Dilatation of the fetal urinary tract is increasingly being recognized with wide-spread use of fetal
scanning, sophistication of ultrasound equipment and greater expertise. The pediatrician is often
faced with managing infants with asymptomatic hydronephrosis, which was detected in utero. In
most instances, mild to moderate dilatation of renal pelvis resolves after birth. However, all such
babies should be carefully investigated to exclude urinary tract obstruction and vesico-ureteric
reflux. There is considerable debate regarding optimal management of patients with antenatally
diagnosed hydronephrosis.
Antenatal Hydronephrosis
Antenatal hydronephrosis is the dilatation of the collecting system of the fetal kidney. Dilatation of
the ureter may be associated. It is estimated that fetal urinary tract dilatation is identified in 1% of
all pregnancies(1,4). In more than 50% cases, the antenatally detected dilatation is transient and
resolves sponta-neously(3,6). Antenatally detected dilatation, which persists after birth is labeled
as neo-natal hydronephrosis. Pelviureteric junction (PUJ) obstruction accounts for 50-60%
patients with neonatal hydronephrosis. Vesicoureteric reflux (VUR) is detected in 20-30% of such
cases(7). It sometimes may be difficult to differentiate multicystic dysplastic kidney from
hydronephrosis. Various causes of neonatal hydronephrosis are shown in Table 1.
Causes of Neonatal Hydronephrosis
Common
Pelviureteric junction obstruction
Vesicoureteric reflux
Vesicoureteric junction obstruction
Multicystic kidney
Rare
Posterior urethral valves
Obstructive and non-obstructive megaureter
Ureterocele
Neurogenic bladder
Prune-belly syndrome
Urethral atresia
Antenatal Evaluation
Fetal hydronephrosis of moderate degree can be detected as early as 15-18 weeks gestation by
ultrasonography. A maximum anteroposterior diameter of renal pelvis of more than 10 mm or the
ratio of antero-posterior diameter of renal pelvis to kidney of more than 0.5 after 30 weeks
gestation requires postnatal evaluation(8). The ultrasound study should be repeated every 6-8
weeks until delivery.
Oligohydramnios indicates severe urinary flow obstruction that may be seen in fetuses with
severe bilateral hydronephrosis and posterior urethral valves. A pediatric nephrologist or urologist
should be consulted for such cases.
Status of Fetal Intervention
The indications for performing bio-chemical investigations on fetal urine are limited. Similarly, the
criteria for fetal intervention are very few(9). Unilateral hydronephrosis of any severity does not
require fetal intervention or early termination of pregnancy. Fetuses with bilateral severe
hydronephrosis and significantly reduced amniotic fluid volume beyond 32 weeks of gestation
may be considered for premature delivery, if fetal lung maturity is established(9). Even in these
cases, it is not clear whether premature termination of pregnancy (to permit early postnatal
urinary decompression) is beneficial(8,9). This deci-sion should be judiciously weighed against
the risk of prematurity and involve a neonatologist, nephrologist and surgeon.
The parents should be counseled and reassured that as long as fetal growth is maintained, liquor
volume is normal and there are no other abnormalities, the pregnancy will be allowed to proceed
normally. They are given information about the proposed evaluation that is necessary after birth
of the baby.
Postnatal Evaluation
Majority of neonates with antenatally detected hydronephrosis are asymptomatic and would not
have been detected in the absence of prenatal ultrasonography. Rarely the newborn may have a
palpable abdominal mass, features of urinary tract obstruction or urosepsis. All infants detected to
have hydronephrosis in the antenatal period should be evaluated after birth. A detailed clinical
examination is done to exclude associated problems. Patients with an abdominal mass or where
the diagnosis of posterior urethral valves is suspected should be promptly evaluated. Unilateral
hydronephrosis in asymptomatic neonates usually does not require immediate intervention.
Parental anxiety should be allayed in such cases.
The presence of hydronephrosis is not synonymous with obstruction. Obstruction signifies
impairment of urinary flow, which if left untreated will cause progressive deterioration of renal
function. However, the diagnosis of obstruction is difficult to establish in the neonatal period.
Ultra-sonography and diuretic renography provide useful information but have their limitations.
Besides imaging, other tests include urinalysis, urine culture and blood levels of urea and
creatinine. Various investigations and stages at which they should be performed are shown in
Table III. A scheme for postnatal evaluation of antenatally detected hydro-nephrosis is given in
Fig. 1.
Ultrasonography
All babies with antenatally detected hydronephrosis should have an ultrasound examination
between 4–6 days of life. Hydronephrosis may be missed, due to physiological dehydration, if the
study is performed earlier. Ultrasonographic studies should be performed by those having a good
deal of experience in evaluation of kidneys and urinary tract in infants. The size and
anteroposterior diameter of renal pelvis, dilatation of ureters and associated renal anomalies are
evaluated. Further work up can be deferred for a few weeks unless bilateral disease or a serious
anomaly such as obstruction in the solitary kidney or urethral valves is suspected. If no dilatation
is seen, the ultrasound scan is repeated at 3-4 months of age.
Micturating Cystourethrography (MCU)
VUR (primary or associated with PUJ and vesicoureteric junction obstruction) may result in
hydronephrosis or hydrouretero- nephrosis(1,7,10). MCU should be performed to evaluate for
VUR and bladder outlet obstruction. The procedure should be done at 4–6 weeks postnatal age,
but earlier if bladder outlet obstruction is suspected. MCU is performed under antibiotic cover and
without sedation. Amoxicillin is administered orally in a dose of 50 mg/kg, 1 h before the procedure and 25 mg/kg 6 h later. Alternatively, gentamicin (2-3 mg/kg intramuscular) may be given 30
minutes before the MCU.
Nuclear Scintigraphy
Renal scintigraphy using 99mTc-diethy-lenetriamine pentaacetic acid (DTPA) or
mercaptotriglycine (MAG-3) with admi-nistration of frusemide (diuretic renography) is used to
estimate absolute and differential renal function and presence of PUJ obstruction. The diuretic
renogram is done at 4-6 weeks of age. Normally, the time required for clearance of 50% of the
accumulated radionuclide (t½) is less than 10 minutes, while t½ more than 20 minutes is
suggestive, but not diagnostic, of obstruction(4). Several factors such as the hydration status,
timing of diuretic administration, method of t½ calcula-tion, compliance of renal collecting system
and maturity of renal function can influence the results of renography. In a significant proportion
of infants, the procedure is equi-vocal and unable to differentiate obstructive from non-obstructive
hydronephrosis. The study should be done at centers with considerable experience in examining
infants and the results interpreted with caution.
Intravenous pyelography provides excellent anatomic details, but unsatisfactory
functional information. A diuretic renogram is superior to intravenous pyelogram due to
lower risk of contrast reactions and radiation exposure, and better quantitative assessment
of absolute and differential renal function. Patients with VUR are evaluated for renal
scarring with 99mTc-dimercaptosuccinic acid (DMSA) or glucoheptonate (GHA) renal
scan.
Postnatal Evaluation of Hydronephrosis
At birth
Clinical examination, assess urine stream
Asymptomatic unilateral hydronephrosis
0–2 weeks
Ultrasonography
Blood urea, creatinine; urine culture
4–6 weeks
Micturating cystourethrogram
DTPA scan (with diuretic renography)
Solitary kidney, suspected posterior urethral valves, bilateral hydronephrosis or presence of
symptoms
0–2 weeks
Ultrasonography
Blood urea, creatinine; urine culture
Micturating cystourethrogram
4–6 weeks
DTPA scan (with diuretic renography)
DMSA renal scan is performed in patients with vesicoureteric reflux
Fig. 1. Postnatal management of antenatally diagnosed hydronephrosis. Early evaluation is
necessary in neonates with solitary kidney, bilateral hydronephrosis or suspected bladder outlet
obstruction. MCU: micturating cystourethrogram; DMSA: dimercaptosuccinic acid scan: PUJ:
pelviureteric junction.
Management of Unilateral Hydronephrosis
Asymptomatic unilateral hydronephrosis is most often a benign condition. In majority of cases,
hydronephrosis due to PUJ obstruc-tion resolves spontaneously with passage of time(2,4,6).
Similarly, most cases of hydronephrosis and hydroureteronephrosis due to vesicoureteric junction
obstruction improve(11). Even in patients where hydro-nephrosis does not resolve, renal function
may not deteriorate. Approximately 10-20% patients with PUJ obstruction show progres-sion of
hydronephrosis or worsening renal functions(2,4,12). Kidneys with renal pelvic diameter more
than 20 mm are likely to show deterioration in renal function, which might require intervention(2).
Postnatally, it is difficult to distinugish whether hycdronephrosis is due to persistent obstruction
that will cause further renal dam-age, or whether a sequel of an antenatal event that has
resolved. Differentiating between obstructive and non-obstructive hydro-nephrosis requires
assessment of renal func-tion, over a period, with repeated radiological and radioisotope imaging.
Conservative Approach
The management of asymptomatic neo-natal hydronephrosis is essentially conserva-tive. This
approach is based on the observa-tion that majority of even severe neonatal hydronephrosis
resolve spontaneously and deterioration of renal function, if detected, can be reversed by prompt
surgery(3).
Initially, ultrasound examinations and radionuclide scans are performed once every 3-6 months.
Once renal morphology and function are stable, DTPA scan and ultra-sonography are performed
yearly. The size of hydronephrosis, cortical thickness and the degree of contralateral renal
hypertrophy (expected if function of the hydronephrotic kidney declines) are assessed on ultrasonography. Estimation of absolute and differential renal function is made on serial DTPA scans.
Obstruction has been reported to develop with time and worsening of renal function can occur as
late as 5 years during follow-up(13). Patients should be observed until hydronephrosis resolves or
the condition remains stable for a prolonged period.
Antibiotic prophylaxis
Prophylactic antibiotics should be administered, once daily, to all neonates with hydronephrosis.
Cephalexin (10-15 mg/kg/day) should be used for the initial 3 months, and cotrimoxazole (1-2
mg/kg/day) or nitro-furantoin (1 mg/kg/day) thereafter. In the absence of VUR, prophylactic
antibiotics should be discontinued after one year of age. Urine culture should be promptly
obtained if the patient has symptoms suggestive of urinary tract infection e.g., unexplained fever,
turbid or foul smelling urine, poor feeding and lethargy.
Surgical Correction
Infants with symptomatic hydronephrosis (e.g., recurrent urinary tract infection, palpable lump,
hematuria and hypertension) should undergo surgical correction. Surgery should also be
considered for kidneys, which show increasing pelvic dilatation or an obstructive pattern on
renography with greater than 10% decline in differential renal function on follow-up(2,3). The
indications for surgery are listed in Table IV. Decisions regarding surgery should jointly be taken
by pediatric surgeon and nephrologist.
Indications for Surgery in Neonatal Hydronephrosis
PUJ obstruction
At initial diagnosis
Presence of symptoms
Solitary kidney with hydronephrosis
Bilateral hydronephrosis
Differential renal function of obstructed kidney <30%
On follow-up
Increasing renal pelvic dilatation
>10% decline in differential renal function
Posterior urethral valve, ureterocele
Vesicoureteric reflux
Grade IV-V reflux persisting beyond infancy
New renal scars or recurrent urinary infections despite antibiotic prophylaxis
Occasionally patients with unilateral PUJ obstruction have poor (<10%) differential renal function.
In such instances, it is important to decide whether the affected kidney should be repaired or
removed. The decision is facilitated by placement of a nephrostomy tube, which serves as a
temporary diversion for 3-4 weeks. This is followed by reassessment of renal function on DTPA
renography. A pyeloplasty is performed if the renal function improves, whereas a nephrectomy is
considered if the differential function remains below 10%(5).
Bilateral Hydronephrosis
A MCU should be done in the first few weeks of life to rule out urethral obstruction or VUR. PUJ
obstruction may be bilateral in about 20% cases. Differential renal function is not very useful in
the management of these patients. In patients with bilateral PUJ obstruction, early pyeloplasty is
recom-mended on the side with greater dilatation or lesser function. Most infants require contralateral pyeloplasty and close follow-up.
Solitary Hydronephrotic Kidney
Early pyeloplasty, in the first few months of life, is recommended for neonates with significant
hydronephrosis (>20 mm pelvic diameter, obstructive pattern on renography). Those with mild
dilatation may be carefully followed up with ultrasound and isotope scans. Surgical intervention is
indicated in patients having symptoms, increasing hydronephrosis, or reduction in renal function.
Vesicoureteric Reflux
VUR is seen in 20-25% neonates with antenatally detected hydronephrosis, more commonly in
boys. Forty per cent neonates with VUR show features suggestive of renal scarring on DMSA
scan. Neonates with VUR should be managed on long-term antibiotic prophylaxis (while awaiting
spontaneous resolution of the reflux). The patients are kept on close follow-up for occurrence of
break-through urinary infections. An ultrasound examination, and radionuclide cystogram or MCU
should be repeated at 12-15 months. A DMSA renal scan, to detect fresh renal scarring, is
repeated in patients having breakthrough urinary infections. Occurrence of breakthrough urinary
tract infections, progressive renal scarring and persistence of grade IV-V VUR beyond infancy are
indica-tions for ureteral reimplantation(14,15).
Posterior Urethral Valves
This is the commonest cause of lower urinary tract obstruction in boys. A MCU is done as early
as possible to confirm the diagnosis. The initial treatment is correction of dehydration and
dyselectrolytemia, treat-ment of infection and prompt urine drainage by inserting a transurethral
or suprapubic catheter. Definitive therapy in the form of endoscopic valve ablation is possible in
many patients. Occasionally, a surgical vesico-stomy may be required (to drain the bladder). If
the child is severely ill and infected, drainage of the upper tract (ureterostomy or percutaneous
nephrostomy) may be neces-sary. The choice of the primary procedure depends on the clinical
and radiological features, and renal function(16). Patients with posterior urethral valves need
prolonged follow up since a significant proportion might develop features of renal insufficiency
later(17,18).
Ureterocele
Ureterocele is a cystic dilatation of the intravesical portion of the ureter, which can cause
obstruction either in a single system or the upper moiety of a duplex system. Endoscopic
puncture is usually successful in the neonatal period. Later, if needed, ureteric reimplantation,
bladder reconstruction or/and upper pole heminephrectomy may be required for the duplex
collecting system(19).
Conclusions
These recommendations represent the consensus view of the Indian Pediatric Nephrology Group.
They have been formulated on basis of best current practice, which is supported by studies
published in peer-reviewed journals and the experience of the Expert Group. They are intended
to provide pediatricians with broad guidelines for managing children with antenatally diagnosed
urinary tract dilatation.
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