Prenatally diagnosed hydronephrosis and infants/evaluating and managing

Question 1

What is the most common abnormality found on routine screening at the prenatal ultrasound?

Answer 1

Genitourinary and kidney abnormalities.

Question 2

What is the most common genitourinary abnormality identified on prenatal ultrasounds?

Answer 2

Hydronephrosis or dilation of the proximal urinary collecting system occurs in up to 0.6% of all prenatal ultrasounds.

Question 3

In a stable infant found to have hydronephrosis, or genitourinary, or kidney abnormalities on prenatal ultrasound, when should a follow-up ultrasound be obtained?

Answer 3

Wait until 1 week of age, if however, there is a concern of being unable to follow-up at 1 week, then obtain at discharge and at 4 to 6 weeks of age.

Question 4

If the patient is unstable or oliguric at birth then when should an ultrasound be obtained?

Answer 4

+At greater than or equal to 48 hours after birth

Question 5

What percentage of prenatal hydronephrosis demonstrates resolution postnatally??

Answer 5

50% postnatal ultrasounds demonstrate resolution

Question 6

What percentage of prenatal hydronephrosis postnatally is not associated with urinary tract obstruction?

Answer 6

15% of postnatal ultrasounds show persistent hydronephrosis not associated with urinary tract obstruction. Of these only 10% will require surgery due to development of obstruction, the rest will resolve entirely by age 3 years.

Question 7

What percentage of prenatal hydronephrosis postnatally is associated with obstructive or refluxing?

Answer 7

35% of postnatal ultrasounds show obstructive or refluxing causes.

Question 8

What are some of the underlying etiologies for obstructive or refluxing causes of hydronephrosis?

Answer 8

1. Ureteropelvic junction obstruction or UPJ
2. Vesicoureteral reflux or VUR
3. Posterior urethral valves or PUV
4. Megaureter
5. Ureterocele

Question 9

How is the severity of hydronephrosis graded?

Answer 9

It is based on measuring the anterior posterior pelvic diameter

Question 10

What constitutes a normal or mild hydronephrosis?

Answer 10

Less than 10 mm AP pelvic diameter

Question 11

What constitutes moderate hydronephrosis?

Answer 11

10 to 15 mm AP pelvic diameter

Question 12

What constitutes severe hydronephrosis?

Answer 12

Greater than 15 mm AP pelvic diameter

Question 13

In an infant who has not urinated in the first 48 hours or oligoanuria, what is strongly suggested diagnosis?

Answer 13

Genitourinary obstructive lesion.

Question 14

What physical exam findings may be present in an infant or newborn with genitourinary or kidney abnormalities?

Answer 14

Palpable abdominal or flank mass: UPJ or multicystic, dysplastic kidney
Distended bladder: PUV or urethral stricture
Absent abdominal musculature and undescended testes: Prune-belly syndrome

Question 15

When should a voiding cystourethrogram or VCUG be obtained?

Answer 15

If postnatal hydronephrosis is present on ultrasound and for evaluating VUR, ureterocele, urethral stricture, or PUV.

Question 16

What is a MAG-3 study?

Answer 16

Diuretic renography

Question 17

When should a MAG3 study be done?

Answer 17

In patients with hydronephrosis and a UPJ obstruction is suspected

Question 18

How should a patient with normal or mild hydronephrosis be managed?

Answer 18

Clinically with no further evaluation needed

Question 19

How should the patient with moderate hydronephrosis be managed?

Answer 19

A repeat ultrasound at 4 to 6 months of age is recommended.

Question 20

With the 4 to 6-month ultrasound results what further management is necessary for patients with resolution, no change or increasing hydronephrosis?

Answer 20

1. With resolution of hydronephrosis no further management needed, most will resolve by 18 months of age.
2. No change in hydronephrosis continue to monitor with an ultrasound at 1 year of age followed by an ultrasound at 3 to 5 years of age. May need to obtain a mag–3 renography if symptomatic, pain with urination or increasing urinary frequency to rule out obstructive process.
3. Increasing hydronephrosis, obtain a mag–3 study to look for obstructive process.

Question 21

How should the patient with severe hydronephrosis be managed?

Answer 21

Obtain diuretic renography or mag–3 at 6 weeks of age and refer to pediatric urologist.

Question 22

Should a child be circumcised routinely if found to have hydronephrosis?

Answer 22

Circumcision should not routinely be recommended for neonates with hydronephrosis, there is no evidence of negative renal outcomes and uncircumcised children with hydronephrosis.

Question 23

Although controversy in prophylactic management for hydronephrosis what antibiotics are used for what patient age and degree of hydronephrosis.

Answer 23

Amoxicillin or cephalexin is used in infants less than 3 months of age
TMP sulfa or nitrofurantoin is used in children greater than 3 months of age. Generally antibiotic prophylaxis is not used in infants with low-grade or moderate grade hydronephrosis.

Question 24

What 4 circumstances would most centers opt for providing antibiotic prophylaxis in neonates or children with hydronephrosis?

Answer 24

1. Dilated ureters
2. Enlarged bladder due to PUV
3. Bilateral UPJ obstruction
4. Giant hydronephrosis: Renal pelvis diameter greater than 30 mm