Postnatal management of antenatal hydronephrosis 2

APPROACH —
The risk of renal and urinary tract abnormality increases with the severity of hydronephrosis, persistence of hydronephrosis into the third trimester, bilateral involvement, and the presence of oligohydramnios.
Our management approach of infants with antenatal hydronephrosis is based upon these two predicative factors.
· --Bilateral involvement
· Severe hydronephrosis — Fetuses with renal pelvic diameter >15 mm during the third trimester are at the greatest risk for significant renal disease.
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 ( show figure 1). Bilateral hydronephrosis suggests an obstructive process at the level or distal to the bladder such as ureterocoele 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.
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 week of life) to ensure volume repletion ( show figure 2). Antibiotic prophylaxis ( amoxicillin, 12 to 25 mg/kg PO daily) is started after delivery until the diagnosis of VUR or obstructive uropathy is excluded.

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 ( show figure 2). Antibiotic prophylaxis in children with mild or moderate hydronephrosis confirmed postnatally has not been studied prospectively but a higher rate of urinary tract infections has been reported in children with prenatally diagnosed hydronephrosis [ 10]. Antibiotic prophylaxis should therefore be considered until the VCUG has been performed and either the diagnosis of VUR has made or eliminated.
Further evaluation
Persistent postnatal hydronephrosis — Infants with persistent hydronephrosis should have a VCUG to detect vesicoureteral reflux (VUR) ( show figure 1 and show figure 2). VUR accounts for approximately 9 percent of cases of antenatal hydronephrosis [ 3], but it is a more common in infants with persistent postnatal hydronephrosis (20 to 30 percent). Infants who have VUR demonstrated on VCUG should remain on antibiotic prophylaxis until the reflux resolves.
If the VCUG is negative (no reflux), ( show figure 1 and show figure 2):
· 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). In infants with severe hydronephrosis without VUR, antibiotic prophylaxis is continued until surgical correction is performed or a decrease in the severity of hydronephrosis is detected by ultrasonography.
· Infants with no, mild, or moderate postnatal hydronephrosis 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 [ 11].
SUMMARY AND RECOMMENDATIONS
· Fetal hydronephrosis (fetal renal pelvic dilatation) is a common, readily diagnosed finding on antenatal ultrasonography and can be as early as the 12th week of gestation.
· Although antenatal hydronephrosis is most often transient or clinically insignificant, urinary tract obstruction or vesicoureteral reflux (VUR) are important causes that should be diagnosed soon after birth because they can result in renal impairment or cause further renal damage.
· The risk of renal and urinary tract abnormality increases with the severity of hydronephrosis, persistence of hydronephrosis into the third trimester, bilateral involvement, and the presence of oligohydramnios.
· Postnatal management is dependent upon the presence of predicative factors (bilateral involvement and severity of hydronephrosis), to identify all infants with significant disease but limit unnecessary radiographic studies and minimize parental distress in those without significant.
· In infants with severe antenatal hydronephrosis, we suggest antibiotic prophylaxis .In our practice, we use amoxicillin, 12 to 25 mg/kg as a single oral daily dose. Antibiotic prophylaxis is discontinued when VUR and significant obstructive uropathy are ruled out as causes of antenatal hydronephrosis.
· We suggest that all infants with bilateral antenatal hydronephrosis be evaluated initially by ultrasonography on the first postnatal day. If the postnatal ultrasound demonstrates persistent hydronephrosis, a voiding cystourethogram (VCUG) should be performed.
· In infants with severe unilateral hydronephrosis, we suggest that ultrasonography be performed after the infant returns to birth weight after 48 hours of age and within the first week of life
· In infants with mild to moderate unilateral hydronephrosis, we suggest that ultrasonography be performed after seven days of age
· Further testing is dependent upon whether there is persistent postnatal hydronephrosis.


dr Salim alatwane
ped. nephrologist