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  • Cynthia M. Johnson, MA
Publication Type:




Hydronephrosis is when one or both kidneys swell with backed up urine. This swelling can lead to kidney infection or kidney harm.

Hydronephrosis is a symptom of another health issue.

Urinary Tract System.

si55551330_urinary tract child.jpghttp://services.epnet.com/getimage.aspx?imageiid=81278127si55551330_urinary tract child.jpgsi55551330_urinary tract childNULLjpgsi55551330_urinary tract child.jpgNULL\\hgfiler1\intellect\images\si55551330_urinary tract child.jpgNULL13NULL2010-07-233593318127_616684Copyright © Nucleus Medical Media, Inc.


Hydronephrosis is caused by urinary tract problems that make it hard for urine to leave the kidneys. Urine may be slowed or stopped by:

  • A blockage, bulge, or narrowing in the tube that carries urine from the kidney to the bladder
  • In boys, flaps of tissue blocking the tube that carries urine out of the body or narrowing of the tip of the penis

Other health issues that may cause problems include:

  • Urine flowing backward from the bladder into the kidneys
  • Problems with the tube that carries urine to the bladder or in the way that it connects
  • An abnormal kidney may sometimes cause problems

Children are often born with one of these health issues that affect the urinary tract. For some, the problem appears later on. Sometimes the cause of hydronephrosis is not known.

Risk Factors

Hydronephrosis is more common in boys than girls.


A child with hydronephrosis may have:

  • Pain in the back, sides, belly, or groin
  • Blood in the urine
  • Trouble feeding
  • Poor growth
  • Signs of urinary tract infection
    • Urine that has a strong smell
    • Vomiting
    • Fever
    • Blood in the urine
    • Irritability


Most often hydronephrosis is diagnosed during an ultrasound before the child is born.

After birth the doctor will ask about symptoms and health history. A physical exam will be done. A swollen kidney may be able to be felt at the physical exam.

Urine tests and blood tests may be done.

Imaging tests may be done to look for blockages and other problems. These tests may include:

  • Ultrasound—may be done before and after birth
  • Voiding cystourethrogram—x-rays of the bladder and urethra taken during urination that are only done if hydronephrosis is still an issue after birth
  • MRI scan
  • CT scan
  • Cystoscopy


Hydronephrosis that starts before birth will often go away on its own without hurting the kidney. It may go away before or after birth. A child's kidneys will be watched until the swelling has gone away.

A health issue that is causing the urine backup will be treated. Treatment options may include:


Hydronephrosis cannot be prevented.


The doctor may advise:

  • Over the counter medicine to reduce pain or fever
  • Antibiotics to prevent or treat an infection


The doctor may advise:

  • Over the counter medicine to reduce pain or fever
  • Antibiotics to prevent or treat an infection


Surgery may be needed if:
  • The hydronephrosis is causing a lot of pain
  • There are signs of kidney damage
  • There is a problem such as a blockage that will not go away on its own
The type of surgery that is done depends on what is causing the hydronephrosis. Very rarely surgery may need to be done before birth.




  • Hydronephrosis. Boston Children’s Hospital website. Available at: https://www.childrenshospital.org/conditions/hydronephrosis.
  • Hydronephrosis. University of California Davis Health System website. Available at: http://www.ucdmc.ucdavis.edu/urology/downloads/kurzrock_handouts_PDF/Hydronephrosis.pdf.
  • Hydronephrosis. University of California San Francisco Benioff Children's Hospital website. Available at: http://www.ucsfbenioffchildrens.org/conditions/hydronephrosis.
  • Värelä, S., Omling, E., et al. Resolution of hydronephrosis after pyeloplasty in children. Journal of Pediatric Urology, 2021; 17 (1): 102.E1-102.E7.
  • Vesicoureteral reflux. EBSCO DynaMed website. Available at: http://www.dynamed.com/condition/vesicoureteral-reflux-vur.


  • Chelsea Skucek, MSN, BS, RNC-NIC
Last Updated:

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.