A kidney stone is a solid piece of material that forms in the kidney from substances in the urine. It may be as small as a grain of sand or as large as a pearl.

Most kidney stones pass out of the body without help from a doctor. But sometimes a stone will not go away.

It may get stuck in the urinary tract, block the flow of urine, and cause great pain.

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The following may be signs of kidney stones that need a doctor’s help:

• Extreme pain in your back or side that will not go away

• Blood in your urine

• Fever and chills

• Vomiting

• Urine that smells bad or looks cloudy

• A burning feeling when you urinate

Your doctor will diagnose a kidney stone with urine, blood, and imaging tests.

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If you have a stone that won’t pass on its own, you may need treatment.

It can be done with shock waves; with a scope inserted through the tube that carries urine out of the body, called the urethra; or with surgery.