What Do the Kidneys Do?

You might never think much about some parts of your body. Your two kidneys, each about the size of a fist, probably fall into that category. These bean-shaped organs (as in kidney beans, not green beans) are on both sides in the middle of your back just below your ribcage. With about 200 quarts (189 liters) of blood pumping from your heart through the kidneys every day, they do a big job for such small organs.

Think of your kidneys as your body's filtering system. You don't use everything that gets into your body from the food you eat, and waste products from chemical reactions that take place in the body build up in the bloodstream. These waste products flow to the kidneys, which sort out what isn't needed and remove it through miniature filtering units called glomeruli (pronounced: glow-mare-you-lye).

The kidneys maintain the delicate balance of chemicals and water that your body needs. When working well, they hold on to what your body needs and they get rid of what it doesn't need. They send the extra water and other waste as urine (pee) through pencil-sized tubes called ureters (pronounced: yu-ree-turz) to the bladder, a sack that holds the urine until you get rid of it when you urinate.

The kidneys also help to regulate your blood pressure, red blood cell production, and your body's calcium and other mineral levels.

Common Kidney Conditions in Teens

Sometimes, the kidneys aren't able to do their job properly. There are many reasons why. Sometimes the blood doesn't flow to the kidneys as well as it should. Other times the tissues of the kidneys themselves can be damaged. And sometimes the outflow of urine from the kidneys can become blocked and lead to kidney damage.

When a person's kidneys stop working altogether, it's called kidney failure. Someone who has kidney failure can develop a number of health problems because the body is unable to get rid of excess water and waste products.

Other than kidney infections, the two most common kidney conditions among teens are known by similar-sounding names: glomerulonephritis and nephrotic syndrome.

Glomerulonephritis

Glomerulonephritis (pronounced: glow-mare-you-lo-neh-fry-tiss), also called nephritis (pronounced: neh-fry-tiss), is an inflammation of the glomeruli, the kidney's filtering units. Nephritis may be caused by an infection, taking certain drugs or toxic chemicals, or by a reaction by the body's immune system that has damaged the kidneys.

When they are inflamed (swollen and irritated), the kidneys pass protein and red blood cells into the urine. Urine can turn brownish from the blood, almost the color of cola. Sometimes nephritis can cause pain in the side, back, or belly, but most of the time it doesn't.

Doctors aren't always sure what causes a person to get nephritis. Sometimes it follows a bacterial infection, such as a streptococcus (or strep) infection like strep throat. When nephritis comes on quickly as it often does following an infection, doctors refer to it as acute nephritis. Drugs are the most common cause of acute nephritis.

Most people who get nephritis get better. However, if it's not treated, the kidneys can sometimes be damaged or even stop working altogether. (Occasionally, the kidneys may stop working even if the nephritis is treated, but that's not common.)

Nephrotic Syndrome

With nephrotic syndrome, also called nephrosis (pronounced: neh-fro-siss), a person's glomeruli are damaged. Instead of filtering only wastes and excess water out of the blood to become urine, the glomeruli allow a lot of protein to come out of the blood and into the urine. Without sufficient protein in the blood, a person may develop edema (pronounced: ih-dee-muh). Edema is swelling in areas such as the feet and legs and the area around the eyes that is caused by excess fluid buildup in the tissues.

People with nephrotic syndrome may have swollen and puffy eyes, especially upon waking up. By the end of the day, their feet may be swollen and their shoes might not fit. They also will produce much less urine than usual — and what urine is produced may look frothy. Other symptoms of nephrotic syndrome include feeling weak or ill and loss of appetite.

Nephrotic syndrome might develop as a part of another disease, such as lupus, or it can happen in some types of nephritis. But most of the time, doctors don't know exactly what causes it. If nephrotic syndrome is caused by another disease, the doctor will treat that disease, which may reduce the symptoms of nephrotic syndrome.

What Do Doctors Do?

If you have a kidney condition, you'll probably visit a pediatric nephrologist (pronounced: neh-frol-uh-jist), a doctor who specializes in treating kidney diseases. The doctor will ask you about any concerns and symptoms you have, your past health, your family's health, any medications you're taking, any allergies you may have, and other issues. This is called the medical history.

If a kidney condition is suspected, the doctor will want to test your urine and blood to look for evidence of glomerulonephritis or nephrotic syndrome and to check how well your kidneys can do their job overall.

One test commonly used to detect kidney conditions is a renal ultrasound. Like the ultrasound pictures that pregnant women get of their fetuses, a renal ultrasound is a picture of the kidneys that's produced by bouncing sound waves off of them. An ultrasound is safe and painless. The ultrasound picture shows how big the kidney is, its shape, and whether there is anything unusual, such as blockage of the urine flow or swelling.

Sometimes doctors order a test called a renal scan, where a dye is injected into the veins and then pictures are taken that show how blood flows through the kidneys. This tells a doctor whether urine is being produced normally. In another test, called a kidney biopsy, the doctor uses a special needle to remove a tiny piece of the kidney for examination under a microscope.

Treating Glomerulonephritis and Nephrotic Syndrome

If you have nephritis that was caused by an infection, your doctor may prescribe antibiotics. For both glomerulonephritis and nephrotic syndrome, your doctor may give you medicine to help reduce the inflammation. You also might receive medicine for high blood pressure and diuretics (medicines that help your body get rid of extra fluid).

Depending on your particular situation, you might have to go on a special diet that limits how much salt or other things you can eat. You also might need to take other medications to help you recover.

Your doctor might ask you to keep a record of your weight, and to keep track of how much you drink and measure how much urine you pass.

Occasionally, if medications and other treatments don't work, the kidneys can stop working well. They may not clear enough of the body's waste products and excess water from a person's system. When this happens, some people may need to start a procedure called dialysis that uses an artificial filtering system to do the job the kidneys aren't doing well enough.

Eventually, people who need dialysis on a permanent basis may need a kidney from another person. This procedure is called renal (kidney) transplantation. Once a person receives a transplanted kidney, he or she no longer needs dialysis to cleanse the blood of waste products and remove excess water — the donated, healthy kidney takes over the job.

Coping With Kidney Conditions

If you or a friend has a kidney problem, it's not likely to affect what you do together. Glomerulonephritis and nephrotic syndrome are not contagious (you cannot get them from someone else).

Teens who are living with health conditions like kidney problems will still be able to do most things, depending on what restrictions their doctors recommend.

If your friend has a kidney problem, the best thing you can do is what you've always done — be a good friend. Learning about the particular kidney condition can help, too. For example, it can help to know that some medications can cause side effects, such as gaining weight. If you have a friend who's in the hospital or sick at home, visit frequently. You can do a lot to help someone else recover just by being supportive and keeping an upbeat attitude.

Reviewed by: Mary L. Gavin, MD
Date reviewed: September 2012