Hydronephrosis

We understand that you may have a lot of questions when your child is diagnosed with hydronephrosis:

• What is it?
• What are the treatments?
• How will it affect my child long-term?

We’ve tried to provide some answers to those questions here, and when you meet with our experts, we can talk with you more about your child’s specific situation.

In all children with hydronephrosis, there is a backup of urine that causes the kidney to swell. How far the kidney is stretched, and how much the urinary flow is affected, will indicate how severe your child’s condition is.

• Mild: Your child usually will not experience symptoms; kidney function will be only slightly affected; and the condition usually resolves itself.
   
• Moderate: Your child may have some symptoms, but typically the kidney function will not decrease and the condition itself will not get any worse.
   
• Severe: Your child may experience symptoms such as urinary tract infections and pain in his side or abdomen. There is also greater risk for damage to kidney function. But remember, these effects may take months or even years to occur, or may never occur.

How common is hydronephrosis?

Hydronephrosis is a relatively common congenital condition (meaning a child is born with it), with some estimates showing it affects about 1 in 500 babies.

It’s often spotted on routine prenatal ultrasounds—at our Advanced Fetal Care Center, hydronephrosis is by far the most common urinary tract abnormality that we deal with. Less often, it goes undetected until an older child begins to experience symptoms.

Who is at risk for hydronephrosis?

While boys are about four to five times more likely to be born with hydronephrosis than girls, there are no known risk factors. It hasn’t been tied to genetic influences, meaning that if you have a child with hydronephrosis it’s not likely that your other children will have it.

And neither hydronephrosis nor its underlying causes have been linked to anything that parents did during pregnancy. In short, there is nothing you could have done to cause or prevent your child’s condition.

(Note: Hydronephrosis is not always congenital. It can also develop as a result of injury or other illness, such as kidney stones, but this is very rare.)

When should I seek medical advice?

Hydronephrosis is often discovered during routine prenatal ultrasound testing, but not always. If your infant has a urinary tract infection (UTI), it could indicate some kind of obstruction or reflux in the urinary system. However, UTIs can be difficult to spot in infants—in many cases, an unexplained fever is the only sign.

Older children may have more recognizable symptoms of urinary tract infection: strong urge to urinate, painful urination, cloudy urine, etc. If your child tends to get repeat UTIs, you may want to have him evaluated for possible urinary tract obstruction.

What complications are associated with hydronephrosis?

The most common complication of hydronephrosis is urinary tract infection—specifically, kidney infection (pyelonephritis), caused by bacteria spreading from the bladder. In children with a severe form of the condition and/or when it affects both kidneys, complications can include kidney damage, renal enlargement and even kidney failure.

Causes

In Greek, hydronephrosis translates as “water in the kidney.” It describes your child’s condition—a kidney overfilled with urine—but isn’t causing it. Instead, one of a number of other factors is at work here.

There are two main types of problems that cause hydronephrosis. One is obstruction, where urine is physically prevented from draining out of the kidney. The obstruction, or blockage, can be located at any point in the urinary system, from the kidney down to the urethra. The second is reflux, in which urine flows back up into the kidney.

Types of obstruction

• Ureteropelvic junction obstruction (UPJ): A blockage at the point where the kidney joins the ureter (the thin tube that carries urine to the bladder). Usually, this is caused by a narrowing at the top of the ureter.
   
• Ureterovesical junction obstruction (UVJ): A blockage at the point where the ureter joins the bladder.
   
• Posterior urethral valves (PUV): A congenital condition, found only in boys, in which there are abnormal flaps of tissue in the urethra (the tube that carries urine out of the body) that obstruct the bladder. Also associated with vesicoureteral reflux, below.
   
• Ureterocele: A bulge in the ureter that can obstruct part of the kidney and sometimes the bladder.

Types of reflux

• Vesicoureteral reflux (VUR): A backwash of urine that happens when the muscles at the junction of the ureter and bladder aren’t working properly, and allow urine to flow back up toward the kidney.

Other causes

Hydronephrosis may also be caused by such things as an ectopic ureter (in which the ureter doesn’t connect to the bladder). But in more than half of the children who are prenatally diagnosed with hydronephrosis, the condition resolves itself and the cause is never known.

Signs and symptoms

Most babies with hydronephrosis have no symptoms. Older children may also have no symptoms if they have mild or moderate hydronephrosis, and the condition may disappear on its own.

If your child has moderate to severe hydronephrosis, however, he may experience one or more of the following:

• pain in the abdomen
• pain in the side (also called flank pain)
• blood in the urine (hematuria)
• urinary tract infection (UTI)

Symptoms of a urinary tract infection can include a strong urge to use the bathroom, painful urination, cloudy urine, back pain, fever and vomiting.

FAQ

Q: How soon can hydronephrosis be seen on a prenatal ultrasound?

A: A baby’s kidneys begin to produce urine at about 10 to 12 weeks after conception, but it’s usually not until the fourth month or later that doctors can see signs of hydronephrosis.

Q: Do I need to ask for a special kind of prenatal ultrasound to check for hydronephrosis?

A: No—doctors can look for signs of hydronephrosis and other conditions in routine ultrasounds during your pregnancy.

Q: What can a prenatal ultrasound tell us about my baby’s condition?

A: Ultrasound is extremely useful in detecting signs of hydronephrosis, but remember that fetal tissue is very elastic—which means a swelling in the kidney may look worse on ultrasound than the condition really is. That is why your doctor will keep a close eye on the size of the fetus and the kidneys, as well as the level of amniotic fluid, throughout your pregnancy.

Q: Can prenatal hydronephrosis pose a serious risk to my baby?

A: In very rare cases, the condition will impair the flow of fetal urine to the point that there will be too little amniotic fluid (oligohydramnios). In that case, surgery may be required to drain the urine from your baby’s bladder and allow it to flow into the amniotic sac.

Q: If my baby has hydronephrosis, will I still have a normal delivery?

A: In the vast majority of cases, a finding of hydronephrosis won’t have any effect on either your pregnancy or your delivery.

Q: After I deliver my child, what happens next?

A: Doctors will likely prescribe a small daily dose of antibiotics (amoxicillin) to be taken at least until your child’s first evaluation, within two to three weeks.

Q: Does this mean my other children will have hydronephrosis?

A: No—hydronephrosis doesn’t run in families and has never been linked to anything the parents did during pregnancy.

Q: Will my child need dialysis because of hydronephrosis?

A: No, not if at least one of your child's kidneys is functioning normally.

Q: I’ve heard a lot about robotic-assisted surgery—can I request that for my child?

A: While robotic-assisted surgery can offer a number of benefits over and above traditional surgery, it isn’t recommended for every hydronephrosis patient. If your child needs an operation, your doctor will work with you to decide on the surgical approach best suited for him based on age and the underlying cause of his hydronephrosis.

Questions to ask your doctor

After your child is diagnosed with hydronephrosis, you may feel overwhelmed with information. It can be easy to lose track of the questions that occur to you.

Lots of parents find it helpful to jot down questions as they arise—that way, when you talk to your child’s doctors, you can be sure that all of your concerns are addressed.

Some of the questions you may want to ask include:

• How will my baby’s hydronephrosis affect my pregnancy?
• What tests will my baby need after he is born?
• Will my child need an operation?
• Are there signs I should watch for that my child’s hydronephrosis may be getting worse?

Useful medical terms

Bilateral: affecting two sides. Used to describe hydronephrosis that affects both kidneys.

Hydronephrosis: a swelling of the kidney caused by excess urine

Hydroureter: a swelling of the ureter caused by excess urine

Kidney scan (MAG 3): a nuclear scanning test that helps measure the difference in function between the two kidneys and also estimate the degree of blockage in the urinary system

Posterior urethral valves (PUV): a congenital condition in which there are excess flaps of tissue in the urethra, obstructing the bladder

Pyeloplasty: an operation that removes an abnormally narrow portion of the ureter and reconnects the rest to the kidney’s drainage system. One of the most common operations for hydronephrosis.

Renal: related to the kidneys

Renal ultrasound (RUS): a kind of ultrasound test that shows the size, shape and position of the kidney

Unilateral: affecting one side. Used to describe hydronephrosis that affects a single kidney.

Ureter: a long, narrow tube that carries urine from the kidney to the bladder

Urethra: the tube through which urine travels from the bladder out of the body

Urinary system: Made up of the kidneys, ureters, bladder and urethra, it filters waste from the body and removes it in the form of urine.

Unilateral: affecting one kidney only (common)

Ureterocele: a bulge in the ureter that can obstruct part of the kidney and sometimes the bladder

Ureteropelvic junction obstruction (UPJ): a blockage in the urinary system at the point where the kidney joins the ureter

Ureterovesical junction obstruction (UVJ): a blockage in the urinary system at the point where the ureter joins the bladder

Vesicoureteral reflux (VUR): an abnormal flow of urine from the bladder back into the ureter and sometimes the kidneys

Voiding cystourethrogram (VCUG): a type of x-ray that shows the flow of urine through a patient’s bladder and urethra during urination