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 make it difficult for urine to leave the kidneys. Urine may be slowed or blocked by:
- An obstruction, bulge, or narrowing in the tube that carries urine from the kidney to the bladder
- In boys, flaps of tissue obstructing the tube that carries urine out of the body or narrowing of the tip of the penis
Other conditions that may cause problems with urine flow include:
- The backwards flow of urine from the bladder into the kidneys
- Problems with the tube that carries urine to the bladder or in the way that it connects
- Occasionally, an abnormal kidney
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.
Hydronephrosis is more common in boys than girls.
Hydronephrosis may cause:
- Pain in the back, sides, abdomen, or groin
- Blood in the urine
- Trouble feeding
- Poor growth
- Symptoms of urinary tract infection
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.
Urine tests and blood tests may be done.
Imaging tests evaluate bodily structures. These may include:
—may be done before and/or after birth
Voiding cystourethrogram—x-rays of the bladder and urethra taken during urination
This test is only done if there is hydronephrosis still present after birth.
- MRI scan
- CT scan
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.
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: http://www.childrenshospital.org/health-topics/conditions/hydronephrosis. Accessed January 28, 2021.
Hydronephrosis. University of California Davis Health System website. Available at: http://www.ucdmc.ucdavis.edu/urology/downloads/kurzrock_handouts_PDF/Hydronephrosis.pdf. Accessed January 28, 2021.
Hydronephrosis. University of California San Francisco Benioff Children's Hospital website. Available at: http://www.ucsfbenioffchildrens.org/conditions/hydronephrosis/index.html. Accessed January 28, 2021.
Vesicoureteral reflux. EBSCO DynaMed website. Available at: http://www.dynamed.com/topics/dmp~AN~T116455/Vesicoureteral-reflux. Accessed January 28, 2021.
4/1/2014 DynaMed Plus Literature Surveillance http://www.ebscohost.com/dynamed: Choosing wisely. EBSCO DynaMed website. Available at:http://www.dynamed.com/topics/dmp~AN~T116455/Vesicoureteral-reflux. Updated July 23, 2015. Accessed March 20, 2018.
Last reviewed March 2020 by
EBSCO Medical Review Board
Chelsea Skucek, MSN, BS, RNC-NIC
Last Updated: 1/28/2021