When a pregnant woman goes for routine screening of her baby, healthy kidneys may not be the first thing she thinks about. But in 1 or 2 out of every 100 pregnancies, the fetus is diagnosed with a kidney condition called hydronephrosis.

“When parents hear their baby has prenatal hydronephrosis, they often look up the diagnosis online and see so many possibilities. It can be overwhelming,” said Stacy Tanaka, MD, Professor and Chief of Pediatric Urology at the University of Alabama at Birmingham. “The diagnosis can mean a lot of different things. That’s why it’s a good idea to consult with a pediatric urologist. They can explain the condition. They can give you an idea of what could happen even before the baby is born. In most cases, babies won’t need treatment. But in a small number of cases, babies will need treatment and long-term follow-up. We don’t want to miss these potentially life-threatening cases.”

The kidneys are fist-sized organs that make urine. They are found on both sides of the spine behind the liver, stomach, pancreas and bowels. Healthy kidneys work like clockwork to turn extra water and waste into urine. Urine flows out of the kidneys and into the ureters. These are thin tubes of muscle that connect the kidneys to the bladder.

Prenatal hydronephrosis is the swelling of the part of the kidneys that stores urine. The swelling causes a problem with the kidney’s urine collection system. Several things can go wrong with this system.

Prenatal hydronephrosis cannot be prevented. In about half of cases, the problem goes away by the time the baby is born. If the baby is born with hydronephrosis, the condition may go away over time, usually by age 3. The baby will need to go for checkups and may not need treatment.

In a smaller number of cases, the baby may need to be treated. If a serious case of hydronephrosis is not treated, it can lead to urinary tract infections, scarring or permanent kidney damage.

One type of prenatal hydronephrosis is called ureteropelvic junction (UPJ) obstruction. This happens when there is a blockage where urine flows out of the kidney and into the ureter. “The baby needs to be examined to see if surgery is recommended in the first few months,” Dr. Tanaka said. “In some cases the problem can be watched, and could get better on its own.”

Another type is called vesicoureteral reflux (VUR). This is a defect in the valve that normally stops urine from flowing back into the kidney. Some babies with this condition are given antibiotics to prevent a kidney infection. In a smaller number of cases, surgery is needed.

The most serious type of hydronephrosis occurs when tissue flaps called posterior urethral valves (PUV) block the urethra—the tube that carries urine from the bladder to the outside of the body. PUV affects the bladder and kidneys. PUV could lead to kidney failure if it is not treated with surgery as soon as the baby is born.

Most cases are diagnosed during an anatomy scan of the fetus. Prenatal hydronephrosis can also be diagnosed during an ultrasound later in the pregnancy. If an ultrasound detects the problem, the doctor may recommend more ultrasounds to find out if it is getting better or worse. “The doctor will provide the parents with counseling about what they can expect after the baby is born,” Dr. Tanaka said.

If the scans indicate the baby may need surgery, the doctor may recommend the mother give birth at a hospital with a tertiary care neonatal intensive care unit (NICU). They are equipped to provide advanced, complex treatments by medical specialists in state-of-the-art facilities. In less severe cases, the baby may need surgery, but not right away. In these cases, the mother doesn’t need to give birth at a tertiary care hospital.

Treatment depends on several factors. These include how severe the condition is and whether one or both kidneys are affected. Treatment options include watchful waiting, antibiotics and surgery.

If the hydronephrosis is not severe and is not likely to damage the kidneys, the doctor may recommend watchful waiting. This means the doctor will do tests from time to time to see if the condition changes or causes kidney damage as the baby gets older. If it gets worse or causes problems, the doctor may recommend surgery.

“After a year or so, if the doctor doesn’t see any problems developing, the child may not need to continue coming in for ultrasounds,” Dr. Tanaka said. “If the doctor sees a child’s kidney function declining, the child may need to come in more often.”

In some cases, a baby will be treated with antibiotics to prevent a kidney infection. The child will receive antibiotics in a low dose every day, possibly for months.

In a small percentage of cases, surgery is needed. The goal is to reduce swelling and pressure in the kidney by restoring the free flow of urine. In most cases, the surgery is done once the baby is born. Surgery on a fetus carries risks and is done only in special cases.

The most common surgery is done to fix UPJ obstruction. The surgeon removes the narrowed or blocked part of the ureter. Then the healthy portion is reconnected.

Other surgery may be recommended, depending on what is causing the problem and how severe it is. A child who has surgery needs checkups with a urologist throughout their life.

Dr. Tanaka says the vast majority of children with hydronephrosis grow up healthy and lead normal lives. “Even children who need surgery generally have good outcomes,” she said. “They lead normal, healthy lives.”

For more information, visit UrologyHealth.org. 

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