When you're hungry, your stomach lets out a growl or two. When you run around, your heart lets you know it's really working by boom, boom, booming! But some important body parts are quiet as a whisper. Psst — we're talking about your kidneys.

What Are the Kidneys?

Your kidneys are tucked under your lower ribs on either side of your spine. Each one is about the size of your fist and shaped like a bean. Most people have two kidneys, but they work so effectively that a person can be happy and healthy with only one.

Think that's cool? Check out their job: each day your kidneys act like high-powered filters for about 200 quarts (189 liters) of fluid in your flowing blood. That's enough fluid to fill 100 of those big soda bottles that hold 2 liters each!

Your kidneys remove waste and excess fluid that naturally builds up in your blood after your body breaks down food. The kidneys collect that stuff and send it on to the bladder as urine (pee), so you can get rid of it when you go to the bathroom.

Besides taking out your body's "trash," your kidneys help balance your body's vitamin and mineral levels so your other organs and bones can do their best work. They help in the production of red blood cells and produce a form of vitamin D, which promotes healthy bones. If that's not enough, they help keep your blood pressure at a healthy level.

Kinds of Kidney Diseases

Like any complicated machine, not all kidneys work perfectly. When someone's kidneys have problems for a long time, doctors call it a chronic kidney disease. Children's kidney problems are either congenital (say: kun-jen-uh-tul) or acquired (say: uh-kwired).

The difference is that a congenital problem exists from the day someone is born. An acquired kidney problem develops over time, often due to an injury, kidney infection, or other illness. Many congenital kidney problems are hereditary, which means they're passed down through a person's genes. Acquired kidney problems are not hereditary.

Two of the most common kidney problems are congenital. One of them is obstructive uropathy (say: ub-strukt-iv yur-ah-pah-thee). This means something is blocking urine flow and keeping the kidneys from doing their waste-removing job properly.

Another congenital problem is renal dysplasia (say: ree-nul dis-play-zhuh). A person with renal dysplasia was born with kidneys that are smaller than they should be or that didn't form correctly. This makes it difficult for the kidneys to work the way they should.

How Are Kidney Diseases Diagnosed?

Kidney problems are often not noticed at an early stage. As the illness progresses, someone with a kidney disease may feel tired, nauseated, itchy, or dizzy. The person also might have puffy eyes, ankles, or feet because the body has trouble getting rid of extra fluid. Someone who has these problems needs to go to the doctor.

At a doctor visit, the doctor would examine the person and ask questions about past and current health problems. Doctors can use many special tests to find out if someone's kidneys are working properly. Blood pressure can be measured — if it's high, it may indicate a kidney problem. Because the kidneys produce urine, the doctor can check a person's pee for blood or protein. Normal urine usually doesn't contain much of either one.

The doctor also might take a little bit of the person's blood to check the amount of something called creatinine (say: kree-at-in-een), a natural waste product that muscles release into the blood. The level of creatinine can go up too high if the kidneys aren't working well.

Some doctors check for growths or blockages by using machines that take special pictures, like X-rays, ultrasound scans, or CAT scans. To pinpoint the problem, a doctor may also do a biopsy (say: by-op-see). In this test, the doctor takes out a tiny piece of kidney tissue with a needle and looks at it under a microscope. Doctors and nurses will give medicine called anesthesia to keep the person comfortable during the biopsy.

How Do Doctors Treat Kidney Problems?

The treatment for chronic kidney problems depends on how well the kidneys are working. It may include vitamins, minerals, and medications to help with growth and to prevent bone disease. Sometimes unhealthy kidneys have problems producing a hormone that helps make red blood cells, the cells that carry oxygen to your body's tissues.

When a person doesn't have enough red blood cells, that's called anemia, which can make someone feel worn out. If this is a problem, the doctor may prescribe blood transfusions or medicine that helps the body make red blood cells.

Kids with kidney problems are more likely to get high blood pressure, which can be harmful if it isn't controlled. In those cases, a kid may have to take blood pressure medicine.

For kidneys that need even more help, doctors might suggest dialysis (say: dy-al-uh-sis), a process that cleans the blood artificially. A kidney transplant is another possibility. In this operation, doctors replace a kidney that doesn't work with a healthy kidney donated by another person.

What's Life Like for Kids With Kidney Problems?

Kids who have kidney problems are just like other kids, but they may have to take special medicine or go to the hospital for treatments, such as dialysis. They also will need to talk with their doctors about participating in sports, but often they can join in the fun. Some kids may need to avoid contact sports, such as football, soccer, or basketball.

Kids with kidney illnesses also may need to talk with a doctor or dietitian about the foods they eat. Some kids won't have to follow any special diet, but others may need to avoid salty foods and limit the amount of fluid they drink. Potassium and protein also may be a concern for someone with a kidney disorder.

It's no fun to be sick, no matter the cause. But the good news for kids with kidney problems is that they can take steps to stay healthier and feel better, with a little help from their families and doctors.

Reviewed by: Laszlo Hopp, MD
Date reviewed: March 2009