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: An obstruction, bulge, or narrowing in the tube that carries urine from the kidney to the bladderIn 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 kidneysProblems with the tube that carries urine to the bladder or in the way that it connectsOccasionally, 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 groinBlood in the urine Trouble feedingPoor growthSymptoms 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.
Your child's bodily fluids may be tested. This can be done with: Urine testsBlood tests
Imaging tests evaluate bodily structures. These may include: Ultrasound—may be done before and/or after birth
Voiding cystourethrogram—x-rays of the bladder and urethra taken during urination Note: This test is only done if there is hydronephrosis still present after birth. MRI scanCT scanCystoscopy
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 feverAntibiotics 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 March 10, 2016.
Hydronephrosis. University of California Davis Health System website. Available at:
http://www.ucdmc.ucdavis.edu/urology/downloads/kurzrock_handouts_PDF/Hydronephrosis.pdf. Accessed March 10, 2016.
Hydronephrosis. University of California San Francisco Benioff Children's Hospital website. Available at:
http://www.ucsfbenioffchildrens.org/conditions/hydronephrosis/index.html. Accessed March 10, 2016.
Last reviewed March 2016 by Kari Kassir, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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