Hydronephrosis is when one or both kidneys swell with backed up urine. This swelling can lead to kidney infection or kidney damage.
Hydronephrosis is not a condition but a symptom of another condition.
Urinary Tract System
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Hydronephrosis is caused by urinary tract problems that makes it difficult for urine to leave the kidneys. Urine may be slowed or blocked by:
Other conditions that may cause problems with urine flow include:
In most cases, the child is born with one of these conditions that affect the urinary tract. For some, the condition develops later on. Sometimes the cause of hydronephrosis is not known.

Risk Factors

Hydronephrosis is more common in boys than girls.


Hydronephrosis may cause:


Most often hydronephrosis is diagnosed during pregnancy during a maternal ultrasound.
After birth you will be asked about your child’s symptoms and medical history. A physical exam will be done. Your doctor may be able to feel the swollen kidney during the physical exam.
Your child's bodily fluids may be tested. This can be done with:
Imaging tests evaluate bodily structures. These may include:


Hydronephrosis that develops before birth will often resolve on its own without kidney damage, either before or after birth. Your child's kidneys will be monitored until the swelling has gone away.
When necessary, the condition causing the back up of urine will be treated. Treatment options may include:


Medications may include:
  • Over-the-counter medication to reduce pain and/or fever
  • Antibiotics to prevent or treat infection


If the hydronephrosis is causing painful symptoms, there are signs of kidney damage, and there is a correctable lesion that will not get better on its own surgery may need to be done to allow urine to flow properly. The type of surgery that is done depends on the cause of your child's hydronephrosis. In rare cases, surgery may need to be done before birth.


There are no current guidelines to prevent hydronephrosis.


American Kidney Fund

National Kidney Foundation


BC Children’s Hospital

The Kidney Foundation of Canada


Herz D, Merguerian P, et al. Continuous antibiotic prophylaxis reduces the risk of febrile UTI in children with asymptomatic antenatal hydronephrosis with either ureteral dilation, high-grade vesicoureteral reflux, or ureterovesical junction obstruction. J Pediatr Urol. 2014;10(4):650-654.

Hydronephrosis. Boston Children’s Hospital website. Available at: Accessed March 10, 2016.

Hydronephrosis. University of California Davis Health System website. Available at: Accessed March 10, 2016.

Hydronephrosis. University of California San Francisco Benioff Children's Hospital website. Available at: Accessed March 10, 2016.

Vesicoureteral reflux. EBSCO DynaMed website. Available at: Updated August 25, 2015. Accessed March 10, 2016.

4/1/2014 DynaMed's Systematic Literature Surveillance Choosing wisely. EBSCO DynaMed website. Available at: Updated March 26, 2014. Accessed August 13, 2014.

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