Indian Pediatrics 2001; 38: 1244-1251
Consensus Statement on Management of Antenatally Detected Hydronephrosis
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.
An Expert Group Meeting of the Indian Pediatric Nephrology Group (Annexure 1) was held on 15 December 2000 at New Delhi to formulate guidelines for the management of antenatally detected hydronephrosis. The present document is based on their discussions and recommendations. Some of these guidelines may change with further experience and evidence. Detailed reviews on the topic are available elsewhere(1-5).
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.Table I__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
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). Various parameters that should be evaluated on a fetal ultrasound examination are shown in Table II. The ultrasound study should be repeated every 6-8 weeks until delivery.Table II__ Features Evaluated on Antenatal Ultrasonography
Hydronephrosis Renal pelvic anteroposterior diameter Caliectasis Ureteral dilatation Renal echogenicity Contralateral kidney: size, dilatation Bladder size, thickness Posterior urethral dilatation Urinary flow Amniotic fluid volume
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.
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.
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 proce-dure and 25 mg/kg 6 h later. Alternatively, gentamicin (2-3 mg/kg intramuscular) may be given 30 minutes before the MCU.
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.
Table III__Postnatal Evaluation of Hydronephrosis
DMSA renal scan is performed in patients with vesicoureteric reflux
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.
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 ultra-sonography. 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.
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.
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.Table IV__ 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).
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 contra-lateral 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.
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 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).
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.