Kidney stones

Originally Published: April 18, 1995 - Last Updated / Reviewed On: June 15, 2012
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Dear Alice,

I think I am passing Kidney Stones. I have a lot of left sided pain, that are a lot like labor pains (in their timing/frequency). I have been to the hospital twice, they have ruled out UTI or anything else. They sent me home with a strainer, told me to strain my urine, and bring any hard objects to my physician. But, I have having trouble identifying them. WHAT DO KIDNEY STONES LOOK LIKE, AND HOW BIG ARE THEY??

—Pebbles or avalanche?

Dear Pebbles or avalanche,

It is unlikely that you will have to sift through an avalanche of hard objects in your urine to find the kidney stones. Kidney stones appear as little pebbles in their smallest form of 0.2 inches (5 mm) in diameter, and these can be passed relatively easily through the urine. Large stones, when located in the ureter (tube that carries urine from the kidneys to the bladder) or in the junction between the kidney and ureter, need to be surgically removed with general anesthesia, and stones in the lower ureter can be crushed and removed by cystoscopy (putting a viewing machine and crushing device up the urethra into the bladder).

Kidney stones are approximately three times more common in men than women. Stones can be a recurrent problem as about 60% of people treated for stones develop the condition again within seven years. Mild chronic dehydration is thought to play a role in the development of kidney stones, which may account for the increased incidence of kidney stones in the summer when people sweat more and have more concentrated urine. About 20% of kidney stones are called infective stones and are related to chronic infections of the urinary tract. These stones are comprised of calcium, magnesium, and ammonium phosphate and they are associated with a high aluminum content and high alkaline content in the urine, due to present bacteria. Seventy percent of kidney stones are comprised of calcium oxalate and/or phosphate. Oxalate is naturally present in the urine and the salt it forms with calcium has a low solubility (does not dissolve easily), so increased levels of oxalate in the urine lead to stone formation. The other 10% of stones occur for less common reasons.

If you arrive home after a seeing a health care provider and realize that you have additional questions, never hesitate to call back your provider to ask. Wishing you (and your stones) an easy passage!

Alice