Pediatric Hydronephrosis

Hydronephrosis (hy·​dro·​ne·​phro·​sis) is a swelling in the urinary tract.

At Children's Health℠, we have one of the nation’s top pediatric urology programs. We see more cases of hydronephrosis than almost any other center in our region, which means we have deep experience treating this condition. We offer kids and their families compassionate care every step of the way.


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What is Pediatric Hydronephrosis?

Fetal hydronephrosis is found in 1-5% of all pregnancies. It can be found on a prenatal ultrasound before a baby is born and is one of the most common conditions detected during prenatal screening ultrasounds. It can also be diagnosed after a baby is born or in older children.

Hydronephrosis can be a sign of a wide variety of conditions. It can range from a minor swelling that does not need treatment to a more severe condition that requires surgery.

The swelling happens when one or both tubes carrying urine from the kidneys to the bladder (called ureters) become blocked or when urine backs up from the bladder to the kidney.

Hydronephrosis happens more often in males than females. It can affect one or both kidneys. In most cases, it goes away on its own.

What are the signs and symptoms of Pediatric Hydronephrosis?

In hydronephrosis detected during pregnancy, imaging shows swelling in the baby’s kidneys or bladder.

With mild hydronephrosis in babies and younger children, there usually is no pain. With moderate and severe swelling in older children, the symptoms can include:

How is Pediatric Hydronephrosis diagnosed?

During pregnancy, a fetal or prenatal ultrasound at 18-20 weeks can detect swelling. If this happens, we can use follow-up ultrasounds to see if the swelling is increasing or decreasing, how the kidneys are developing, and if the ureters or bladder are dilated. With severe swelling, we will do more frequent ultrasounds, and we may do an MRI. We also may assess the amount of amniotic fluid in the uterus. Amniotic fluid mostly consists of urine from the fetus, so not having a lot of fluid in the uterus can mean the baby has severe obstruction or concerns about kidney function.

In infants or in children, we may do different kinds of imaging to monitor and assess hydronephrosis:

  • Ultrasound: Images from sound waves that can detect swelling in the urinary tract
  • Voiding cystourethrogram (VCUG): A specialized X-ray that can detect urine backing up from the bladder to the kidney (reflux) or a blockage (obstruction) in the bladder. This imaging involves placing a catheter into the bladder.
  • Kidney scan (Mag-3): Which can evaluate how severe obstruction is and whether it has affected the kidneys
  • MRI: Which creates detailed imaging that may be used to find what’s causing severe hydronephrosis

We also may do genetic testing to look for conditions that may cause hydronephrosis, in cases where other organs may be affected.

What causes Pediatric Hydronephrosis?

Hydronephrosis can be caused by a blockage at any part of the urinary system. It also may be caused by urine backing up from the bladder to the kidney, called vesicoureteral reflux. In most cases, the swelling goes away on its own, and the exact cause is never known, but probably is due to slower maturation of the urinary tract.

Hydronephrosis during pregnancy is not caused by anything that a parent did, and it may have genetic causes that scientists don’t yet understand. In older children, hydronephrosis can be caused by a range of conditions, including kidney stones.

How is Pediatric Hydronephrosis treated?


When hydronephrosis is detected during pregnancy, we make a care plan for monitoring and treatment. Most babies don’t need to be delivered early or need surgery. If the amniotic fluid is low, we may do a procedure to help increase the flow of urine.

Follow-up imaging

When hydronephrosis is detected during pregnancy, we will examine the baby after birth. In mild cases, we usually recommend follow-up imaging at two to six weeks.

Renal ultrasound

An infant with severe hydronephrosis on both sides of the urinary tract will probably get a renal ultrasound and more testing in the first few days of life.


We may also use a low dose of an antibiotic to prevent a urinary tract infection (UTI).


We often monitor infants or children for months or even years to see if the swelling and other symptoms change. We recommend surgery if their hydronephrosis gets worse or if the function of the kidneys is affected.

We may do a procedure called a pyeloplasty, which removes a blockage of the ureter. We do this procedure with robotic-assisted laparoscopy, where we use highly precise tools to remove the blockage without a large scar on the abdomen.

For infants with hydronephrosis and another complex condition, such as spina bifida or prune belly syndrome, we may recommend other surgical procedures.

In general, your child’s treatment will depend on how serious their condition is. Our team will use their deep experience with hydronephrosis to select the best care plan for your child. Because it so often resolves on its own, we take a cautious approach to identify severe cases and avoid over-treatment.

Pediatric hydronephrosis doctors and providers

Our care teams include pediatric urologists and nephrologists, neonatologists and nurse practitioners who specialize in urology. We have extensive experience working with hydronephrosis and other conditions of the urinary tract.

Frequently Asked Questions

  • Can hydronephrosis go away without harming my baby?

    Mild hydronephrosis usually goes away on its own. Because it can be hard to predict whether a child will have mild or severe hydronephrosis symptoms, we usually monitor children with this condition carefully.

  • Is my baby in pain?

    In babies, even severe obstruction doesn’t cause pain, which is why it can be hard to tell if there’s a problem. Children may have a range of symptoms, including difficulties urinating or urinating completely.

  • If one of my baby’s kidneys is obstructed because of hydronephrosis, will my baby wet fewer diapers?

    Even if one of your baby’s kidneys is obstructed, they will still produce as much urine as if both of their kidneys were working. They will still wet just as many diapers.