What Is Nephrotic Syndrome?

Nephrotic syndrome happens when there's too much protein in urine (pee) because of a kidney problem. This causes:

• swelling in parts of the body like the face, hands, belly, and feet
• sudden weight gain

Most of the time, nephrotic syndrome goes away with medicine, and kids outgrow it by the time they're teens.

What Causes Nephrotic Syndrome?

Nephrotic (neh-FROT-ik) syndrome happens when tiny filters in the kidneys called glomeruli (gluh-MARE-you-lie) leak too much protein into urine. It can happen at any age, but is most common in kids 1–6 years old. It affects boys more than girls.

What Are the Signs & Symptoms of Nephrotic Syndrome?

Swelling and weight gain tend to be the most common signs. Swelling happens because too many fluids and salt build up in the body. Extra fluids can cause weight gain. Parents might notice their child quickly outgrows clothes and shoes.

Swelling most often happens in the:

• face, especially around the eyes (this is most noticeable in the morning)
• ankles and feet, especially after sitting or standing a long time
• belly

Other common signs include loss of appetite, peeing less often, and pee that looks dark and foamy.

Some kids don't have any symptoms. They may learn they have nephrotic syndrome when a routine urine test finds the condition.

What Happens in Nephrotic Syndrome?

Glomeruli are balls of tiny blood vessels (capillaries) that help remove waste products from the blood. When the filters stop working correctly, too much protein gets into pee.

Protein helps hold fluids in the blood. With less protein in the blood, fluids can move to other parts of the body and cause swelling in the face, belly, hands, arms, and feet.

Many things can damage the glomeruli and cause nephrotic syndrome. But in kids it's usually due to minimal change disease. The damage to the glomeruli is so small (or "minimal") that it can be seen only under a strong microscope called an electron microscope.

Why kids get minimal change disease isn't always known. It is believed to be due to an immune system problem. Often, it happens after an infection. Most kids outgrow minimal change disease by their teen years, with no kidney damage.

Rarely, kids can get other types of nephrotic syndrome due to things like:

• cancer and tumors
• taking too many over-the-counter medicines like ibuprofen
• obesity

How Is Nephrotic Syndrome Diagnosed?

Doctors diagnose nephrotic syndrome with urine tests and blood tests. 

If a child has nephrotic syndrome, the doctor will look for the cause, then decide how best to treat it. The doctor also might:

• order other blood tests
• take a tiny sample of kidney tissue (a kidney biopsy) to test for specific causes of the condition

How Is Nephrotic Syndrome Treated?

Nephrotic syndrome is almost always treatable, but the treatment depends on the cause. Kids with nephrotic syndrome usually are treated by a nephrologist (a doctor who specializes in kidney problems).

To treat minimal change disease, the doctor will prescribe:

• Prednisone. This medicine works well to treat nephrotic syndrome, but can sometimes have side effects. The doctor may prescribe other medicines to ease or prevent them.
• A diuretic. This makes a child pee more often, which can help control the swelling until protein levels return to normal.

Kids should eat a low-salt diet to help ease swelling. A low-protein diet isn't necessary. For other dietary advice, talk to a doctor or dietitian.

If prednisone treatment doesn't lower the protein levels in the urine, the doctor will do a kidney biopsy to look for other causes of the condition.

What Else Should I Know?

Minimal change disease causes most cases of nephrotic syndrome in kids. Those who get prednisone usually respond well, and the problem goes away by the time they're teens. In the meantime, kids might need to take medicines for a few months or more.

Sometimes, a child will have a relapse. This means the nephrotic syndrome comes back after going away. In this case, treatment starts again until the child outgrows the condition or it improves on its own.

The sooner treatment for nephrotic condition starts, the better. If your child shows any signs of the condition, call your doctor so it can get checked out right away.