Understanding Urinary Stones

By Barbara C. Bourassa

True or false: Kidney stones are a man's disease, usually requiring surgery, which results from consuming too much calcium.

In fact, all three parts of this statement are false. Although your chances of suffering from kidney stones is small—only 2 to 4 percent of the general population will get them—it is found equally in men and women, and most small stones pass on their own, meaning they don't require any invasive treatment. What's more, the belief that eating too much calcium can lead to kidney stones is a major misnomer that urologists have spent years trying to dispel.

Kidney stones are small, solid masses of crystals that form in the kidney when urine is very concentrated or acidic. Eighty percent of kidney stones are formed when calcium binds with substances called oxalates to form crystals, says Dr. Timothy Averch, associate professor of urology at the University of Pittsburgh Medical Center. But the belief that eating large amounts of calcium, or even taking calcium supplements, can lead to kidney stones is a myth, he states. "There is a very small group of patients who, if they eat too much calcium, may get stones, but in my 12 years of practice, I have only seen that once or twice," he notes. For women in their 40s, it's much more important to protect their bones than to worry about getting kidney stones, he says.

There are dietary practices, however, that are recommended to patients suffering from kidney stones. The first is to stay hydrated. Although the United States may appear to be a very water-oriented nation, most Americans do not drink enough fluids, Averch notes. The result: more concentrated urine, which is more likely to solidify: "Remember when you made rock candy as a kid? The solution was super saturated with sugar, and it caused crystals to form on the string," he says. "We believe the same principle applies to kidney stones."

Dr. Ken Peters, chairman of the urology department at the William Beaumont Hospital in Royal Oak, Michigan, recommends that women drink enough fluids so that their "urine looks like water."

In addition, a diet high in animal protein, oxalates, or salt may cause the urine to be more concentrated. Oxalates are found in dark-colored liquids, such as beer, coffee, tea, colas, and cranberry juice; dark-colored vegetables, such as beets, rhubarb, beans, blackberries, raspberries, strawberries, Concord grapes, dark leafy greens, oranges, tofu, and sweet potatoes; and foods such as peanut butter and chocolate.

If you are diagnosed with kidney stones, it's important to understand what type you have and what, if anything, can be done to prevent more stones. According to Dr. Peters, once you have a stone, "if you make no changes, you have a 50 percent chance of getting another stone within five years."

For this reason, doctors like Averch advocate a metabolic workup, which includes one or two days of 24-hour urine collection, a detailed food diary, and blood work. "We use this as a screening tool so we can identify the source of the problem, rather than putting on a Band-Aid, such as removing the stone and sending the patient home," he says. Most small stones do not require surgery, as they will pass on their own. Averch says larger stones, however, such as those measuring 3 to 4 centimeters, or very large struvite stones, which can fill the entire kidney, must be removed.

The most common procedure for removing kidney stones is called extra corporeal shock wave lithotripsy (ESWL). This involves breaking up the stones using shock waves. ESWL is used when kidney stones are too large to pass or are growing larger, cause constant pain or bleeding, block the flow of urine, causes a chronic urinary tract infection (UTI), or damages kidney tissue.

Although ESWL is the "number-one stone management procedure done around the country," recent studies indicate the success rate may not be as good as urologists once thought, Averch notes. "On stones measuring less than 1 cm, the success rate is in the 50 percent range," he says.

Another common treatment performed by newly trained urologists is called a ureteroscopy. In this procedure, the urologist inserts a scope up the urethra, into the bladder, and into the ureter, and then uses a miniature basket to remove the stone. A second procedure, called a percutaneous nephrolithotomy, involves making an incision in the back or the side of the abdomen and using a scope to remove the kidney stone.

For more information about kidney stones, ask your primary care physician or medical practitioner, who can refer you to a urologist, or visit http://www.upmc.com/HealthManagement/ManagingYourHealth/HealthReference/Diseases/?chunkiid=11725