Kidney stone analysis

A kidney stone analysis is done to:

• Find the chemical makeup of a kidney stone.
• Guide treatment for a kidney stone.
• Give information on how to prevent more kidney stones from forming.

Straining the first urine specimen of the morning is important. That's because a stone may pass into your bladder during the night.

Look carefully at the strainer for a kidney stone. It may look like a grain of sand or a small piece of gravel. Any stone you find should be kept dry—do not put it in fluid or urine. Put it in a cup with a lid or in a plastic bag. Take it to the doctor's office or lab for analysis. Do not put tape on the kidney stone. Tape can change the test results.

The kidney stone you take to the lab will be cleaned of any blood or tissue and then looked at to find what chemicals it is made of.

If you think you might have a kidney stone, talk to your doctor. You may be told to collect the stone by straining your urine through a fine-mesh strainer or through fine gauze. Your doctor may give you a kidney stone strainer, or you may buy one from a drugstore.

Knowing the type of kidney stone helps guide the best treatment choice. Your doctor will talk with you about treatment and prevention measures.

• About 80% of kidney stones are made of calcium oxalate, calcium phosphate, or a combination of both.
• About 10% to 15% of kidney stones are made of magnesium ammonium phosphate (struvite).
• About 5% to 10% of kidney stones are made of uric acid.
• Less than 1% of kidney stones are made of a chemical called cystine.