A newborn with a urinary tract anomaly:
What role for the general pediatrician?

By Beth A. Vogt, MD

Being familiar with urinary tract anomalies identified on fetal sonography enables you to take steps to prevent problems in the newborn, facilitate early evaluation by a subspecialist, improve the coordination of surgical and medical care, and counsel the family appropriately.

In the past, congenital anomalies of the urinary tract often went undetected until the infant developed a palpable abdominal mass, febrile urinary tract infection, failure to thrive, or signs of renal insufficiency. Today, it is not uncommon for a parent or obstetrician to notify the pediatrician of a urinary tract anomaly before the infant's birth or in the newborn nursery. In fact, as many as one in 100 prenatal sonograms identifies an anomaly of the fetal urinary tract.¹ Parents may tell the pediatrician that there was "fluid on the kidneys," "not enough amniotic fluid," or "cysts on the kidneys," or that the doctors "couldn't find one of the kidneys." The obstetrician may report hydronephrosis, oligohydramnios, or cystic abnormalities of the kidneys.

Conditions discussed in this article

Hydronephrosis
Physiologic hydronephrosis
Anomalous ureteropelvic junction obstruction
Ureterovesical junction obstruction
Vesicoureteral reflux
Posterior urethral valves
Eagle-Barrett syndrome (prune-belly syndrome)
Renal agenesis
Renal dysplasia
Multicystic-dysplastic kidney
Polycystic kidney disease

You may find yourself fielding questions about these conditions from anxious parents and guiding the initial care of infants with urinary tract abnormalities identified by prenatal ultrasonography (US). To help you do so, this article reviews some of the more common urinary tract anomalies, using case scenarios to illustrate situations you might encounter in your practice, and offers logical approaches to the management of these conditions in newborns.

Prenatal assessment of the urinary tract

We now have access to much more information about the status of the fetal urinary tract than was ever available. As early as 12 to 14 weeks' gestation, prenatal US can detect conditions such as hydronephrosis (dilatation of the upper urinary tract) and hydroureter (dilatation of the ureter). At 18 weeks, US can offer specific information about the kidneys, including size, echogenicity, and the presence or absence of cysts. Beyond 18 to 20 weeks' gestation, the bladder size, shape, and volume and the amniotic fluid volume offer indirect information about fetal renal function.

Because of progressive renal growth and the increase in fetal urine output throughout pregnancy, US is more likely to show a significant abnormality during the third trimester than during the second trimester. Therefore, a normal 20-week screening sonogram does not necessarily rule out urinary tract pathology. Detection of oligohydramnios, increased renal echogenicity, small or enlarged kidneys, bilateral renal cysts, or moderate to severe bilateral hydronephrosis at any time during gestation suggests significant urinary tract pathology and may predict poor long-term renal function (Table 1).

TABLE 1
Findings on the prenatal sonogram suggestive of a poor outcome

Hydronephrosis

Dilatation of the upper urinary tract accounts for 50% of prenatally detected urologic anomalies. A number of conditions may cause fetal hydronephrosis (Table 2). Hydronephrosis may be graded from 1 to 4 in severity, according to a grading system created by the Society for Fetal Urology (SFU).² Mild hydronephrosis is much more common than severe hydronephrosis, and carries an excellent prognosis, whereas severe hydronephrosis suggests more significant urinary tract pathology and a poorer outcome.

TABLE 2
What is the etiology of hydronephrosis detected prenatally?

Prenatal management. A fetus with mild or moderate hydronephrosis is generally observed with serial prenatal sonograms. A fetus with severe bilateral hydronephrosis, such as one with posterior urethral valves (PUV) or Eagle-Barrett syndrome (prune- belly syndrome), may be considered for antenatal surgical treatment. Options include percutaneous vesicoamniotic shunt placement, bladder aspiration, amnioinfusion, and drainage of a severely distended kidney.³ The goals of such procedures include, first, correction of oligohydramnios, which may decrease the risk of pulmonary hypoplasia, and, second, improvement in urinary tract drainage, which may decrease the risk of further renal damage.

Antenatal surgical treatment for severe bilateral hydronephrosis remains controversial because no large, well-designed studies have been performed to confirm its efficacy. There have, however, been small studies that suggest that intrauterine surgical intervention may help fetuses that have the most severe forms of obstructive uropathy.⁴ Antenatal surgical intervention does involve significant risks, including preterm labor, hemorrhage, and chorioamnionitis. The consensus is that intrauterine intervention should be considered only if:

• persistent or progressive oligohydramnios develops in a fetus with a normal karyotype

• no other life-threatening anomalies are evident

• fetal immaturity precludes delivery.

Delivery of the infant with severe bilateral hydronephrosis should be arranged at a tertiary care center to avoid delays in postnatal treatment. The family should be referred for prenatal consultation with a pediatric nephrologist and urologist. Consultation with a neonatologist to discuss neonatal intensive care unit (NICU) procedures and ventilatory management may also be helpful.

Postnatal management. After delivery, consensus practice is to administer prophylactic antibiotics to all newborns with moderate or severe hydronephrosis. The most commonly used antibiotic for prophylaxis in infants under 2 months of age is amoxicillin, at a dosage of 20 mg/kg/d in two divided doses. The routine administration of prophylactic antibiotics in an infant with only mild hydronephrosis is controversial.⁵ A bladder catheter should be placed in infants with severe bilateral hydronephrosis, such as those with suspected posterior urethral valves or Eagle-Barrett syndrome. Bladder drainage is not required in infants with unilateral hydronephrosis or mild to moderate bilateral hydronephrosis unless there is evidence of bladder dysfunction.

An infant with moderate or severe hydronephrosis on prenatal US should have renal US performed within the first few days of life. A repeat sonogram is mandatory within several weeks because the degree of hydronephrosis may be significantly underestimated as a result of the relatively low urine output of the newborn during the first 72 hours of life. In an infant with only mild hydronephrosis on prenatal US, the initial postnatal sonogram should be delayed until 2 weeks of age.

Additional imaging evaluation to determine the precise cause of hydronephrosis should be arranged by a pediatric urologist. A contrast voiding cystourethrogram (VCUG) should be performed to determine whether vesicoureteral reflux (VUR) is present and to delineate the anatomy of the bladder and urethra. A diuretic-enhanced radionuclide renal scan with mercaptoacetyl triglycine (MAG3) may be considered to differentiate true obstruction from pseudo-obstruction. Surgical intervention may be required in an infant or child with true urinary tract obstruction, such as ureteropelvic junction obstruction (UPJO), ureterovesical junction obstruction (UVJO), or PUV.

Physiologic hydronephrosis

You are seeing a 2-week-old girl for an initial clinic visit and learn that a prenatal sonogram revealed mild hydronephrosis. A follow-up sonogram ordered by the discharging pediatrician was performed immediately before today's visit and is read as normal. Is there need for further follow-up?

In as many as 88% of cases of prenatally detected mild hydronephrosis, the problem resolves spontaneously and is not associated with an anatomic abnormality of the urinary tract.⁶ This condition, termed physiologic hydronephrosis, may be caused by a delay in the maturation of the ureter, which leads to transient obstruction of urinary flow in utero. In addition, a relatively high fetal urine flow rate may contribute to the phenomenon.

When mild hydronephrosis persists postnatally, the infant should be followed with serial US to watch for resolution of the condition. Many clinicians administer a prophylactic antibiotic until a VCUG rules out vesicoureteral reflux, although some believe this practice unnecessary when hydronephrosis is mild.⁵

Anomalous ureteropelvic junction obstruction

Your patient is a newborn boy who was born at 39 weeks' gestation to a healthy 34-year-old woman. On reviewing his chart, you note that a routine prenatal sonogram at 20 weeks' gestation revealed "moderate to severe hydronephrosis of the left kidney without dilatation of the left ureter"; the right kidney and bladder appeared normal, amniotic fluid volume was adequate, and no other congenital anomalies were noted. The infant's physical examination is entirely normal. What interventions are indicated?

Anomalous UPJO is the most common cause of significant congenital hydronephrosis, accounting for 50% of cases of prenatally detected hydronephrosis. Anomalous UPJO refers to a spectrum of abnormalities, ranging from fetal folds of the upper ureter that cause urinary stasis to a true UPJO related to a fibrotic stenosis of the ureteropelvic junction.⁷ This condition has a male predominance, is more common on the left side, and may be associated with other congenital anomalies, syndromes, or genitourinary malformations. Ten percent to 15% of patients with UPJO have vesicoureteral reflux; 5% of cases of UPJO are bilateral.

In an infant with suspected UPJO, like the newborn male in the vignette, a diuretic-enhanced radionuclide scan should be performed at 6 weeks of age to determine whether there is true obstruction. An infant with nonobstructive hydronephrosis may be followed conservatively. Many clinicians advocate antibiotic prophylaxis to prevent urinary tract infection, but this practice remains somewhat controversial in cases of anomalous UPJO without reflux. If there is no contraindication to circumcision (such as hypospadias, chordee, webbed penis, or megalourethra), consensus practice is to circumcise boys with anomalous UPJO to reduce the risk of urinary tract infection. An infant with true obstruction of the ureteropelvic junction may be considered for surgical repair, particularly if renal function is declining, hydronephrosis is increasing in severity, or disease is bilateral.

Ureterovesical junction obstruction

An obstetrician calls to inform you of the delivery of a term male infant whose prenatal sonogram showed left-sided hydronephrosis and hydroureter. The right-sided collecting system and bladder appeared normal and there was no oligohydramnios. What do you do?

UVJO is the second most common cause of congenital hydronephrosis. It is characterized by hydronephrosis with associated dilatation of the ureter. This disorder may be related to maldevelopment of the distal ureteral muscle, the presence of a ureterocele (cystic dilatation of the distal end of the ureter), or an ectopic ureter (ureter which inserts into an abnormal location within the urinary tract). Diagnosis is confirmed by radionuclide scan and VCUG, which usually shows no reflux. UVJO is usually not associated with other congenital malformations.

In an infant with suspected UVJO, like the newborn male in the vignette, a renal US should be ordered to confirm the hydronephrosis and evaluate for associated renal dysplasia. A VCUG should be performed to rule out vesicoureteral reflux. Many clinicians advocate antibiotic prophylaxis to prevent urinary tract infection, although this practice remains somewhat controversial in cases of UVJO without associated reflux. Spontaneous improvement is common, and surgical excision of the abnormal segment with ureteral reimplantation is reserved for children with deteriorating renal function, worsening urinary tract dilatation, or recurrent urinary tract infection. Children with UVJO related to ureteroceles and ectopic ureters must undergo corrective urologic surgery as well.

Vesicoureteral reflux

The mother of a healthy newborn girl is concerned about an abnormality noted on her routine 20-week prenatal sonogram: mild bilateral hydronephrosis. The mother is especially concerned because her 3-year-old daughter has a history of recurrent urinary tract infection and was recently given a diagnosis of vesicoureteral reflux. The child appears healthy; what is your next step?

Some infants with VUR are identified by a finding of hydronephrosis on prenatal US. VUR, which occurs in approximately 1% of children, is defined as retrograde propulsion of urine from the bladder to the kidneys. It results from incomplete development of the ureterovesical junction. VUR has a genetic component: Its incidence is 35% in first-degree relatives.⁸

In the infant in the case scenario, a renal US should be performed at 2 weeks of age to evaluate for persistence of hydronephrosis. All infants with persistent hydronephrosis should undergo a VCUG to rule out VUR. Some clinicians recommend that a VCUG also be performed in infants in whom hydronephrosis resolves, as VUR cannot be excluded by a normal US. A screening VCUG should be considered in infants who have first-degree relatives with VUR, such as the girl in the vignette, regardless of the prenatal US findings.⁹ Primary VUR tends to resolve over time as the intravesicular segment of the ureter elongates with growth. The greatest rate of spontaneous resolution occurs with the lower grades of reflux.

Daily oral antibiotic prophylaxis is important to prevent urinary tract infection and should be given until a follow-up VCUG, performed every 12 to 18 months, shows resolution of VUR. Surgical repair is reserved for children who have breakthrough urinary tract infections or high-grade reflux. To reduce the risk of urinary tract infection, circumcision should be performed in boys if there is no contraindication. Long-term complications of VUR include hypertension, renal scarring, and chronic renal failure.¹⁰

Posterior urethral valves

You are asked to evaluate a newborn boy born at 36 weeks' gestation who has developed mild respiratory distress within the first 24 hours of life. Review of the record reveals that the infant had severe bilateral hydronephrosis and ureteral dilatation initially detected on a prenatal sonogram at 18 weeks' gestation. The bladder wall was thickened and trabeculated and there was mild oligohydramnios throughout the pregnancy. Antenatal intervention was offered but declined by the family. The infant is in mild respiratory distress and has bilateral abdominal masses as well as a palpable bladder. The remainder of the examination, including assessment of the genitalia, is normal. What interventions should be initiated?

An infant with severe bilateral hydronephrosis, hydroureters, and a trabeculated bladder on prenatal US is presumed to have congenital obstruction of the bladder outlet. Posterior urethral valves—remnants of a congenital membrane that completely or partially obstruct the posterior urethra—are the most common cause of bladder outlet obstruction, with an incidence of one in every 5,000 to one in every 8,000 male births.¹¹

Prenatal US may show hydronephrosis, dilated ureters, thickened trabeculated bladder, a dilated proximal urethra, and oligohydramnios (Figure 1). Postnatal presentation may include a palpable, distended bladder, poor urinary stream, and signs and symptoms of renal and pulmonary insufficiency. VCUG shows a dilated posterior urethra, which is diagnostic for posterior urethral valves (Figure 2). VUR is seen in 50% of patients with PUV.

Treatment of this newborn boy, like that of other infants with PUV, is best accomplished in a NICU with the care of both a pediatric nephrologist and a pediatric urologist and where care for the child's respiratory distress can be provided. A bladder catheter should be placed as soon as possible to bypass the obstruction caused by the valves and to secure adequate drainage of the urinary tract. Ultrasonography should be performed to assess the urinary tract, and serial serum creatinine and electrolyte levels should be measured to follow renal function. Surgical options include primary ablation of the valves, cutaneous vesicostomy, or, rarely, upper-tract diversion. Circumcision to reduce the risk of urinary tract infection should be performed if there is no contraindication, and long-term antibiotic prophylaxis should be administered.

Outcome depends on the degree of associated renal dysplasia. Some infants with PUV do not survive the neonatal period because of severe pulmonary hypoplasia. At least 30% of boys with PUV who are first seen in infancy develop end-stage renal disease in childhood or adolescence.¹²

Eagle-Barrett syndrome

A mother who had limited prenatal care delivers a 2,500 g male infant who has an obvious abnormality of the abdominal wall. His abdomen is flaccid, distended, and wrinkled. In addition, you note bilateral cryptorchidism. As the delivery room staff looks at the infant, the mother asks you, "What is wrong with my baby?" What do you say?

A triad of findings—deficiency of abdominal wall musculature, dilated nonobstructed urinary tract, and bilateral cryptorchidism— characterizes Eagle-Barrett syndrome (EBS), also known as prune-belly syndrome (Figure 3). The estimated incidence is one in every 35,000 to 50,000 live births, with more than 95% of cases occurring in boys.¹³ The most common urinary tract abnormalities in infants with EBS are renal dysplasia, VUR, and a large-capacity, poorly contractile bladder. Cardiac, pulmonary, gastrointestinal, and orthopedic anomalies occur in a significant percentage of EBS patients. Two theories of pathogenesis are in utero urinary tract obstruction and a specific mesodermal injury between the fourth and tenth weeks of gestation.¹³

Infants with EBS are best served by initial care in a NICU, under the guidance of a pediatric nephrologist and pediatric urologist. Treatment involves optimization of urinary tract drainage, management of renal insufficiency, and antibiotic prophylaxis. Management later in childhood may include orchiopexy, reconstruction of the abdominal wall, and surgical repair of reflux. Some infants with EBS do not survive the neonatal period because of severe pulmonary hypoplasia. At least 30% of boys with EBS develop end-stage renal disease in childhood or adolescence, requiring dialysis or renal transplantation.

Renal agenesis

A 3,200 g boy was delivered at term by spontaneous vaginal delivery. The obstetrician notifies you that a routine prenatal sonogram failed to show a right kidney. The left kidney appeared normal, no other anomalies were noted, and there was no oligohydramnios. Your initial physical examination is normal and the baby is now ready for discharge. How do you proceed?

Unilateral renal agenesis—congenital absence of the kidney—is found in one in every 500 to one in every 3,200 people.¹⁴ Renal agenesis results when the ureteric bud fails to induce proper differentiation of the metanephric blastema, an event that may be related to both a genetic predisposition and environmental factors. Although renal agenesis may occur in otherwise healthy infants, 25% to 40% of infants with renal agenesis have associated conditions such as congenital heart disease, genital anomalies, VACTERL (vertebral, anal, cardiac, tracheal, esophageal, renal, limb) association, caudal regression syndrome, branchio-oto-renal syndrome, and multiple chromosomal defects.¹⁴ Therefore, any child with suspected renal agenesis should receive a careful physical examination to identify other anomalies.

Twenty percent of infants with unilateral renal agenesis have an abnormality of the contralateral urinary tract, such as VUR, UPJO, renal dysplasia, or ureterocele. An infant with renal agenesis should have a renal sonogram before discharge to ensure that the contralateral kidney is not hypoplastic, dysplastic, or obstructed. If the contralateral kidney appears normal, arrange outpatient follow-up with a pediatric nephrologist to monitor for adequate growth of the single kidney. If the contralateral kidney appears abnormal, measure serum electrolyte, BUN, and creatinine levels and consult a nephrologist before discharge. Antibiotic prophylaxis should be administered until a VCUG rules out vesicoureteral reflux.

Renal dysplasia

A 2,100 g girl was delivered at 35 weeks by cesarean section. Mild oligohydramnios and bilaterally small echogenic kidneys had been noted in the third trimester by US. Apgar score was 8 at 1 minute and 9 at 5 minutes. Physical examination was normal, including the absence of abdominal masses. Over the first three days of life, she fed poorly and became listless. Laboratory evaluation revealed metabolic acidosis and a serum creatinine level of 2.5 mg/dL. Postnatal renal US confirmed the presence of small, hyperechoic kidneys with rare cortical cysts. What is the prognosis for this infant?

Renal dysplasia is defined as abnormal fetal renal development leading to replacement of the renal parenchyma by cartilage and disorganized epithelial structures. This congenital malformation may be caused by mutations in developmental genes, altered interaction of the ureteric bud with extracellular matrix, abnormalities of renal growth factors, or urinary tract obstruction.¹⁵ Although otherwise healthy infants may have renal dysplasia, infants with obstructive uropathy, EBS, VACTERL association, branchio-oto-renal syndrome, CHARGE syndrome (coloboma of the iris, heart defects, atresia choanae, growth and mental retardation, genitourinary defects, and ear anomalies), and trisomies 13, 18, and 21 have an increased incidence of renal dysplasia. Therefore, any child with suspected renal dysplasia should have a careful physical examination to check for other anomalies.

Renal US should be performed within the first few days of life to confirm the diagnosis of dysplasia and to look for other urinary tract anomalies. A prophylactic antibiotic should be administered until a VCUG can be arranged to rule out VUR or urinary tract obstruction. In all infants with suspected bilateral renal dysplasia, obtain serial serum electrolyte, BUN, and creatinine level measurements, and consult a nephrologist. Such infants may exhibit signs of renal insufficiency as early as the first few days of life. Concentrating and acidification defects may also be present. In contrast, hematuria, proteinuria, hypertension, and oliguria are unusual findings.

Infants with bilateral renal dysplasia, such as the infant in the case scenario, generally develop progressive renal insufficiency during childhood and adolescence. Management includes medications to supplement or replace the functions of the failing kidneys, dietary manipulation (for example, a low phosphorus, low potassium, high or low volume, or high or low salt diet), supplemental nasogastric feedings, and, ultimately, dialysis or kidney transplantation.

Multicystic-dysplastic kidney

You are seeing a full-term newborn girl for her discharge physical. Her mother recalls that a routine prenatal sonogram performed at 20 weeks' gestation showed "large cysts on one of the kidneys." You track down the prenatal sonogram report, which describes multiple cystic masses within the right kidney. The left kidney appeared normal, though there was mild dilatation of the collecting system. The bladder was normal, as was amniotic fluid volume. No other anomalies were detected by US. Your physical examination reveals a healthy female with a palpable right-sided abdominal mass. What should you do?

Multicystic-dysplastic kidney (MCDK) is the most common cause of an abdominal mass in a newborn. Most MCDKs are now detected incidentally by prenatal US.¹⁶ The presence of multiple cystic masses in one kidney on a prenatal sonogram is highly suggestive of an MCDK (Figure 4). It is important to note that perinatologists often erroneously describe this finding as a "polycystic kidney." An MCDK, a congenital malformation, is an entirely different condition than polycystic kidney disease (discussed later), which is an inherited renal disease with a totally different prognosis.

An MCDK, estimated to occur in one in every 4,300 live births, represents the most severe form of renal dysplasia.¹⁷ The affected kidney is nonfunctional. It resembles a grape-like cluster of cysts devoid of any normal renal architecture (Figure 5). Although an MCDK usually occurs as a sporadic event, it may be associated with VACTERL association, branchio-oto-renal syndrome, Williams syndrome, Beckwith-Weidemann syndrome, and trisomy 18 and 49,XXXXX syndrome. An infant with a suspected MCDK should have a thorough physical examination to identify any other congenital anomalies.

Because contralateral urinary tract abnormalities are present in approximately 20% of patients with an MCDK, study the contralateral kidney carefully by US before discharging the infant to ensure that it is not hypoplastic, dysplastic, or obstructed. If the contralateral kidney appears normal, arrange for subspecialty consultation with a pediatric urologist for ongoing follow-up. If the contralateral kidney appears abnormal, measure serial serum electrolytes, BUN, and creatinine levels and consult a pediatric nephrologist before discharge. Prescribe prophylactic antibiotics for the infant until a VCUG can be arranged to rule out vesicoureteral reflux, which is seen in 15% of individuals with an MCDK.¹⁸

The majority of MCDKs undergo spontaneous involution over time. Compensatory hypertrophy of the contralateral kidney occurs in 93% of patients with a unilateral MCDK.¹⁹ The single healthy kidney usually maintains normal function; with conservative management, the long-term outcome is excellent.²⁰ In view of the small but real risk of hypertension and malignant change, however, some clinicians offer surgical removal of an MCDK in infancy.²¹

Polycystic kidney disease

The mother of a child already in your practice calls you for advice immediately following her routine 18-week prenatal sonogram. The technician told her that the baby's kidneys appear very bright and much larger than normal and that the amniotic fluid volume was a little low. The bladder appeared to be normal and there was no hydronephrosis. Because her obstetrician is out of town for the week, she asks you to tell her what these findings mean.

Both autosomal recessive polycystic kidney disease (ARPKD) and autosomal dominant polycystic kidney disease (ADPKD) can be detected on prenatal US. ARPKD is an uncommon disorder, with an incidence of one case in every 30,000 to 50,000 people, and most cases are first seen in infancy. Prenatal US may show oligohydramnios and bilaterally large, echogenic kidneys. Characteristic neonatal findings include palpable abdominal masses, severe hypertension, pulmonary hypoplasia, congenital hepatic fibrosis, and renal insufficiency. Primary management in the neonatal period includes control of hypertension, management of renal insufficiency, and ventilatory support. Progression to end-stage renal failure is inevitable despite supportive care, and ultimately all patients require dialysis or renal transplantation.

ADPKD is a much more common condition than ARPKD, with an incidence of one in every 200 to one in every 1,000 people, representing the most common inherited renal disease.²² The PKD1 gene (on chromosome 16) and PKD2 gene (on chromosome 2) have been identified, and mutations in these genes may alter a multimeric protein complex that has an important regulatory role in kidney development, triggering ADPKD.²² Prenatal US may show unilateral or bilateral cortical cysts. Most people with ADPKD remain asymptomatic throughout childhood. In the third to fifth decades of life, they may develop back pain, hypertension, kidney stones, and renal insufficiency. In rare cases, neonatal ADPKD is associated with a clinically symptomatic presentation with advanced renal failure and severe hypertension.

Families who have a prenatal sonogram suspicious for ARPKD or ADPKD should be referred for prenatal consultation with a pediatric nephrologist and a neonatologist. A detailed family history may help distinguish between ARPKD and ADPKD and provide prognostic information for the family. Although there is no effective prenatal intervention, early preparation and education of the family as well as mobilization of resources are critically important in the treatment of children with PKD.

Management approaches to urinary tract anomalies

Given that as many as 80% of infants with an antenatally detected urinary tract anomaly are asymptomatic at birth,²³ the widespread use of prenatal US offers pediatricians a great opportunity to stave off preventable morbidity and mortality in these at-risk infants. At least one study has demonstrated the favorable impact of prenatal identification of severe urinary tract anomalies—including improved growth, fewer urinary tract infections, and a lower incidence of reduced renal function.²⁴

A general approach to management of infants with any of the more common conditions you may encounter is outlined in Table 3. By taking that approach, the opportunity for you to have an immediately meaningful impact on these children's health is significant:

• You may be able to make a prenatal referral for the infant with a urinary tract anomaly (Table 4), allowing the family to gain important information and adjust to the possibility of a congenital anomaly.

• You may be able to initiate antibiotic prophylaxis in a newborn with hydronephrosis, possibly preventing an episode of pyelonephritis and its potential long-term complications.

• You may be able to make the timely telephone call to a subspecialist, which can allow early evaluation of the infant and possibly avoid rehospitalization.

• Last, your knowledge of congenital urinary tract anomalies can lead to improved coordination of surgical and medical interventions and more effective care. Excellent communication between the obstetrician, parents, and primary pediatrician is clearly critical in achieving this goal.

TABLE 4
When to order a prenatal consultation

REFERENCES

1. Roth J, Diamond D: Prenatal hydronephrosis. Curr Opin Pediatr 2001;13:138

2. Maizels M, Reisman M, Flom L, et al: Grading nephroureteral dilatation detected in the first year of life: Correlation with obstruction. J Urol 1992;148:609

3. Mouriquand P, Troisfontaines E, Wilcox D: Antenatal and perinatal uro-nephrology: Current questions and dilemmas. Pediatr Nephrol 1999;13:938

4. Freedman A, Johnson M, Smith C, et al: Long-term outcome in children after antenatal intervention for obstructive uropathies. Lancet 1999;354:374

5. Misra D, Kempley S, Hird M: Are patients with antenatally diagnosed hydronephrosis being over-investigated and overtreated? Eur J Pediatr Surg 1999;9:303

6. Sairam S, Al-Habib A, Sasson S, et al: Natural history of fetal hydronephrosis diagnosed on mid-trimester ultrasound. Ultrasound Obstet Gynecol 2001;17:191

7. Park J, Bloom D: The pathophysiology of UPJ obstruction: Current concepts. Urol Clin N Am 1998;25:161

8. Greenfield S, Wan J: Vesicoureteral reflux: Practical aspects of evaluation and management. Pediatr Nephrol 1996;10:789

9. Scott J, Swallow V, Coulthard M, et al: Screening of newborn babies for familial ureteric reflux. Lancet 1997;350:396

10. Smellie J, Prescod N, Shaw P, et al: Childhood reflux and urinary infection: A follow-up of 10–41 years in 226 adults. Pediatr Nephrol 1998;12:727

11. Dinneen M, Duffy P: Posterior urethral valves. British J Urol 1996;78:275

12. Parkhouse H, Barratt T, Dillon M, et al: Long-term outcome of boys with posterior urethral valves. Br J Urol 1988;62:59

13. Sutherland R, Mevorach R, Kogan B: The prune-belly syndrome: Current insights. Pediatr Nephrol 1995; 9:770

14. Robson W, Leung A, Rogers R: Unilateral renal agenesis. Adv Peds 1995;42:575

15. Woolf A, Winyard P: Advances in the cell biology and genetics of human kidney malformations. J Am Soc Nephrol 1998;9:1114

16. Wacksman J, Phipps L: Report of the Multicystic Kidney Registry: Preliminary findings. J Urol 1993; 150:1870

17. Robson W, Leung A, Thomason M: Multicystic dysplasia of the kidney. Clin Pediatr 1995;34:32

18. Selzman A, Elder J: Contralateral vesicoureteral reflux in children with a multicystic kidney. J Urol 1995; 153:1252

19. John U, Rudnik-Schoneborn S, Zerres K, et al: Kidney growth and renal function in unilateral multicystic dysplastic kidney disease. Pediatr Nephrol 1998;12:567

20. Strife J, Souza A, Kirks D, et al: Multicystic dysplastic kidney in children: US follow-up. Radiology 1993; 186:785

21. Webb N, Lewis M, Bruce J, et al: Unilateral multicystic dysplastic kidney: The case for nephrectomy. Arch Dis Child 1997;76:31

22. Murcia N, Woychik R, Avner E: The molecular biology of polycystic kidney disease. Pediatr Nephrol 1998; 12:721

23. Estes J, Harrison M: Fetal obstructive uropathy. Seminars in Pediatric Surgery 1993;2:129

24. Murphy J, Kaplan G, Packer M, et al: Prenatal diagnosis of severe urinary tract anomalies improves renal function and growth. Child Nephrol Urol 1988;9:290

DR. VOGT is associate professor of pediatrics, division of pediatric nephrology, Rainbow Babies and Children's Hospital, Cleveland, Ohio.

Beth Vogt. A newborn with a urinary tract anomaly: What role for the general pediatrician?

Contemporary Pediatrics

October 2002;19:131.