Hydronephrosis, the increase in fluid around the kidneys, is a condition that causes one or both kidneys to swell because of excess urine. This condition is very common; in fact, hydronephrosis is the most common abnormality detected on prenatal ultrasounds and accounts for 50% of all prenatally found birth defects. While the prenatal ultrasounds are used to see the baby’s kidneys are enlarged, they do not always indicate a blockage. After the baby is born, about half will have normal kidney functions where the other half may indicate signs of hydronephrosis.
It is important to know that the first few months following birth are critical for the baby’s kidney development, and any damage during this time may lead to structural and functional defects. The most serious problems from hydronephrosis can include damaged lung development and kidney malfunction. As a result, prenatal detection as well as neonatal follow up is key to see if there are any indications of hydronephrosis.
Sonograms are typically used to check for:
- Discrepancies in fundal height for gestational age
- High levels of a protein called alpha-fetoprotein in the mother’s blood
- Previous pregnancies with birth defects
A gestational prenatal ultrasound is used to check for:
- Fetal size and maturity
- Amniotic fluid volume
- Basic check of the head, spine, heart, lungs, limbs and abdomen
- Kidney position, size and texture
- Appearance of ureters and collecting system
- Bladder volume, wall thickness and emptying
- Examination of other pelvic organs
- Appearance of external genitalia
Pediatric Hydronephrosis Symptoms
There may be no obvious signs or symptoms of pediatric hydronephrosis in newborns, or even before a child is born. The first indication of this condition may be after having a prenatal ultrasound done during routine check-ups.
Older children may experience more bothersome symptoms including:
- Recurrent urinary tract infections (UTIs)
- Hematuria, or blood in the urine
- Abdominal pain
Causes & Risk Factors for Pediatric Hydronephrosis
The most common cause of pediatric hydronephrosis is ureteropelvic junction (UPJ) obstruction, which is the blockage where the renal pelvis connects to the ureter. This may be caused by the intrinsic narrowing of the proximal ureter, similar to a scar or stricture where the ureter exits the kidney, or the ureter being obstructed by a band of tissue or a blood vessel supplying the lower part of the kidney, known as a "crossing vessel." Other causes may include:
- Vesicoureteral reflux: When urine flows backward from the bladder into the kidney
- Megaureter: An abnormally large ureter involving massive reflux
- Posterior urethral valves: Extra tissue in the urethra that blocks urine
- Renal pelvic dilation: Varying degrees of dilation in the renal pelvis
Prevention Strategies for Pediatric Hydronephrosis
There is no exact way to prevent pediatric hydronephrosis. With that said, some ways to manage the severity include:
- Pre-and post-delivery evaluation and follow-up
- Close monitoring of the child after birth to avoid any infections
- Meeting with your care team to address and treat the underlying cause
Evaluation and Treatment for Pediatric Hydronephrosis
Evaluation for pediatric hydronephrosis occurs before and after a child is born. This includes:
- Pre-delivery: Standard prenatal ultrasounds and testing. If such tests show decreased amniotic fluid, genital malformations or other serious anomalies, the child should be treated at a tertiary care center for delivery and neonatal management.
- Post-delivery: If pediatric hydronephrosis is indicated on the prenatal ultrasounds, a thorough physical examination including a newborn ultrasound performed between 48 hours to one month of age will be carried out. Based on the ultrasound results, a VCUG (Voiding Cystourethrogram) may be ordered, which is an x-ray test involving dye inserted into the bladder and taking x-rays while the child empties the bladder to check for abnormalities and urinary reflux.
- Outpatient evaluation: Most postnatal evaluations can be done on an outpatient basis. Children with moderate prenatal hydronephrosis usually go home on amoxicillin without further inpatient evaluation. For these babies, an ultrasound may be performed 3-4 weeks after birth while they continue antibiotic prophylaxis.
- Evaluation for severe cases: A diuretic renography is needed to assess renal obstruction and function if the prenatal ultrasounds severe pelvic dilation (over 1.2 cm) and caliectasis. This test is typically done after the baby is at least one month old.
In most cases where hydronephrosis is found before birth, the condition resolves on its own. With that said, treatment for pediatric hydronephrosis depends on the underlying cause and may include:
- Surgical and Medical Management: Managing post-natal urinary tract obstruction due to UPJ (Ureteropelvic Junction). While safe and effective interventions exist, there is controversy over when and if surgery is necessary due to the limitations of sonography and renography in accurately assessing the degree of obstruction and kidney function.
- Surgical Intervention: About 25% of children with diminished kidney function or poor drainage will eventually need surgery. Management strategies vary from close observation with regular check-ups to immediate repair of any obstruction if delayed drainage is detected.
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