Kidney Stones

What Do My Kidneys Do?

Your kidneys are bean-shaped organs, each about the size of your fist. They are located near the middle of your back, just below the rib cage. The kidneys are sophisticated trash collectors. Every day, your kidneys process about 200 quarts of blood to sift out about 2 quarts of waste products and extra water. The waste and extra water become urine, which flows to your bladder through tubes called ureters (YOOR-uh-ters). Your bladder (BLAD-ur) stores urine until you go to the bathroom.

Information IconView Supplements for Kidney Stones

Diagram of how the kidneys filter the blood

Wastes removed from the blood go to the bladder.

The wastes in your blood come from the normal breakdown of active muscle and from the food you eat. Your body uses the food for energy and self-repair. After your body has taken what it needs from the food, waste is sent to the blood. If your kidneys did not remove these wastes, the wastes would build up in the blood and damage your body.

In addition to removing wastes, your kidneys help control blood pressure. They also help to make red blood cells and keep your bones strong.

What Is a Kidney Stone?

A kidney stone is a solid piece of material that forms in the kidney out of substances in the urine.

A stone may stay in the kidney or break loose and travel down the urinary tract. A small stone may pass all of the way out of the body without causing too much pain.

A larger stone may get stuck in a ureter, the bladder, or the urethra. A problem stone can block the flow of urine and cause great pain.

Are All Kidney Stones Alike?

No. There are four major types of kidney stones.

  • The most common type of stone contains calcium (KAL-see-um). Calcium is a normal part of a healthy diet.
  • Calcium that is not used by the bones and muscles goes to the kidneys. In most people, the kidneys flush out the extra calcium with the rest of the urine. People who have calcium stones keep the calcium in their kidneys.
  • The calcium that stays behind joins with other waste products to form a stone.
  • A struvite (STROO-vite) stone may form after an infection in the urinary system. These stones contain the mineral magnesium (mag-NEE-zee-um) and the waste product ammonia (uh-MOH-nyuh).
  • A uric (YOOR-ik) acid stone may form when there is too much acid in the urine. If you tend to form uric acid stones, you may need to cut back on the amount of meat you eat.
  • Cystine (SIS-teen) stones are rare. Cystine is one of the building blocks that make up muscles, nerves, and other parts of the body. Cystine can build up in the urine to form a stone. The disease that causes cystine stones runs in families.

What Do Kidney Stones Look Like?

Kidney stones may be as small as a grain of sand or as large as a pearl. Some stones are even as big as golf balls. Stones may be smooth or jagged. They are usually yellow or brown.

Round kidney stone

Golf-ball-sized and brown

Small and smooth kidney stones

Small and smooth

Sharp looking kidney stones

Jagged and yellow

Kidney stones vary in size and shape. These are not actual size.

What Can My Doctor Do About a Problem Stone?

If you have a stone that will not pass by itself, your doctor may need to take steps to get rid of it. In the past, the only way to remove a problem stone was through surgery.

Now, doctors have new ways to remove problem stones. The following pages describe a few of these methods.

Shock Waves

Your doctor can use a machine to send shock waves directly to the kidney stone. The shock waves break a large stone into small stones that will pass through your urinary system with your urine. The method does not require cutting open the body.

Two types of shock wave machines exist. With one machine, you sit in a tub of water. With the other type of machine, you lie on a table.

The full name for this method is extracorporeal (EKS-trah-kor-POR-ee-ul) shock wave lithotripsy (LITH-oh-TRIP-see). Doctors often call it ESWL for short. Lithotripsy is a Greek word that means stone crushing.

Tunnel Surgery

In this method, the doctor makes a small cut into the patient’s back and makes a narrow tunnel through the skin to the stone inside the kidney. With a special instrument that goes through the tunnel, the doctor can find the stone and remove it. The technical name for this method is percutaneous (PER-kyoo-TAY-nee-us) nephrolithotomy (NEF-row-lith-AH-tuh-mee).


A ureteroscope (yoo-REE-ter-uh-scope) looks like a long wire. The doctor inserts it into the patient’s urethra, passes it up through the bladder, and directs it to the ureter where the stone is located. The ureteroscope has a camera that allows the doctor to see the stone. A cage is used to catch the stone and pull it out.

Ask your doctor which method is right for you.

How Will My Doctor Find Out What Kind of Stone I Have?

The best way for your doctor to find out what kind of stone you have is to test the stone itself. If you know that you are passing a stone, try to catch it in a strainer.

Your doctor may ask for a urine sample or take blood to find out what is causing your stones. You may need to collect your urine for a 24-hour period. These tests will help your doctor find ways for you to avoid stones in the future.

Lady using the toilet

Try to catch a stone in a strainer.

What Can I Do To Avoid More Stones?

Drink more water. Try to drink 12 full glasses of water a day. Drinking lots of water helps to flush away the substances that form stones in the kidneys.

You can also drink ginger ale, lemon-lime sodas, and fruit juices. But water is best. Limit your coffee, tea, and cola to one or two cups a day because the caffeine may cause you to lose fluid too quickly.

Your doctor may ask you to eat more of some foods and to cut back on other foods. For example, if you have a uric acid stone, your doctor may ask you to eat less meat, because meat breaks down to make uric acid.

The doctor may give you medicines to prevent calcium and uric acid stones.

Nutrients, Daily Amounts, and Applications

Information IconDietary supplements related to Kidney Stones

  • Magnesium: 300-500 milligrams
  • Potassium: 3,500-4,500 milligrams
  • Vitamin B6: Up to 50 milligrams (including a multivitamin/mineral supplement containing the B-complex vitamins)

Medical Alert

  • No supplement program dissolves kidney stones that have already formed.
  • If you have kidney or heart problems, check with your doctor before taking taking supplemental magnesium.
  • People taking diuretics or who have kidney disease or diabetes should not use potassium supplements without first consulting their doctors.
  • Some doctors recommend taking no more than 50 milligrams of vitamin B6 without medical supervision. Large doses have been associated with nerve damage. Stop taking B6 if you develop numbness in your hands or feet or unsteadiness in walking