What is hydronephrosis?"Hydronephrosis is a condition that involves 1 or both of the kidneys. Kidneys work to make urine. Each kidney has 2 parts:

●A part that filters blood – This part removes waste and excess salt and water, leading to the formation of urine.

●A part that collects urine – This part then sends the urine down the urinary tract, which includes the bladder.

In hydronephrosis, the part of the kidney that collects urine has too much urine in it. This causes it to swell and get bigger than normal.

Some babies have hydronephrosis that lasts only for a short time and then goes away. This condition is not serious and doesn't cause any long-term problems.

If the hydronephrosis doesn't go away, it could be caused by a serious problem in the urinary tract. For example, there might be a blockage in the urinary tract, or urine might flow backward from the bladder to the kidney. When urine flows backward, it is called "reflux." Babies with reflux are at higher risk for kidney infections. Infections can lead to permanent kidney damage.

How do I know if my baby has hydronephrosis?Hydronephrosis in babies is usually found "prenatally." This means during pregnancy, before the baby is born.

Doctors find out that a baby has hydronephrosis when they do an ultrasound to check on the baby during pregnancy. An ultrasound creates pictures of the baby inside the uterus.

Hydronephrosis does not cause any symptoms unless the baby gets a kidney infection.

Will I need more tests?Yes. If your baby has hydronephrosis, your doctor will want to see if it goes away or not, or gets worse. You will have 1 or more ultrasounds to follow up during your pregnancy.

When your doctor does an ultrasound, they will check:

●If 1 or both kidneys have hydronephrosis

●How severe the condition is

●Your amniotic fluid – Amniotic fluid is the fluid in the uterus that surrounds the baby. It is made up of the baby's urine. If a problem keeps the kidneys from making enough urine, the amount of amniotic fluid will be low.

If the follow-up ultrasound shows that the hydronephrosis has gone away, you probably won't need any more tests.

If the follow-up ultrasound shows that the hydronephrosis has not gone away or is worse, you will likely need more tests. These can include more ultrasounds or tests to look for other conditions.

How is prenatal hydronephrosis treated during pregnancy?Doctors follow the condition with tests, but they do not usually treat it.

How is hydronephrosis treated after birth?It depends on how severe the condition is:

●If the hydronephrosis went away before birth, your baby will not need any tests or treatment after birth.

●If the hydronephrosis did not go away, your baby's doctor will do an ultrasound after birth. This can show how severe the hydronephrosis is.

●Babies with mild hydronephrosis usually do not need any treatment unless they have a kidney infection. The doctor might do another ultrasound when the baby is 4 to 6 months old. If the hydronephrosis goes away by then, the baby will not need any more tests or treatment.

●For babies with more severe hydronephrosis or kidney infections, the doctor will do other tests to check the urinary tract. This might include a something called a "diuretic renal scan" or a "voiding cystourethrogram" ("VCUG"). Some babies might get both. These are imaging tests that can tell if there is a blockage or reflux. Your doctor will tell you which test is right for your baby.

Your baby's doctor might also prescribe an antibiotic medicine. This medicine can help prevent kidney infections. Some babies might need other treatments, depending on their test results. For example, if there is a severe blockage in the urinary tract, the baby might need surgery to fix the problem. Most babies with reflux can be treated without surgery, though surgery is sometimes needed if the reflux is severe.