What is a kidney stone?

A kidney stone is a solid mass formed from substances in the urine. These substances are normally passed in your urine, but they can become highly concentrated and crystalize when there is not enough urine volume. This is typically a result of inadequate daily fluid intake. These stone-forming substances are:

These and other chemicals are the “waste products” that must exit the body.

Kidney stones usually range in size from as small as a grain of sand or gravel to the size of a chickpea. They can even be as large as golf balls. Smaller stones (those less than the size of a chickpea) can pass through the urinary tract on their own, but can be associated with significant pain. Depending on their size, you may or may not notice these stones. Larger stones can get trapped in the ureters (tubes which drain the urine from the kidney into the bladder). When this happens, the stones keep urine from exiting the body.

Blocking the flow of urine causes severe pain or bleeding. Stones that can’t pass on their own are treated with surgery. This decision is based on the stone size, number of stones/overall amount, locations, and other factors such as shape, type, and patient preference.

Kidney with stones forming in the kidney and traveling down the ureter to the bladder.

Stones forming in the kidney and traveling down the ureter to the bladder. Sometimes the stone is too large to pass and can block the flow of urine.

What are the most common types of kidney stones?

The most common type of kidney stone is a calcium oxalate stone. This type of stone happens when calcium and oxalate join in your urine. It can happen when you have high quantities of oxalate, low amounts of calcium and aren’t drinking enough fluids.

Stones caused by uric acid are also fairly common. These come from a natural substance called purine, which is the byproduct of animal proteins (meat, chicken and fish).

These types of kidney stone run in families, so talk to your healthcare provider about your family history.

How does a kidney stone pass through my urinary tract?

A kidney stone starts out in your kidney. It can stay there and build up for years. Some people may even have kidney stones in their kidney for long period of time without knowing it’s there. Once it leaves the kidney, the stone travels down the ureters towards the bladder. The kidney stone enters the bladder and then exits the body through the urethra. Small stones pass out of the body with your urine. Larger stones can get stuck along the way out of the body and may need treatment by your healthcare provider.

How long does it take to form a kidney stone?

You can actually have a kidney stone for years without knowing it’s there. Stones can slowly form over years. As long as these stones stay in place within the kidney, you won’t feel anything. Pain from a kidney stone typically starts as the stone moves out of the kidney to pass out of the body. Sometimes, a stone can form more quickly — in a few months. This is related to your risk factors and history of kidney stones. Your healthcare provider will discuss all of your risk factors and might do a 24-hour urine test to check how quickly you develop stones.

If I have multiple kidney stones, are they all made of the same substances?

Not all kidney stones are made of the same substances. The materials that make up a kidney stone can vary. You could develop a calcium oxalate stone once and then one made of uric acid another time. This change can happen throughout your life and can be due to things like the treatment you were given for your last stone or other medical conditions.

Who is most likely to experience kidney stones?

Caucasian men in their 30s and 40s have the highest incidence of kidney stones. However, anyone can develop kidney stones.

What are the risk factors for developing kidney stones?

Risks for developing kidney stones include:

There are several risk factors for developing kidney stones. These risks can include:

  • Not drinking enough liquids.
  • Having a diets that leads to increased excretion of any of the substances listed above.Having a family history of kidney stones.
  • Having a blockage in the urinary tract.

Certain medical conditions can also increase your risk of developing a stone because you have higher or lower levels of the substances that make up a kidney stone. These conditions can include:

There are medications that can increase your risk of developing a stone. These medications can include:

  • Diuretics (“water pills”).
  • Calcium-based antacids.
  • Crixivan® (used to treat HIV infections).
  • Topamax® and Dilantin® (used to treat seizures).
  • Cipro® (ciprofloxacin).
  • Ceftriaxone (antibiotics).

Certain foods can also place you at risk of a kidney stone. These foods include:

  • Meats and poultry (foods high in animal proteins).
  • Sodium (diets high in salt).
  • Sugars (fructose, sucrose and corn syrup).

What are the signs and symptoms of kidney stones?

You can actually have a kidney stone in your kidney for years and not know it’s there. However, when it starts to move or becomes very large, you may start to feel a few symptoms. Symptoms of a kidney stone can include:

  • Feeling pain in the lower back or side of body. This pain can start as a dull ache that may come and go. It can become severe and result in a trip to the emergency room.
  • Having nausea and/or vomiting with the pain.
  • Seeing blood in the urine.
  • Feeling pain when urinating.
  • Not being able to urinate.
  • Feeling the need to urinate more often.
  • Experiencing fever/chills.
  • Having urine that smells bad or looks cloudy.

Smaller kidney stones may not cause pain or other symptoms. These small stones pass out of the body in your urine.

Last reviewed by a Cleveland Clinic medical professional on 04/22/2020.


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