What You Know About Hydronephrosis in newborns?

What is hydronephrosis in newborns?

Hydronephrosis in newborns is an enlargement or dilation of the renal pelvis, the funnel in the central part of the kidney where urine collects. 

Hydronephrosis can occur in one or both kidneys . 

This condition is often diagnosed before birth, during a prenatal ultrasound .

In some cases, hydronephrosis is mild and goes away on its own without treatment. In other cases, hydronephrosis may be a sign of a blockage in the urinary tract , or reflux or accumulation of urine from the bladder into the kidney that needs treatment.

The urinary tract is the body’s drainage system for removing toxins and excess fluid. 

The urinary tract includes the kidneys , ureters, bladder, and urethra also.

The urinary tract, which includes the kidneys, bladder, ureters, and urethra.
The urinary tract includes the kidneys, ureters, bladder, and urethra

Does hydronephrosis have other names?

Hydronephrosis may have other names, including:

  • Antenatal, fetal, or prenatal hydronephrosis, when the condition is diagnosed before birth
  • dilated or enlarged urinary tract

How common is hydronephrosis in newborns?

In 1 or 2 of every 100 pregnancies hydronephrosis in the fetus is diagnosed. 

In about half of these cases, hydronephrosis has already disappeared when the baby is born. two

Who is more likely to develop hydronephrosis?

Boys are about twice as likely as girls to have hydronephrosis. 

Is hydronephrosis a sign of a problem?

If a fetus or newborn is found to have hydronephrosis, healthcare professionals will examine how urine drains from the kidneys. The more severe the hydronephrosis, the more likely it is a sign of urinary tract obstruction or reflux of urine from the bladder to the kidney, which may require treatment. 

Early diagnosis and treatment of obstruction or reflux can help prevent complications or prevent complications from getting worse.

Normally, the urine of the fetus becomes part of the amniotic fluid that surrounds the fetus in the womb. 

In a fetus with severe hydronephrosis, too much urine may remain in the urinary tract, causing low levels of amniotic fluid in the uterus. 

Low levels of amniotic fluid can damage the lungs of the developing fetus.

After the baby is born, hydronephrosis can cause complications such as urinary tract infections , kidney stones,  and chronic kidney failure .

What are the signs or symptoms of hydronephrosis in a newborn?

Newborns with hydronephrosis often show no signs. 

In some newborns, the abdomen may be swollen due to severe urinary tract obstruction. 

In other cases, newborns with hydronephrosis may develop a urinary tract infection, which can cause signs or symptoms  .

If your child has been diagnosed with hydronephrosis, consult with your healthcare professional about appropriate evaluation and treatment options.

What Causes Hydronephrosis in Newborns?

In some fetuses and newborns with hydronephrosis, healthcare professionals cannot find the cause and the hydronephrosis goes away on its own. 

This is known as transient hydronephrosis.

In other cases, the cause of hydronephrosis is a blockage in the urinary tract or the backflow of urine from the bladder to the kidney.

Hydronephrosis transitoria

Experts believe that narrowing of a part of the urinary tract during early development can cause transient hydronephrosis. 

The situation resolves as the urinary tract matures.

About half of fetuses diagnosed with hydronephrosis have this transient form that disappears before birth. 

In children born with hydronephrosis, the condition is sometimes transient and may go away on its own, usually by 3 years of age. two

Birth defects

Birth defects in the urinary tract can cause hydronephrosis. Even when birth defects are the cause, hydronephrosis can be mild and get better as the child grows. However, birth defects can also cause hydronephrosis that is severe or worsens over time.

Ureter defects. Birth defects in the ureter that cause hydronephrosis include:

  • ureteropelvic junction obstruction, in which there is a blockage where the ureter joins the renal pelvis
  • vesicoureteral reflux (VUR) , in which urine is returned, or refluxed, from the bladder to one or both ureters and sometimes the kidneys
  • other defects in the ureter or at the junction of the ureter to the bladder, which can prevent the normal flow of urine from the kidneys to the bladder

Among all the birth defects that cause hydronephrosis in fetuses and newborns, ureteropelvic junction obstruction and VUR are the most common. 1

Lower urinary tract obstruction. In lower urinary tract obstruction, also known as bladder outlet obstruction, there is a blockage in the urethra or where the bladder joins the urethra. Birth defects that cause lower urinary tract obstruction include the posterior urethral valves, which are abnormal folds of tissue that block the urethra. Posterior urethral valves only occur in males. Since lower urinary tract obstruction blocks the flow of urine from both kidneys, it is more urgent for doctors to examine lower urinary tract obstruction than blockage or reflux in a ureter.

Defects in the urinary tract and other parts of the body. Some babies with hydronephrosis have birth defects in the urinary tract and elsewhere in their body. For example, prune belly syndrome is a group of birth defects that includes underdeveloped abdominal muscles, undescended testicles, and urinary tract defects.

Birth defects that affect the spinal cord, such as spina bifida , can affect the nerves that control the urinary tract and cause urinary retention  . Retained urine in the bladder can back up into the ureters and kidneys, causing hydronephrosis.

How do healthcare professionals diagnose hydronephrosis before the child is born?

Health care professionals can diagnose hydronephrosis before the baby is born during a prenatal ultrasound . Ultrasound bounces safe and painless sound waves off the fetus’ organs to create an image of their structure. An ultrasound can show which parts of the urinary tract are enlarged due to hydronephrosis.

Ultrasound scans during pregnancy are part of routine prenatal tests . If a fetus is diagnosed with hydronephrosis, healthcare professionals may recommend additional ultrasound scans to see if the hydronephrosis worsens or improves over time. Healthcare professionals may also use ultrasound or other prenatal tests to try to find the cause of hydronephrosis or detect other health problems.

How do healthcare professionals diagnose hydronephrosis in newborns?

Health care professionals use the newborn’s medical history, a physical exam, and imaging tests to diagnose hydronephrosis.

Clinic history

Health care professionals use the results of prenatal ultrasounds and other prenatal tests to determine what type of test or treatment babies will need after birth.

Physical exam

During the physical exam, the healthcare professional will look for a lump or mass in the abdomen, which could be a sign of an enlarged kidney or bladder; It will also look for signs of birth defects in other parts of the body.

Imaging tests

Healthcare professionals can use urinary tract imaging tests  to diagnose and find the cause of hydronephrosis. Imaging tests may include:

  • ultrasound, which uses sound waves to view your child’s urinary tract
  • voiding cystourethrogram, which uses x-rays to show how urine flows through the bladder and urethra
  • radionuclide scan , which creates images of the urinary tract as a radioactive substance passes

How do healthcare professionals treat hydronephrosis in newborns?

Treatment of hydronephrosis in newborns will depend on:

  • how serious the condition is
  • whether one or both kidneys are affected
  • what causes hydronephrosis

Treatments may include watchful waiting, prevention and treatment of urinary tract infections, and surgery.

Watchful waiting

If hydronephrosis in a newborn is not severe and is not likely to damage the kidneys, healthcare professionals may recommend watchful waiting and will do tests from time to time to see if hydronephrosis changes or causes kidney damage as as the baby grows.

Hydronephrosis can get better or go away over time. However, if hydronephrosis worsens or causes complications, your healthcare professional may recommend surgery.

Newborn seen by a healthcare professional
If hydronephrosis in a newborn is not severe and is not likely to damage the kidneys, the doctor may recommend watchful waiting.

Prevention and treatment of urinary tract infections

In some cases, healthcare professionals may prescribe antibiotics to help prevent urinary tract infections in infants and children with hydronephrosis. If a child develops a urinary tract infection, antibiotics are also used to treat the infection.

In male infants with hydronephrosis, research suggests that circumcision may reduce the chance of getting urinary tract infections. 4


If hydronephrosis is severe or worsens over time, healthcare professionals may recommend surgery. Surgery can improve urine flow and reduce the chance of complications or prevent complications from getting worse.

Healthcare professionals rarely perform surgery to treat hydronephrosis in a fetus while it is still in the womb. Fetal surgery carries many risks, which is why it is performed only in special cases.

Clinical trials for hydronephrosis in newborns

The NIDDK conducts and supports clinical trials for many diseases and conditions, including those of the urinary tract. Clinical trials look for new ways to prevent, detect or treat diseases and improve quality of life.

What are clinical trials and what role do children have in research?

Clinical trials are research studies that involve people of all ages. Clinical trials are looking for new, safe and effective ways to prevent, detect, or treat disease. Researchers also use clinical trials to look at other aspects of care, such as improving quality of life. Research with children helps scientists:

  • identify the best medical care for a child
  • find the best dose of medications
  • find treatments for conditions that only affect children
  • treat conditions that behave differently in children
  • understand how treatment affects a growing child’s body

Source URL: https://www.niddk.nih.gov/health-information/informacion-de-la-salud/enfermedades-urologicas/hidronefrosis-recien-nacidos
Source Agency: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)