What Are the Kidneys? The kidneys are two bean-shaped organs, each about the size of a fist. They're on both sides in the middle of your back, just below your ribcage. What Do the Kidneys Do? The kidneys have a big job. About 200 quarts (189 liters) of blood pump from your heart through the kidneys every day. Think of your kidneys as your body's filtering system. What our bodies don't use (from the food we eat, and waste products from chemical reactions, etc.) 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 tubes called ureters (pronounced: yu-REE-turz) to the bladder, the sac that holds pee until you get rid of it when you urinate. The kidneys also help to regulate blood pressure, red blood cell production, and the body's calcium and other mineral levels. What Is Kidney Disease? Sometimes, the kidneys don't work as they should. Many things can cause problems, such as when: The blood doesn't flow to the kidneys as well as it should. Tissues of the kidneys are damaged. The outflow of urine from the kidneys gets blocked and causes kidney damage. When a person's kidneys stop working, it's called kidney failure. Someone who has kidney failure can develop a number of health problems because the body can't get rid of excess water and waste products. Older people usually have kidney disease caused by high blood pressure or diabetes. But in kids and teens, kidney disease is usually from: infection or repeated infections structural issues with the way the kidney was built glomerulonephritis nephrotic syndrome Infections Urinary infections happen a lot. They usually start in the bladder, where pee is stored. But they can travel up and infect the kidneys. The infection can create a scar and injure the kidneys. Overtime, scars can affect how well the kidneys work. Structural Problems The kidneys can be too small or their parts may be made in an unusual way. Sometimes pee flows backward, making the kidneys swollen or damaged. Cysts (fluid-filled sacs) can develop in the kidneys and affect how they work. 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. It may be caused by: an infection some drugs or toxic chemicals an immune system reaction that damages the kidneys Sometimes it follows a bacterial infection, such as a strep throat. In some cases, the cause isn't known. Inflamed (swollen and irritated) kidneys pass protein and blood cells into the pee. Pee 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. Most people who get nephritis get better. But sometimes, the kidneys can be damaged or even stop working. Nephrotic Syndrome Nephrotic syndrome, also called nephrosis (pronounced: neh-FRO-siss), is when a person's glomeruli are damaged. Instead of filtering only wastes and excess water into the pee, the glomeruli allow a lot of protein out of the blood and into the pee. Protein usually helps to hold fluid inside the blood vessels. When the protein is lost into the pee, nothing holds the fluid in the blood vessels and it leaks out. A person then gets swollen, especially around the feet, legs, and eyes. Nephrotic syndrome might develop from a disease that affects the kidney or as a part of another disease, such as lupus. But many times, doctors don't know the exact cause. How Is Kidney Disease Diagnosed? If you might 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 medicines you're taking, any allergies you have, and other issues. This is called your medical history . The doctor will want to do urine tests and blood tests to look for signs of structural issues, an infection, glomerulonephritis, or nephrotic syndrome, and to check how well your kidneys are working. One test commonly used to detect kidney conditions is a renal ultrasound. This picture of the kidneys is made using sound waves. It shows how big the kidney is, its shape, and whether there is anything unusual, such as blockage of the urine flow or swelling. An ultrasound is safe and painless. Sometimes doctors order a test called a renal scan. 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 pee is being made normally. In another test, called a kidney biopsy, the doctor uses a special needle to remove a tiny piece of the kidney to check under a microscope. How Is Kidney Disease Treated? How kidney disease is treated depends on the particular problem and what's causing it: Kidney infections are treated with antibiotics . Medicines to decrease inflammation may help with nephritis and nephrotic syndrome. Medicines can treat high blood pressure or help the kidneys make extra pee if fluid or swelling is causing a kidney problem. A person might need to eat a special diet that limits salt or other things. Occasionally, if medicines 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. In that case, a person might need dialysis. This process uses an artificial filtering system to do the job of the kidneys when they can't. Some people who need dialysis on a permanent basis might be candidates for a kidney transplant. This means they get a donated kidney from another person. Someone who gets a transplanted kidney no longer needs dialysis to clean the blood of waste products and remove excess water. The donated, healthy kidney takes over the job. Looking Ahead If you have a kidney condition, you're not alone. The care team is there to help you before, during, and after treatment. It also can help to find a support group. The care team might be able to recommend one in your area. Meeting other teens who are going through the same thing can be a big help. You also can look for online groups and sites, such as: National Kidney Foundation Renal Support Network Back to Articles Related Articles Glomerulonephritis With glomerulonephritis, tiny filtering units in the kidneys stop working properly, causing problems like too much fluid in the body and swelling. Most of the time it can be treated. Find out more. Read More Kidney Stones Kidney stones mostly happen to adults, but sometimes teens can get them. Find out what kidney stones are, how to treat them, and ways to help prevent them. Read More Kidney Transplant If the kidneys stop working, a person will need either dialysis or a transplant. Get the facts on kidney transplant in this article for teens. Read More Dialysis Dialysis is a medical treatment that can take over the job of filtering the blood until a person's failing kidneys heal or are replaced with a kidney transplant. Find out more in this article for teens. Read More Urinary Tract Infections A urinary tract infection (UTI) is one of the most common reasons that teens visit a doctor. Learn about the symptoms of UTIs, how they're treated, and more in this article. Read More Kidneys and Urinary Tract The kidneys perform several functions that are essential to health, the most important of which are to filter blood and produce urine. Read More Hemodialysis Hemodialysis is the type of kidney dialysis that doctors use most to take over the kidneys' job of filtering the blood. Find out more in this article for teens. Read More Peritoneal Dialysis This medical treatment helps people with kidney failure. It can be done at home, often overnight, to take over the kidneys' job of filtering blood. Find out more in this article for teens. Read More Dealing With a Health Condition If you suffer from a chronic illness, you know it can be anything but fun. But you can become better informed and more involved in your care. Here are tips to help you deal. Read More What Problems Can Diabetes Cause? Thinking about your diabetes a little bit now — and taking some steps to prevent problems — can make things easier down the road. Read More Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.