How Reflux Nephropathy Silently Damages Kidneys in Children

Reflux nephropathy is a condition that results from kidney damage and loss of kidney function due to the backward flow of urine from the bladder into the kidneys. "Reflux" means backward flow, and "nephro" means relating to the kidneys.

Your kidneys produce urine and send the urine through your ureters to your bladder. Urine isn't supposed to flow backward into the kidneys. Over time, backward flow can cause damage and scarring in the kidneys.

What causes reflux nephropathy?

Reflux nephropathy results from the backward flow of urine into your kidneys. This backward flow is called "vesicoureteral reflux (VUR)."

People with VUR have ureters with faulty valves that don't fully close, allowing this backward flow of urine. VUR is often congenital, which means the faulty valve is present from birth. Genetics may contribute to congenital VUR, but scientists have yet to identify a specific gene that causes it.

Doctors usually diagnose VUR in children under the age of 2 years. Many babies outgrow VUR without ever getting symptoms or complications. Having urinary tract infections (UTIs) during childhood is the most common sign of VUR.

Although rare, some people also develop VUR later in life. VUR can occur due to increased pressure within the bladder and ureters.

Still, not everyone who has VUR develops reflux nephropathy.

Who gets reflux nephropathy?

Reflux nephropathy primarily affects children or young adults.

People born with VUR are most at risk of reflux nephropathy. This risk increases if repeat UTIs occur during childhood or later, especially when treatment is delayed.

Although it's unclear how many children have VUR, experts estimate it affects 0.4-1.8% of children. About 30-54% of those children may develop kidney scarring.

Just like VUR, reflux nephropathy can also be congenital or acquired. Some people may be born with scarring and reduced kidney function, while others may develop it later in childhood.

Acquired VUR is more common among people assigned female at birth, but congenital reflux nephropathy is more common among people assigned male at birth.

Conditions that block the outward flow of urine can cause acquired reflux nephropathy in people born with normally functioning urinary tracts. These conditions include:

• enlarged prostate
• bladder stones
• neurogenic bladder that results from advanced diabetes and neurological disorders such as Parkinson's disease

In some instances, your ureters may become damaged or swollen, which increases your risk of acquired reflux nephropathy. Damaged or swollen ureters may be due to injury or a risk of kidney transplant surgery.

What are the symptoms of reflux nephropathy?

Reflux nephropathy is often asymptomatic.

When symptoms and signs do occur, they may be similar to those related to end stage renal disease (ESRD), such as:

• fatigue
• swelling around the eyes (periorbital edema)
• restless legs syndrome
• swollen legs
• shortness of breath

One of the most common symptoms of reflux nephropathy is recurrent UTIs. Children may also wet the bed frequently.

Symptoms of UTIs include:

• fever
• vomiting
• painful urination
• burning sensation during urination
• bloody urine
• fussiness (in babies)

What are the possible complications of reflux nephropathy?

Reflux nephropathy can sometimes lead to chronic kidney disease (CKD) in children or adults.

Experts estimate that reflux nephropathy is responsible for the development of CKD in 7-17% of children and 10% of adults with ESRD, the last stage of CKD. But recent research suggests that these numbers have been decreasing in recent decades.

High blood pressure (hypertension) occurs in 10-30% of children and young adults with this condition. According to experts, high blood pressure may be more common in males with reflux nephropathy than in females.

Hyperkalemia (high potassium) may also occur in people who have reflux nephropathy. Fetal death (stillbirth) can also occur in pregnant people with advanced disease and renal scarring.

How do doctors diagnose reflux nephropathy?

To diagnose this condition, a healthcare professional may recommend blood and urine tests to check your kidney function. They may also rely on imaging tests of the kidneys and urinary tract for diagnosis. In some instances, they may discover this condition inadvertently during routine testing or pregnancy.

Blood and urine tests for reflux nephropathy include:

• blood urea nitrogen test
• complete blood count
• creatinine blood test
• creatinine clearance urine test (urine 24-hour volume test)
• urine culture

Imaging tests include:

• ultrasounds of the kidneys and bladder
• abdominal CT scan
• intravenous pyelogram and retrograde pyelogram
• radionuclide cystogram
• voiding cystourethrogram

What is the treatment for reflux nephropathy?

A doctor may prescribe daily antibiotics to children with VUR to prevent UTIs, which may help avoid kidney damage. But 2019 research suggests that antibiotics may not make much of a difference.

Controlling your blood pressure also helps slow down the progression of kidney damage. A doctor may recommend medications that reduce high blood pressure, such as angiotensin converting enzyme inhibitors and angiotensin II receptor blockers.

If medical treatments aren't enough to reduce VUR symptoms, a doctor might recommend surgery to repair the ureter. Surgery can help stave off and treat reflux nephropathy.

If there's already severe kidney damage, a doctor may recommend medications to treat CKD. Slightly less than half of people with ESRD from reflux nephropathy require a kidney transplant.

Lifestyle changes may also be helpful. Examples include:

• quitting smoking, if you do
• reducing alcohol intake
• eating a low protein diet
• avoiding salt

What is the outlook for people with reflux nephropathy?

The outlook for people with reflux nephropathy varies based on the severity of their condition.

In people with mild disease, kidney function may remain typical. If there's only damage in one kidney, the other kidney should continue to function as it should.

In people with severe disease, kidney failure may occur. About 1 in 3 people with ESRD due to reflux nephropathy die within 5 years of diagnosis.

People who wish to pursue pregnancy may want to discuss their options with a specialist before conception, if possible.

Takeaway

Reflux nephropathy refers to kidney damage and scarring from VUR: the backward flow of urine into the kidneys from the bladder.

The condition is often the result of a congenital issue in the urinary tract. Adults with underlying conditions that affect the bladder and kidneys may also acquire reflux nephropathy.

Treatment in children often centers on the prevention of UTIs. Without treatment, reflux nephropathy can lead to CKD.