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

Hydronephrosis is not a condition but a symptoms 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:

  • A birth defect that causes a narrowing of the tube that leads from the kidney to the bladder
  • Kidney stones
  • Blood clots
  • Tumors
  • Scar tissue or injury to the urinary tract

Kidney, Ureter, Bladder, and Kidney Stone

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Other conditions that may cause problems with urine flow include:

  • Reflux—urine to flows back into the kidneys from the bladder
  • Abnormal bladder function due to problems with the nerves

In most cases, the child is born with one of these conditions that affect the urinary tract. For some, the condition develops later on.

Risk Factors

Male babies are more likely to have this complications than females.


In mild cases, there may not be any symptoms. If the condition is more severe, symptoms may include:

  • Pain in the back, waist, lower abdomen, or groin
  • Recurrent urinary or kidney infections
  • Persistent pain with urination or urinary frequency
  • Increased urge to urinate or urinary incontinence
  • Fever
  • Nausea and vomiting
  • Unexplained itching

The doctor will ask 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. The diagnosis may be confirmed with images of the kidneys. Images may be taken with:

  • Ultrasound —may be done before birth
  • Voiding cystourethrogram—x-rays of the bladder and urethra taken during urination
    • Note: This test is not done routinely in children aged 2-24 months.

Urine and blood tests may also be done to look for any changes in kidney function.

Other tests may be done to look for the cause of the hydronephrosis. This may include:


Hydronephrosis that develops before birth will often resolve on its own without kidney damage. The doctor will continue to monitor the kidneys until the swelling has gone away.

When necessary, the condition causing the back up of urine will be treated. This may include surgery or medication.

If the hydronephrosis is causing painful symptoms and there are signs of kidney damage, the urine may need to be drained. A tube may be placed through the skin to the kidneys to allow the urine to drain.


In many cases, hydronephrosis cannot be prevented. If your child has bladder problems talk to the doctor about methods to make sure the bladder empties as needed.


American Kidney Fund

National Kidney Foundation


BC Children’s Hospital

The Kidney Foundation of Canada


Hydronephrosis. Children’s Hospital Boston website. Available at: Accessed June 25, 2013.

Hydronephrosis. University of California Davis Health System website. Available at: Accessed June 25, 2013.

Hydronephrosis. University of California San Francisco Benioff Children's Hospital website. Available at: Accessed June 25, 2013.

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

Last reviewed March 2014 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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