Nephrotic syndrome happens when tiny structures in the kidneys called glomeruli (gluh-MARE-you-lie) stop working properly and let too much protein enter the kidneys. In kids, this is usually due to a kidney condition called minimal change disease that affects the glomeruli. Nephrotic syndrome is more common in boys than girls, especially in kids younger than age 5.
Fortunately, most cases (including those caused by minimal change disease) can be effectively treated with medicine. Most kids who get nephrotic syndrome as a result of minimal change disease eventually outgrow it by the teen years.
How the Kidneys Work
The kidneys are a pair of bean-shaped organs located toward the back of the abdominal cavity, just above the waist. The kidneys remove waste products and extra water from the food a person eats, returning chemicals the body needs (such as sodium, phosphorus, and potassium) back into the bloodstream. The extra water combines with other waste to become urine (pee).
The main functional units of the kidneys, where the blood filtering happens, are tiny organs called nephrons. Each kidney has about a million nephrons, and each nephron has one glomerulus (singular of glomeruli) — a ball of tiny blood vessels, or capillaries. The glomerulus is the nephron’s filter. This is where the process of removing waste products and fluids from the blood begins.
When the glomeruli stop filtering properly, they allow too much protein to leave the blood. Protein helps hold fluids in the blood, so when there is less protein in the blood, the fluids can move to other parts of the body and cause a type of swelling (edema) in the face, belly, hands, arms, and other extremities. When this happens, it’s called nephrotic syndrome.
A number of conditions can damage the glomeruli and cause nephrotic syndrome. But in kids it’s usually due to minimal change disease. With minimal change disease, the glomeruli don’t appear to be affected when viewed under a regular microscope. That’s why the condition gets the name “minimal change.” The changes to the glomeruli can only be seen under an electron microscope.
The cause of minimal change disease isn’t known, but it can be related to infections, tumors, allergic reactions, and excessive use of over-the-counter medications like ibuprofen and acetaminophen. Fortunately, most kids outgrow minimal change disease by the time they’re in their teens.
Other conditions can damage the glomeruli, including other kidney conditions, immune system problems, infections, or diseases like cancer and diabetes. In certain cases, an allergic reaction to food or a bee sting, the use of certain legal and illegal drugs, or morbid obesity can lead to nephrotic syndrome.
Some kids have no obvious symptoms of nephrotic syndrome and don’t know they have the condition until after it’s been diagnosed through a urine test.
When symptoms do appear, swelling and weight gain tend to be the most common. Swelling happens as excess fluids and salt build up in the body. Often, this can be enough to bring on a rapid, unintentional increase in weight.
The most common places for swelling are:
- in the face, especially around the eyes
- in the abdomen (belly)
- in the arms and legs, particularly around the ankles and feet
Some kids with nephrotic syndrome notice swelling around their ankles after they’ve been standing or sitting for a long time. Others may notice more swelling around their eyes first thing in the morning. Other common signs include loss of appetite, diarrhea, less frequent urination, and urine that looks dark and foamy.
In rare cases, the condition causing nephrotic syndrome can lead to other symptoms and complications, like kidney damage with kidney failure, thrombosis (blood clots in the blood vessels), or infection due to a loss of proteins that help fight infections.
If your child has symptoms of nephrotic syndrome, see a doctor. The doctor will probably ask your child for a urine sample to check for too much protein. The doctor also might take a small blood sample for testing.
If the tests indicate that your child has nephrotic syndrome, the doctor will determine what the underlying cause is and then decide on how best to treat it. This may require your child to undergo additional blood tests. In rare cases, the doctor may need a tiny sample of kidney tissue to test for specific causes of nephrotic syndrome. This is known as a kidney biopsy.
Nephrotic syndrome is almost always treatable, but the treatment depends on the cause. To treat minimal change disease, doctors usually prescribe a medicine called prednisone. One of prednisone’s functions is to suppress the body’s immune system, which can help the glomeruli work the way they’re supposed to.
Prednisone is very effective at treating nephrotic syndrome, but it can sometimes have side effects. Doctors often prescribe additional medicines to ease or suppress side effects when someone takes prednisone.
In some cases, nephrotic syndrome does not respond to prednisone. When this happens, the doctor may want to do a kidney biopsy to determine the cause. Other causes of nephrotic syndrome may be treated by other medicines or therapies.
When kids have nephrotic syndrome, doctors may prescribe a medicine called a diuretic to help them pee more often. This can help control the swelling in the body until protein levels in the blood return to normal.
At home, kids should eat a low-salt diet to help reduce swelling. Reducing the amount of protein in a child’s diet is not necessary. For other dietary suggestions, talk to a doctor or nutritionist.
Fortunately, in most kids with nephrotic syndrome the condition goes away for good by the time they’re teens and doesn’t damage the kidneys. In the meantime, kids might need to take medicines for a few months or more.
Sometimes, a child will have a relapse — where the nephrotic syndrome comes back after going away. In that case, treatment would begin again until the child outgrows the condition or it improves on its own.
Reviewed by: Robert S. Mathias, MD
Date reviewed: March 2014