Kidney Stones

Overview

A kidney stone is a solid piece of material that forms out of substances in the urine. It may remain in the kidney or break loose and travel down the urinary tract.

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. Smaller stones are more likely to pass all the way out of the body whereas many stones or a larger stone are more likely to get stuck and block the flow of urine. All stones regardless of size can cause significant pain.

At some point in their lives 10 percent of Canadians will have kidney stones. Men are more commonly affected than women. The prevalence of kidney stones rises dramatically as men enter their 40s and continues to rise into their 70s. For women the prevalence of kidney stones peaks in their 50s. Once a person gets more than one stone others are likely to develop.

Causes

Doctors aren't always sure what causes a stone to form. A person with a family history of kidney stones may be more likely to develop stones. Urinary tract infections kidney disorders such as cystic kidney diseases and certain metabolic disorders such as hyperparathyroidism are also linked to stone formation. In addition more than 70 percent of people with a rare hereditary disease called renal tubular acidosis develop kidney stones.

There are four major types of kidney stones:

A calcium stone is the most common. 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 stone may form after an infection in the urinary system. These stones contain magnesium and the waste product ammonia.

A uric 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.

A cystine stone is 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.

Symptoms

You should call a doctor when you have:

  • extreme pain in your back or side that will not go away
  • blood in your urine
  • fever and chills
  • vomiting
  • urine that smells bad looks cloudy or even bloody
  • a burning feeling when you urinate

Treatment

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 including:

Increasing fluid intake

This should be done ONLY in consultation with your doctor as it can be dangerous if you are not passing urine.

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. 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.

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.

Ureteroscope

A ureteroscope 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 or the doctor may destroy it with a device inserted through the ureteroscope.

Prevention

If you've had more than one kidney stone you are likely to form another; so prevention is important.

The Kidney Foundation of Canada suggests that you:

  • Drink a glass of water every hour during the day and whenever you get up at night. Be sure to drink plenty of liquids after meals and exercise.
  • If you have calcium oxalate stones avoid large amounts of dairy products or foods high in oxalate content (such as tea or chocolate). Avoid large doses of Vitamin C (4 grams or more daily) and antacids.
  • If you have uric acid stones reduce the amount of red meat in your diet.

There are also drugs available that will help prevent the formation of some kidney stones. Ask your doctor if these are appropriate for you.

Additional Resources

The Kidney Foundation of Canada