In many cases they can be avoided by drinking lots of fluids and changing the diet.
Kidney stones occur when the urine contains too high a concentration of certain substances, usually calcium oxalate or calcium phosphate. These substances clump up, forming stones that, if smaller than a pea, can be passed in the urine, albeit painfully. Larger stones may need to be removed with minimally invasive surgery or a procedure called lithotripsy, which breaks up the stones by shock waves, said Dr. Michael Choi , a kidney specialist at the Johns Hopkins School of Medicine.
Kidney stones caused nearly 3 million visits to doctors and 600,000 trips to the emergency room in 2000 alone, according to the National Institute of Diabetes and Digestive and Kidney Diseases.
Not drinking enough fluid is a major cause, but genetics play a role, too.
While it used to be thought that consuming too much calcium led to kidney stones, it’s now believed that foods high in calcium may actually help prevent kidney stones. If you’ve had a prior kidney stone containing calcium oxalate, though, it may be wise to limit your consumption of foods that contain calcium oxalate, including chocolate, coffee, cola, nuts, rhubarb, spinach, strawberries, tea, and wheat bran.
For calcium kidney stones, it may also help to increase intake of lemon juice — the real kind, not just lemon flavoring. “This keeps calcium from binding in the kidney,” said Dr. Richard Babayan , chief of urology at Boston Medical Center.
If you have uric acid stones, you should increase the alkalinity of the urine. A prescription drug called Urocit-K can do this, helping dissolve these stones, as can over-the-counter preparations of potassium citrate and sodium bicarbonate.
Once you do pass a kidney stone, be sure to catch it — some people use tea strainers — so doctors can figure out what type of stone it is and how you can avoid getting that kind again.