Understanding Hydronephrosis in Newborns

Hydronephrosis in newborns is an enlargement or swelling of the kidneys. Depending on the cause, it can be either mild or severe. It may resolve without treatment, but some children may need medications or surgery.

Hydronephrosis is a swelling of one or both kidneys. It can happen when urine is unable to properly drain from the body and builds up in the kidneys.

Hydronephrosis is a common birth irregularity in newborns. It’s often diagnosed before birth and can affect up to 2 out of every 100 fetuses. It can be the result of a blockage in the urinary tract tubes or a physical irregularity causing poor urine flow.

Learn more about hydronephrosis .

What is hydronephrosis in newborns?

Hydronephrosis in newborns is an enlargement or swelling of the kidneys.

It occurs in the area where urine collects, called the renal pelvis. This prevents urine from draining properly from the body. It can happen in one or both kidneys and sometimes clears up on its own.

Hydronephrosis in newborns is usually discovered in pregnancy, often during a prenatal ultrasound. If discovered early, doctors will examine how urine is draining from the fetus’ kidneys and monitor the condition.

A more severe case of hydronephrosis could indicate a blockage in the urinary tract and require treatment once the fetus is born.

Normally, fetal urine mixes with the amniotic fluid in the womb. In severe hydronephrosis, too much urine stays in the body, leading to low levels of amniotic fluid. This could potentially cause difficulty with fetal lung development.

Once the infant is born, unresolved hydronephrosis could lead to kidney stones, urinary tract infections, and chronic kidney disease.

What are the signs and symptoms of hydronephrosis in newborns?

Newborns do not usually show signs or symptoms of hydronephrosis.

If the hydronephrosis does not resolve before birth, symptoms that could appear include abdominal swelling, which would indicate a severe blockage of the urinary tract, and urinary tract infection (UTI) , which include symptoms include fever, abdominal pain, or foul-smelling urine.

What causes hydronephrosis in newborns?

There’s often no known cause for hydronephrosis in fetuses and newborns. This is usually the situation with mild cases that clear up on their own, called transient hydronephrosis. These account for about 50% of cases diagnosed before birth.

It’s believed that a narrowing in the urinary tract during fetal development causes transient hydronephrosis. As the urinary tract matures, the hydronephrosis resolves. If hydronephrosis has not resolved before birth, it may sometimes still be transient and clear up by the time the child is 3 years old.

There are occasions where a birth irregularity may cause hydronephrosis. Even in these cases, the condition will often resolve.

Sometimes, specific birth irregularities may cause more severe hydronephrosis. These conditions include:

• Lower urinary tract obstruction: This occurs when there is a blockage in the urethra or where the bladder joins the urethra. Birth irregularities that can cause this include posterior urethral valves or an abnormal fold of tissue that blocks the urethra. This issue is only seen in males. This can be an urgent issue for doctors to examine, as a lower urinary tract obstruction will block urine flow from both kidneys.
• Urinary tract or other body area irregularities: Issues in the urinary tract or other body areas may lead to hydronephrosis. Sometimes, birth irregularities affecting the spinal cord may affect the nerves controlling the urinary tract, possibly leading to urinary reflux and hydronephrosis.

• Ureter changes: These issues in the ureter may cause hydronephrosis:
  • Ureteropelvic junction (UPJ) obstruction: A blockage occurs where the ureter meets the renal pelvis.
  • Vesicoureteral reflux (VUR): VUR occurs when urine flows backward (refluxes) from the bladder to the ureters or the kidneys.
  • Other ureter issues: Issues here or where the ureter and bladder meet may prevent the normal flow of urine.

Of these ureter issues, UPJ and VUR are the most likely to cause hydronephrosis in newborns.

What are the risk factors for hydronephrosis in newborns?

There are no known risk factors for hydronephrosis in newborns. However, some newborns with certain birth irregularities are more likely to develop hydronephrosis. These irregularities include:

• Prune belly syndrome: This is a group of irregularities that include poorly developed abdominal muscles, urinary tract irregularities, and undescended testicles.
• Spina bifida: This condition affects the spinal cord and the nerves that control the urinary tract.

How is hydronephrosis diagnosed in newborns?

Hydronephrosis is often diagnosed during a prenatal ultrasound. If hydronephrosis is detected during a prenatal ultrasound, it will be monitored throughout the pregnancy.

A diagnosis in newborns is based on the infant’s prenatal medical history, physical exam, and imaging.

During the physical exam, a doctor will look for any abdominal lumps that could indicate an enlarged kidney or bladder. They will also investigate the rest of the body for any potential irregularities.

Imaging tests that highlight the urinary tract will be used to diagnose and identify the cause of hydronephrosis. These tests include:

• Ultrasound: In this test, sound waves create an image of the urinary tract.
• Voiding cystourethrogram: This test uses X-rays to show the path of urine through the bladder and urethra.
• Radionuclide scan: This test shows the urinary tract as a radioactive substance passes through.

How is hydronephrosis treated in newborns?

Mild cases of hydronephrosis may not need treatment. The typical treatment strategy for hydronephrosis in newborns will depend on how severe the condition is, how many kidneys are affected, and what’s causing it.

The general treatment protocol for hydronephrosis in newborns includes:

• Watchful waiting: If the condition is not severe and the kidneys are not at risk, this is a popular treatment method for newborns. Periodic tests will be performed to monitor the condition and see if it improves and goes away or worsens. If it worsens, surgery could be needed.
• Treating and preventing UTIs: Antibiotics may be prescribed to prevent UTIs in babies with hydronephrosis. These medications will also be used to treat a UTI in the event that one develops. For male infants with hydronephrosis, research suggests that circumcision may lower the risk of UTIs.
• Surgery: Surgery may be recommended if an infant’s hydronephrosis is severe or worsens. This can improve urine flow and lower the risk of complications. Surgery is typically not performed on a fetus still in the womb, as the risks are too high.

What’s the outlook for newborns with hydronephrosis?

The outlook for newborns with hydronephrosis is usually good. Most cases of hydronephrosis are mild and will resolve in time without treatment.

For those that require treatment, preventing or treating UTIs or surgery will usually resolve the condition without long-term health complications.

If the condition is not monitored or treated, hydronephrosis complications can include urinary tract infections, kidney stones, and, in severe untreated instances, chronic kidney disease.

Frequently asked questions

Is hydronephrosis in newborns serious?

Hydronephrosis in newborns is usually not serious. In many cases, it will resolve on its own, but sometimes, the condition may require medications or surgery.

Can drinking water help hydronephrosis?

Drinking water is good for kidney health, but infants under 6 months old should not be given water unless advised by their pediatrician.

Breastmilk or infant formula provides all the hydration needed by a newborn. Most infants with hydronephrosis do not need to (and should not) have their fluid intake limited.

Takeaway

Hydronephrosis in newborns is a common urinary tract irregularity often diagnosed before birth.

It results in swollen or enlarged kidneys and can cause difficulty in urine flow. The cause is often unknown, but certain birth irregularities could result in more severe hydronephrosis.

Its primary complication is frequent urinary tract infections, but it could lead to kidney damage if not properly monitored.

Most cases of hydronephrosis in newborns resolve on their own, but occasionally, doctors may prescribe medication. Surgery may be needed to clear any urinary tract blockages.