Dayton Children’s Hospital

Hydronephrosis

What is hydronephrosis?

Hydronephrosis is a condition that happens in the womb when one or both of your baby’s kidneys becomes swollen with urine.

There are two types of problems that usually cause this:

  • Obstruction: Urine can’t drain out of the kidney because of a blockage at some point in the urinary system.
  • Vesicoureteral reflux (VUR): Urine flows back up into the kidney because the muscles at the point where the bladder meets the ureter (the tube that carries urine between the kidney and the bladder) don’t work properly, similar to a “leaky valve.”

Depending on how enlarged the kidney is or how much urine has built up, hydronephrosis could be mild, moderate or severe. One common complication associated with severe hydronephrosis is urinary tract infection, but it can also cause kidney damage.

Hydronephrosis is fairly common and happens in about 1 in 100 babies. Boys tend to be more likely to have hydronephrosis than girls.

How is the condition diagnosed?

The condition is diagnosed by ultrasound during pregnancy. It is usually diagnosed around the fourth month of pregnancy. During the ultrasound, your doctor will be able to see the shape of your baby’s kidneys, look at the amount of amniotic fluid in the womb and see what’s blocking the urine.

In 50 percent of cases where mild hydronephrosis appears on the ultrasound, the issue resolves by itself by the time the baby is born or very soon after, without any intervention

Most babies with hydronephrosis do not have other birth defects or physical problems. If other problems are seen, we may recommend that you talk with our genetic counselors.

How is hydronephrosis managed?

During your pregnancy it is important to follow your baby’s condition to assess if the condition is worsening, and the amount of amniotic fluid. We will schedule a prenatal appointment with a pediatric urologist who will review your baby’s ultrasound exams. The pediatric urologist will explain the post-delivery evaluation and treatment options. Usually, early delivery is not required and your baby can go to full term. Babies with hydronephrosis do not require a cesarean delivery for this condition.

In rare cases, fetal intervention may be necessary if the level of amniotic fluid in the womb becomes too low. If the baby’s life is at risk, your doctor will put a shunt (tube) into a large needle. Then, the large needle is put into your abdomen and goes directly into the baby’s enlarged bladder. This purpose of this shunt is to let the urine that’s trapped in the bladder to empty out into the amniotic sac. After your baby is born, he or she will need more surgery to protect the kidneys and help the bladder drain properly

To help determine the cause of hydronephrosis, multiple tests may be performed. Some tests are on blood drawn from the baby and some tests are special x-ray like tests. Often the baby will have an ultrasound, similar to what you had during pregnancy, to look at the size, shape and location of the kidneys. Another test is called a voiding cystourethrogram, this test is performed by placing a small catheter into the bladder, instilling a special solution that shows up on x-ray and evaluating if urine can back up into the kidneys and how severe this back up is if it occurs.

When urine backs up into the kidneys it is called vesicouretheral reflux or VUR for short. VUR can be mild, moderate or severe in nature. VUR/hydronephrosis can be associated with varying degrees of renal failure. If there is concern for how the kidneys are working, a special test called a renal scan may be performed. This test is designed to help us gauge how well the kidney is filtering and excreting by-products from the body.

Treatment for hydronephrosis will be based on your baby’s specific situation. Neonatologists, urologists and nephrologists will work together to create the treatment plan. Most babies with hydronephrosis will take antibiotics to help prevent or treat infection while others may need additional treatments such as surgery. In addition to these treatments nutrition will be very important, sometimes special diets to improve growth will be prescribed.

How will hydronephrosis affect my baby during and after surgery?

If your baby requires surgery, it will be done either during the hospitalization immediately after birth or at a later time after you go home. Our pediatric urologists will be able to discuss the prognosis for your baby with you and develop the treatment plan that is best for your situation.