Hydronephrosis is caused when urine flow is blocked, making the kidneys swell. Swelling usually affects only 1 kidney (unilateral), but it can affect both (bilateral). This condition can also be accompanied by swelling of the ureter (hydroureter).

Patients can be seen by Texas Children's experts in Urology.

Causes & Risk Factors

The urinary tract includes 2 kidneys, 2 ureter tubes, a bladder, and a urethra. This is the body's drainage system for removing waste and extra water. Urine should flow in one direction down from the kidneys, through the ureter tubes, to the bladder and out the urethra.  Hydronephrosis is caused when this urine flow is blocked.

Urine flow blockage in children may be caused as a result of:

  • narrowing of the ureter tube from an injury or birth defect
  • a kink in the urteropelvic junction (where the ureter tube meets the kidney)
  • reverse flow of urine from the bladder back to the kidneys (reflux)

As well as other causes, such as:

  • surgery
  • radiation therapy
  • kidney stones
  • blood clots
  • retroperitoneal fibrosis (a rare disorder that blocks the ureter tubes)
  • tumors in or near the ureter tube 

Symptoms & Types

Often many patients have no symptoms associated with their hydronephrosis.  A common symptom of hydronephrosis is urinary tract infection (UTI). Patients often mistake a serious urinary infection for the flu.

Symptoms of UTI may include:

  • painful, burning urination
  • blood in the urine
  • weak urine stream
  • cloudy urine
  • pain in the back, side, or groin
  • fever, sweats, chills, and generalized discomfort

There are 2 types of hydronephrosis: acute and chronic.

Acute hydronephrosis:This is the most common type. Symptoms develop quickly over just a few hours.

Symptoms can include:

  • intense, severe pain in the back or side (between the ribs and the hip)
  • swelling or mass in the stomach area
  • nausea and vomiting
  • fever
  • UTI
  • painful urination (dysuria)
  • increased urgency and frequency of urination

Chronic hydronephrosis: With chronic hydronephrosis, urine flow blockage develops slowly over weeks or months. This is often painless with few or no symptoms. If there are symptoms, they can be the same as those for acute hydronephrosis (see above) or they may be just be a dull pain that comes and goes.

If you see signs of hydronephrosis, schedule an appointment with your child's doctor immediately. Untreated UTIs may lead to more serious conditions such as infection of the kidney and kidney scarring.

Diagnosis & Tests

While hydronephrosis is often discovered after birth, it is also discovered before the baby is born (when it is still a fetus) through an ultrasound. Hydronephrosis is the most common urological problem found during prenatal ultrasound screening. As many as 42,000 fetuses (1.4% of all fetuses) are diagnosed with hydronephrosis each year.[1] This is usually detected in the first trimester of pregnancy.

But just because hydronephrosis is discovered on ultrasound doesn't mean that your child will be born with hydronephrosis. Fetal kidneys can strengthen during their development in the womb and the condition may disappear.

Your newborn will need to be evaluated for bulges and swelling. Soon after birth, your newborn may need imaging tests to confirm her condition. These tests can include:

Generally, about 25% of children who have improper function or poor kidney drainage will require surgical intervention.1

 [1]Weill Cornell Medical College, Department of Urology. "Pediatric Urology: Prenatal Hydronephrosis." https://www.cornellurology.com/clinical-conditions/pediatric-urology/pr…

Treatment & Care

Treatment for hydronephrosis is primarily focused on getting rid of whatever is obstructing the flow of urine. Treatment may include:

  • pyeloplasty (surgery to reconstruct and repair the urinary tract)
  • antibiotics for UTI infections
  • ureteral stent (a thin tube inserted into the ureter to prevent or treat obstruction of urine flow)
  • nephrostomy tube (to drain blocked urine through the back)
  • insertion of a urinary or suprapubic catheter (to treat lower urinary tract obstruction)
  • removal of affected area and reconnection of the ureter (if condition is caused by scar tissue or blood clot)
  • kidney stone surgery (if the cause is kidney stones)

Children who have only one kidney, who have immune-compromising disorders such as diabetes or HIV, or who have received a transplant, should be treated promptly.

Living & Managing

After the urine flow has been unblocked, the kidney may react with a brief flood of urine. Normal kidney function should return. Even if one kidney is destroyed, the other will compensate for the lost organ and function normally.

Kidney stones can be prevented by dietary changes and medication. Prompt evaluation of infections and urinary complaints will usually detect problems early enough to prevent long-term complications in your child.

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References & Sources