distended and/or thick-walled bladder
4.Moderate or severe upper tract dilatation
5.Abnormal renal parenchyma: microcystic or ‘bright’ parenchyma on
ultrasound
6.Oligohydramnios
EPIDEMIOLOGY
.Hydronephrosis occurs approximately twice as often in males than in
females.
.It is bilateral in 20 to 40 percent of cases.
.The reported incidence of antenatal hydronephrosis ranges from 0.6 to
4.5 percent of pregnancies. Differences in reported data may be due to
different criteria used to define the disorder and the level of attention to
the urinary system by the ultrasonographer .
ETIOLOGY
.In a one review, causes of antenatal hydronephrosis and their relative
frequency were determined as follows :
• Transient — 48 percent
• Physiologic — 15 percent
• UPJ obstruction — 11 percent
• VUR — 9 percent
• Megaureter — 4 percent
• Multicystic dysplastic kidney — 2 percent
• Ureterocele — 2 percent
• Posterior urethral valves — 1 percent
Less common causes included ectopic ureter, prune belly, urachal cyst,
duplex collecting system and urethral atresia
PRENATAL ISSUES
Detection of antenatal hydronephrosis usually occurs in the second
trimester with a RPD cutoff of ≥4 mm. Mild hydronephrosis (RPD of 4
to 9 mm or SFU grade 1 or 2) can be associated with Down syndrome
and an increased risk of other chromosome anomalies. More severe
dilatation increases the risk of renal/urinary tract disorders.
Down syndrome — Mild hydronephrosis is a common finding in fetuses
with Down syndrome. Studies that defined hydronephrosis as RPD ≥4
mm demonstrated hydronephrosis is greater in Down syndrome
compared to normal control fetuses (18 versus 0 to 3 percent,
respectively).
The finding of mild hydronephrosis requires a detailed assessment of
fetal anatomy and review of clinical risk factors for Down syndrome.
However, genetic amniocentesis is not warranted based solely on the
isolated finding of hydronephrosis, because the incidence of Down
syndrome remains low (<1 in 300 pregnancies) in fetuses with no
maternal risk factors (eg, advanced age or abnormal maternal serum
screen) or without any other sonographic features suggestive for Down
syndrome
The likelihood that an infant postnatally will have a significant CAKUT
increases with the severity of hydronephrosis.This was illustrated in a
meta-analysis of 1678 infants that demonstrated that the severity of
antenatal hydronephrosis defined by RPD increased the risk of
renal/urinary tract pathology, as follows:
• Mild hydronephrosis (≤7 mm in the second trimester and/or ≤9 mm in
the third trimester) — 12 percent
• Moderate hydronephrosis (7 to 10 mm in the second trimester and/or 9
to 15 mm in the third trimester) — 45 percent
• Severe hydronephrosis (>10 mm in the second trimester and/or >15
mm in the third trimester) — 88 percent
Timing of prenatal ultrasonography is important in optimal detection of
CAKUT.
Ultrasonography performed before the 18 to 24th week of gestation can
fail to detect significant disease . In addition, studies performed in the
third trimester have been suggested to be more helpful in predicting
postnatal outcome than screening earlier in the pregnancy. Thus, most
authors agree that a repeat scan in the third trimester (28 to 34 weeks
gestation) be performed to identify those fetuses potentially requiring
postnatal intervention
Ultrasound follow-up
.Fetuses with mild hydronephrosis should have a follow-up ultrasound
scan in the third trimester (32 to 34 weeks of gestation). Those with
resolution have a low risk of clinically significant pathology, and do not
need further antenatal or postnatal evaluation.
.By comparison, serial follow-up ultrasounds are indicated for fetuses
with:
- Moderate or severe hydronephrosis
- Bilateral involvement
- Progression and/or persistence of hydronephrosis
- Oligohydramnios
.The interval for follow-up examination and management are dictated by
the initial findings and the amount of amniotic fluid.
.If fetal hydronephrosis is detected, the following parameters need to be
evaluated by ultrasonography as they guide further need for evaluation
and are helpful in determining the cause of hydronephrosis:
• Severity of hydronephrosis
• Unilateral versus bilateral involvement
Bilateral involvement increases the risk of a significant abnormality and
the risk of impaired postnatal renal function.
• Ureter
Dilatation of the ureter can be consistent with VUR or obstructive
uropathy distal to the ureteropelvic junction [eg, ureterocoele,
megaureter, or posterior urethral valves (PUV)].
• Bladder
Abnormalities of the bladder such as increased thickness and
trabeculation of the bladder wall are consistent with obstructive uropathy
distal to the bladder (eg, PUV). In addition, dilatation of the proximal
urethra (key-hole sign) may indicate PUV in male fetuses patients with a
thickened bladder wall and hydronephrosis .
• Amniotic fluid
Oligohydramnios is consistent with impaired renal function resulting in
a decreased production of fetal urine (amniotic fluid). It is a consistent
feature of severe renal disease affecting both kidneys or a solitary kidney.
• Renal parenchyma
Thinning of the parenchyma indicates injury or impaired development of
the renal cortex. An echogenic renal cortex may indicate abnormal renal
parenchymal development (dysplasia), which may be associated with
vesicoureteral reflux.
Other anomalies
.Other non-renal/urinary tract congenital abnormalities are associated
with antenatal hydronephrosis.
.In one case series of 104 fetuses with hydronephrosis, the three other
major birth defects detected were ventricular septal defect in a patient
with Down syndrome, microcephaly and omphalocele .
.Hydronephrosis also has been reported as part of a multiple
malformation syndrome in more than 60 genetic and sporadic
malformation syndromes .
.In one case series, a chromosomal abnormality was detected in 7 of 81
fetuses that had karyotyping . Of those, only two had isolated renal
malformations.
OVERVIEW OF MANAGEMENT
Decisions regarding evaluation and care are dependent on the:
1. presence and nature of associated renal and extrarenal anomalies
2. severity of hydronephrosis
3. unilateral versus bilateral involvement
4. gestational age
5. the amniotic fluid volume
Antenatal management:
In fetuses with mild hydronephrosis and normal amniotic fluid, a careful
examination for genitourinary and extrarenal abnormalities should be
performed.
Clinical risk factors and ultrasound markers of Down syndrome should
be evaluated.
Assessment of the fetal karyotype should be offered if additional fetal
anomalies are detected, in women of advanced maternal age, and women
with abnormal maternal serum screening tests for Down syndrome.
Post natal management:
Evaluation includes:
1.physical examination
2. use of radiologic studies to detect renal and urinary tract
abnormalities including obstructive uropathy or vesicoureteral
reflux (VUR).
.Currently, there is not a single test or finding that accurately
differentiates infants with significant disease from those who are
normal or have insignificant findings.
.In practice, usually use an algorithm based upon the presence of
predicative factors (bilateral involvement and severity of
hydronephrosis) for postnatal management that limits unnecessary
radiographic studies and minimizes parental distress.
PHYSICAL EXAMINATION
.The physical examination of the newborn can detect abnormalities that
suggest genitourinary abnormalities associated with antenatal
hydronephrosis. These include the following:
1. The presence of an abdominal mass that could represent an enlarged
kidney due to obstructive uropathy or multicystic dysplastic kidney
(MCDK).
2.Potter apearance
The facies results from oligohydramnios
causing prolonged intrauterine
compression on the entire face. The nose is
flattened, there are large vertical creases
below the eyes, the ears are low set and
dysplastic, and there is mild micrognathia.
Note the flattening of the nose and
the low-set ears. Pressure deformity from
the oligohydramnios
Infant with Potter facies and arthrogryposis due to
oligohydramnios
This infant with sirenomelia (“mermaid fetus”) has the typical
Potter facies, as renal agenesis with resulting oligohydramnios is
always present.
Sirenomelia is characterized by fusion of all or part of the lower
limbs and is a condition incompatible with life.
3.A palpable bladder in a male infant, especially after voiding, may
suggest posterior urethral valves.
palpable bladder in a male infant with posterior urethral valves
Autopsy specimen of the infant with
congenital posterior urethral valves.
Note the urethral valves, enlarged
bladder,bilateral hydroureter, and
bilateral hydronephrosis.
Huge distended ureters and
hydronephrotic kidney
4. A single umbilical artery is associated with an increased risk of
CAKUT, particularly vesicoureteral reflux.
5.supernumerary nipples
6. The presence of outer ear abnormalities are associated with an increased
risk of congenital anomalies of the kidney and urinary tract (CAKUT).
7. A male infant with prune belly syndrome will have deficient
abdominal wall musculature and undescended testes. The presence
of associated anomalies should be noted.
Currently it is thought that the marked
distention of the bladder and ureters and
renal involvement result in the ablation of
the abdominal muscles, especially the recti.
The kidneys may be hypoplastic or severely
hydronephrotic as a result of the
obstruction.
Autopsy specimen in an infant with the prune belly syndrome
showing the marked bulging of the flanks, lack of abdominal
muscles, and bilateral polycystic kidneys
8.ascit
Marked abdominal distention in an infant with urinary ascites and
bilateral multicystic kidneys
Transillumination of the abdomen showing the large amount
of ascitic fluid.
9.amnion nodosum
Fetal surface of the placenta
showing amnion nodosum.
Note the small nodules which occur
as a result of the oligohydramnios.
The nodules consist of vernix
caseosa,lanugo, and squamous
epithelial cells from the fetal skin
(A) Urethral agenesis with megacystis and huge bilateral urethral
diverticula (arrows) in fetus of 27 weeks gestation (UB, urinary
bladder).
X-ray of (A) showing massively distended bladder and bilateral
ureteral diverticula.
RADIOLOGIC STUDIES
.Postnatal radiologic evaluation of a newborn with antenatal
hydronephrosis begins with an ultrasound examination.
.The timing of ultrasonography and the need for other studies depend
upon:
1.the severity of antenatal hydronephrosis
2. whether there is bilateral involvement (or an affected solitary
kidney) or unilateral involvment.
Ultrasonography
.Affected infants should have an ultrasound examination of the
kidneys and bladder in the postnatal period.
.The timing of the study depends upon the severity of the
antenatal hydronephrosis.
.In general, examination should be avoided in the first two days
after birth because hydronephrosis may not be detected
because of extracellular fluid shifts that will underestimate the
degree of hydronephrosis.
.However:
1.infants with bilateral hydronephrosis
2.those with a severe hydronephrotic solitary kidney
require urgent evaluation on the first postnatal day because of
the increased likelihood of significant disease and a possible
need for early intervention.
.For unilateral hydronephrosis without antenatal bladder
pathology, we recommend that the postnatal sonogram be
done at one to four weeks after birth.(in some refrence 1014th day after birth)
Voiding cystourethogram
.A voiding cystourethogram (VCUG) is performed to detect VUR
and in boys, to evaluate the posterior urethra.
.For this procedure, a urinary catheter is inserted into the bladder and
contrast material is instilled. Fluoroscopic monitoring is performed
while the bladder is filling and during voiding. Although the
duration of fluoroscopy is minimized, the gonads, especially the
ovaries, are exposed to radiation .
The role of the VCUG in the routine postnatal evaluation of infants
with prenatally detected dilatation remains controversial, with
practice varying considerably between different centres.
However, the following conditions are generally regarded as being
definite indications for a postnatal VCUG:
1.abnormal bladder (particularly a thick-walled bladder or other
evidence of outflow obstruction)
2. bilateral upper tract dilatation
3.dilatation of one or both ureters seen on either on pre- or postnatal
ultrasound
4. duplex kidneys (in view of the high incidence of lower pole
reflux).
the VCUG is an invasive and potentially distressing procedure
which carries some risk of morbidity in its own right
(predominantly infection). For these reasons, many
neonatologist no longer advocate routine VCUG if dilatation
is confined to the renal pelvis (i.e. no evidence of ureteric
and/or calyceal dilatation), and the AP diameter of the pelvis
is <15 mm.
Some cases of low-grade VUR will be missed by this approach,
but this is outweighed by the benefit of a greatly reduced
burden of unnecessary investigation into healthy infants.
If an VCUG is not undertaken, the child’s parents and general
practitioner should, nevertheless, be alerted to the importance
of having the urine checked for possible infection in the
event of an unexplained febrile illness or more specific
features of urinary infection.
cystogram
with posterior urethral valves shows extensive vesicoureteral
reflux and bilateral hydroureter and hydronephrosis.
Diuretic renography
. Diuretic renography (renal scan and the administration of a
diuretic) is used to diagnose urinary tract obstruction in
infants with persistent hydronephrosis, usually ordered after a
VCUG has demonstrated no vesicoureteral reflux.
. It measures the drainage time from the renal pelvis and
assesses total and each individual kidney's renal function.
.Since the information derived from DMSA scintigraphy or
diuretic renography rarely influences practical management
in the first few weeks or months of life, isotope imaging is
best deferred until 1–3 months of age.
.Renal scintigraphy is used to assess renal anatomy and function. The
two most commonly used radiopharmaceuticals are
1.mercaptoacetyl triglycine (MAG-3)
2.technetium-99m-labeled dimercaptosuccinic acid (DMSA).
. MAG-3, which is excreted by renal tubular secretion, is used to
assess differential renal function, and, when furosemide is
administered, drainage also can be measured.An alternative to
MAG-3 is diethylene tetrapentaacetic acid (DTPA), which is
cleared by glomerular filtration. The background activity of DTPA
is much higher than that of MAG-3.
. DMSA is a renal cortical imaging agent and is used to assess
differential renal function and to demonstrate whether renal
scarring is present. It is used infrequently in children with
obstructive uropathy.
.In a MAG-3 diuretic renogram, a small dose of technetium-labeled
MAG-3 is injected intravenously.
During the first 2–3 min, renal parenchymal uptake is analyzed and
compared, allowing computation of differential renal function.
Subsequently, excretion is evaluated.
After 20–30 min, furosemide is injected intravenously, and the
rapidity and pattern of drainage from the kidneys to the bladder
are analyzed.
a.If no obstruction is present, half of the radionuclide should be
cleared from the renal pelvis within 10–15 min, termed the halflife (t½).
b.If there is significant upper tract obstruction, the t½ usually is >20
min.
c.A t½ between 15–20 min is indeterminate.
.The images generated usually provide an accurate assessment of the
site of obstruction.
. Numerous variables affect the outcome of the diuretic renogram.
1.Newborn kidneys are functionally immature, and, in some cases,
normal kidneys may not demonstrate normal drainage after diuretic
administration.
2.Dehydration prolongs parenchymal transit and can blunt the
diuretic response.
3.Giving an insufficient dose of furosemide may result in
inadequate drainage.
4.If vesicoureteral reflux is present, continuous catheter drainage is
mandatory to prevent the radionuclide from refluxing from the
bladder into the dilated upper tract, which would prolong the
washout phase.
.In response to the numerous variables, the Society for Fetal Urology
and the Pediatric Nuclear Medicine Club jointly developed a
standardized method for performing diuretic renography in infants
and children, termed the well-tempered renogram
.The test requires insertion of a bladder catheter to relieve any
pressure that can be transmitted to the ureters and kidneys.
Intravenous access is needed for hydration and the administration
of the radioisotope and diuretic. The preferred radioisotope is
technetium-99m-mercaptoacetyltriglycine (Tc99mMAG3), which
is taken up by the renal cortex, filtered across the glomerular
basement membrane to the renal tubules, and excreted into the
renal pelvis and urinary tract.
.The study includes two phases:
Initial phase
Radioisotope is injected intravenously and renal parenchymal
(cortical) uptake is measured during the first two to three minutes.
The relative contribution of each kidney to overall renal function
(called the split renal function) is assessed quantitatively and is
useful as a baseline study. Subsequent studies can be compared to
assess whether kidney function remains stable or has deteriorated,
suggesting true obstruction .
Second phase
.In the second phase at peak renal uptake, intravenous furosemide is
administered and the excretion of isotope from the kidney is
measured referred to as the "washout curve". This phase indicates
the extent of obstruction, if present.
.In the normal kidney: the administration of furosemide results in a
prompt washout.
.In a dilated system:
a.if washout occurs rapidly after diuretic administration (<15
minutes), the system is not obstructed.
b.if washout is delayed beyond 20 minutes, the pattern is consistent
with obstructive uropathy.
.However, a delayed washout must be interpreted with caution . As
an example, in a series of 39 infants with antenatal unilateral
hydronephrosis followed without surgery, diuretic renography
indicated obstruction in 24 patients whose renal function never
decreased and thus could not have been obstructed . These results
may be in part be due to the normally low neonatal glomerular
filtration rate that can be refractory to diuretic therapy.
.If washout is between 15 and 20 minutes, the study is indeterminate.
Split renal function
.The split renal function is the most useful criteria to evaluate a
decrease in renal function. In patients with unilateral
hydronephrosis (which is the most common clinical
scenario), if the normal nonhydronephrotic kidney and
hydronephrotic kidney both have equal function,
conservative management without surgery is a safe option.
.In a cohort of 831 cases of antenatal hydronephrosis, renal scans
performed in 229 newborns demonstrated 16 percent of patients
had significant decrease in renal function of one kidney defined as
≤35 percent or less differential renal function.
. A decrease in differential renal function was associated with severe
antenatal hydronephrosis (ie, renal pelvic diameter >10 mm in at
20 to 24 weeks gestation and >16 mm greater than 33 weeks
gestation).
.The characteristics of the uptake and drainage curves, as
defined by O’Reilly and associates, fall into four patterns :
Type 1. Normal uptake with prompt washout.
Type 2. Rising uptake curve; no response to diuretic
(obstruction).
Type 3a. Initially rising curve, that falls rapidly in
response to diuretic (non-obstructive dilatation).
Type 3b. Initially rising curve which neither falls promptly nor
continues to rise.
.Whereas type 1 and type 3a curves are normal and non
obstructed, the clinical significance of type 2 and type 3b
curves remains problematic.
.Drainage curves can be particularly difficult to interpret in the
first few months of life (the period of so-called ‘transitional
nephrology’) when immaturity of the renal tubules may
impair the response of the kidney to diuretic stimulation.
IVP(intra venous pyelogram)
The MAG-3 diuretic renogram is considered superior to the
excretory urogram in infants and children with hydronephrosis,
because bowel gas and immaturity of renal function often cause
the intravenous pyelogram (IVP) images to be suboptimal.
Magnetic resonance urography
.Magnetic resonance urography (MRU) in children is becoming more
commonly used in the diagnosis and management of congenital
uropathies, such as ureteropelvic junction obstruction.
.MRU is especially useful in the management of obstructed kidneys
that have rotation or ascent anomalies, or are solitary.
.MRU can more clearly define the anatomy and delineate the proper
surgical approach (ie, retroperitoneal versus transperitoneal).
.The disadvantage of MRU is that they study often requires a general
anesthesia or heavy conscious sedation in children. Furthermore,
the contrast agent gadolinium can only be used if the renal
function is normal (requiring a preprocedure serum creatinine test)
because of reports of irreversible renal fibrosis in patients with
renal insufficiency.
. Newer MRU technology may even define obstruction, eliminating
the need for diuretic renal scans.
APPROACH
.The goal of evaluation is to identify all infants with significant renal
or urinary tract abnormalities but limit unnecessary radiographic
studies and minimize parental distress in infants with clinically
insignificant findings or normal infants.
. The risk of renal and urinary tract abnormality increases with the
1.severity of hydronephrosis
2.persistence of hydronephrosis into the third trimester
3.bilateral involvement
4.presence of oligohydramnios.
Severe Bilateral hydronephrosis
.Infants with severe bilateral antenatal hydronephrosis and/or bladder
distension are at increased likelihood to have significant disease
.These infants and those with a severe hydronephrotic solitary kidney
should be evaluated initially by ultrasonography on the first
postnatal day
. Bilateral hydronephrosis suggests an obstructive process at the level
or distal to the bladder such as ureterocele or posterior urethral
valves (PUV) in a male infant, which can be associated with
impaired renal function and ongoing renal injury.
.If the postnatal ultrasound demonstrates persistent hydronephrosis, a
VCUG should be performed. In male infants, the posterior urethra
should be fully evaluated to detect possible posterior urethral
valves.
Mild & moderate bilateral hydronephrosis
.Infants with mild or moderate hydronephrosis can be evaluated after
7 days of life.
Severe unilateral hydronephrosis
.In newborns with severe antenatal unilateral hydronephrosis (renal
pelvic diameter >15 mm in the third trimester), ultrasonography
should be performed after the infant returns to birth weight (after
48 hours of age and within the first two weeks of life).
Moderate and mild unilateral hydronephrosis
.In newborns with less severe antenatal unilateral hydronephrosis
(renal pelvic diameter <15 mm during third trimester),
ultrasonography can be performed after they reach seven days of
age to see if the hydronephrosis is persistent postnatally . The
majority of cases with moderate hydronephrosis appear to resolve
by 18 months of age.
.This was illustrated by a prospective study of 282 infants (two
months of age) with renal pelvic diameters between 10 and 15
mm, which resolved (defined as renal pelvic diameter ≤ 5 mm on
two consecutive ultrasounds) in 94% of patients by 12 to 14
months of age. Of the 18 patients(6%) with persistent
hydronephrosis, 14 had UPJ obstruction and 4 had VUR.
Antibiotic prophylaxis
. Higher rates of urinary tract infections have been reported in
children with prenatally diagnosed hydronephrosis compare to the
general pediatric population .
. The risk of infection rises if there is an underlying urologic
abnormality, such as VUR or obstructive uropathy, and is greater
in girls compared to boys .
.As a result, in infants with severe hydronephrosis who are at greater
risk for an underlying urologic abnormality, antibiotic prophylaxis
(amoxicillin, 12 to 25 mg/kg PO daily) is started after delivery
until the diagnosis of VUR or obstructive uropathy is excluded.
.Antibiotic prophylaxis in children with mild or moderate
hydronephrosis confirmed postnatally has not been studied
prospectively. In one retrospective study of 1514 with mild
persistent hydronephrosis, the use of prophylactic antibiotics
reduced the risk of febrile UTI in patients who had VUR.
.Until further prospective studies are conducted, antibiotic
prophylaxis should be considered until a VCUG has been
performed and either the diagnosis of VUR has been made or
eliminated.
.Antiobiotic prophylaxis is not needed in infants with a normal
postnatal ultrasound.
There is very little evidence on which to base reliable
guidelines. As a rule, however, antibiotic prophylaxis is a
prudent precaution for all newborn infants with prenatally
detected uropathies, pending the outcome of postnatal
investigations (particularly VCU).
However, antibiotic prophylaxis may not be required for the
following, although it is still generally prescribed:
1. isolated renal dilatation with an AP diameter of 10 mm or less
2.unilateral multicystic dysplastic kidney with a normal
contralateral kidney and no evidence of contralateral or
ipsilateral ureteric dilatation
3.an ectopic but otherwise normal kidney.
Further evaluation
Persistent postnatal ultrasound findings
Infants with persistent hydronephrosis should have a VCUG to
detect vesicoureteral reflux (VUR).
.VUR accounts for approximately 9 percent of cases of
antenatal hydronephrosis, but it is a more common and
severe in infants with persistent postnatal hydronephrosis (13
to 30 percent)
.This was illustrated in a prospective study of 106 fetuses with
renal pelvic diameter ≥5 mm. Two postnatal ultrasounds were
performed at 5 to 7 days of age and during the third week of
life, and a VCUG at 6 to 8 weeks of life. The following
findings were noted:
.Of the 103 infants with complete data, 53 had normal postnatal
ultrasounds, defined as pelvic diameter ≤7 mm without evidence
of calyceal or ureteric dilatation, renal dysplasia, or other renal
anomalies. VUR was detected in only three infants with normal
postnatal ultrasounds, which was grade I in all three cases.
.Fifty infants had an abnormal postnatal ultrasound. Thirteen had
evidence of calyceal/ureteric dilatation but a normal renal pelvic
diameter (≤7 mm), of which one infant had grade IV VUR.
.Thirty-seven patients had persistent hydronephrosis (renal pelvic
diameter >7 mm), of which five infants had VUR (Grade IV and V
in three cases, and Grade II in two cases).
.Infants who have VUR demonstrated on VCUG should remain on
antibiotic prophylaxis until the therapeutic options can be
discussed with the family and care providers. Options include
observation, medical management including antibiotic
prophylaxis, or surgical correction.
If the VCUG is negative (no reflux):
• Infants with persistent postnatal severe hydronephrosis should have
diuretic renography (renal scan with Tc99mMAG3) to detect
possible obstruction.
.At this stage of evaluation, referral to center with expertise in
pediatric urologic care is warranted because the renal scan is an
invasive procedure requiring placement of an intravenous line and
bladder catheter, and surgical interventions may be required if the
kidney is obstructed.
.In general, diuretic renography can be performed after six weeks
of life because surgical intervention is rarely required (eg, severe
hydronephrosis without VUR).
.Infants with severe hydronephrosis without VUR are at risk for
developing UTIs .
.This was illustrated in two retrospective studies. In the first study of
105 infants diagnosed antenatally with severe hydronephrosis
without VUR who were not treated with prophylactic antibiotics,
36 percent of the infants developed an UTI by one year of age. In
the second study of 430 infants with persistent hydronephrosis
without VUR, the rates of UTIs were 40, 33, 14, and 4 percent in
patients with antenatal grade IV, III, II, and I hydronephrosis (as
defined by the Society for Fetal Urology classification in the first
year of life), respectively.
.Nevertheless, the use of antibiotic prophylaxis in patients with
prenatally diagnosed hydronephrosis that is subsequently
confirmed to be ureteropelvic junction (UPJ) type hydronephrosis
remains controversial. In general, antibiotic prophylaxis is given
until the time of the VCUG. If the VCUG does not show reflux in
general antibiotics are discontinued. However, in cases of the most
severe grade IV hydronephrosis or in patients with a solitary
kidney antibiotics are continued until surgical correction is
performed or a decrease in the severity of hydronephrosis is
detected by ultrasonography. It's prudent to remember that prior to
the era of prenatal sonography, UPJ obstruction typically
presented with urosepsis.
.In general, antibiotic prophylaxis is given until the time of the
VCUG. If the VCUG does not show reflux the antibiotics are
discontinued.
• Infants with postnatal hydronephrosis (renal pelvic diameter >7
mm) should have a repeat ultrasound when they reach three
months of age. Antibiotic prophylaxis is discontinued if the
hydronephrosis has not progressed. A meta-analysis of seven
studies, demonstrated that neonates with mild hydronephrosis
showed either improvement or stabilization. This finding appears
to be a benign condition .
.However, in a small number of patients, hydronephrosis may worsen
after initial improvement. In a retrospective review, four of 394
kidneys with hydronephrosis followed nonoperatively worsened
after initial spontaneous improvement on renal ultrasonography .
All four patients presented with clinical symptoms including
abdominal pain, gross hematuria, and vomiting at a mean age of
40 months of age (range 22 to 60 months) consistent with a
diagnosis of intermittent uretero pelvic junction obstruction
requiring pyeloplasty.
Normal postnatal ultrasound
Infants with a normal postnatal examination (defined as a renal
pelvic diameter ≤7 mm without any evidence of calyceal or
ureteric dilatation, or signs of renal dysplasia or anomalies) require
no further evaluation. This was supported in one study of patients
with antenatal hydronephrosis and normal postnatal ultrasounds
that demonstrated normal DMSA scans in 49 of the 103 children
available for evaluation at two-years of age . Renal ultrasound was
normal in three additional children whose families refused a
follow-up DMSA scan.