Conditions + Treatments

Hydronephrosis in Children

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Hydronephrosis is a condition where urine overfills, or backs up, into the kidney, which causes the kidney to swell. Infants with hydronephrosis may be diagnosed before (prenatal) or after (postnatal) birth. Learn more about how Boston Children's Hospital treats prenatal and postnatal hydronephrosis.

If your baby is diagnosed with hydronephrosis, here are a few helpful things to know:

  • In many of the children who are diagnosed prenatally, the condition disappears spontaneously by the time of birth or soon after.
  • In children who have mild or, sometimes, moderate hydronephrosis, kidney function is commonly unaffected and the condition may resolve over a period of time after delivery.
  • We are here to help. At Boston Children’s, our physicians and nurses are trained in pediatric urology and have extensive experience with hydronephrosis. We are ranked #1 in the nation and have the largest pediatric urology service in the world.

Caregiver Profile: Richard Lee, MD

Key facts

  • Hydronephrosis affects the drainage of urine from the urinary system—the kidneys, ureters, bladder and urethra. When the urinary system is impaired, this can cause the urine to back up and the kidney to swell.
  • Hydronephrosis affects about 1 in 100 babies.
  • Hydronephrosis is typically caused by either something blocking urine flow or by urine leaking backward through the urinary system (reflux). Identifying the cause of your child’s hydronephrosis will help determine how we recommend treating it.
  • Your doctor will describe your child’s hydronephrosis as mild, moderate or severe. This description is based on how much the kidney is stretched and how much the urinary flow is impaired. Your doctor will tell you whether your child’s hydronephrosis affects one kidney (unilateral) or both kidneys (bilateral).
  • Hydronephrosis can be detected via ultrasound. More than half of the cases resolve by the time the baby is born or soon after.
  • In children who have mild or, sometimes, moderate hydronephrosis, kidney function is frequently unharmed.
  • The likelihood of surgery depends on the cause and severity of your child’s hydronephrosis. Surgery for mild cases is unlikely. For moderate cases, surgery occurs 25 percent of the time. Children with severe hydronephrosis will need surgery 75 percent of the time.
  • If surgery is required, our success rate is 95 percent successful and unsurpassed.
  • Hydronephrosis is not always congenital. It can develop as a result of injury or other illness, such as kidney stones.

We are grateful to have been ranked #1 on U.S. News & World Report's list of the best children's hospitals in the nation for the third year in a row, an honor we could not have achieved without the patients and families who inspire us to do our very best for them. Thanks to you, Boston Children's is a place where we can write the greatest children's stories ever told.”
- Sandra L. Fenwick, President and CEO

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