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Leslie Spry, M.D., FACP

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Got Kidney Stones? You're in Good Company

Posted: 06/06/2012 5:43 pm

Kidney stones are one of the most common maladies to befall men, but lately women have been catching up. Over the past two decades, the incidence of kidney stones has doubled in both men and women -- more than 10 percent of men and 7 percent of women in the U.S. have had a kidney stone.

Your Diet is Likely the Culprit

In that time, we have learned much about the cause of kidney stones, and diet is the most important factor. What we eat will dictate what will ultimately pass into the urine and the concentration of these various chemicals becomes important in stone formation. A simple way to think about this is to imagine a glass of iced tea. We can add sugar to the tea up to a certain amount and the sugar will stay in the solution. At a certain point, if we keep adding sugar to the tea, we will see the sugar come out of solution and begin to appear in the bottom of the glass. This is exactly what happens in the urine. However, in the urine there are numerous chemicals that all interact with one another. As the concentration of these chemicals increases, some people begin to form stones. The most common chemical seen in stones is calcium. Calcium comes out of solution because of a number of factors, but the most important is the sodium, not the calcium, concentration in the urine. Hence, the more salt or sodium that you consume in your diet, the more likely calcium stones will form. As you eat salt, you increase your risk of forming a calcium-containing kidney stone.

The Reduced Dairy Myth

The known risk factors for forming calcium stones are high-salt diet, obesity, male sex, family history, a history of prior stone passage, a higher intake of animal proteins, low water intake and a low-calcium diet. Note that a diet that is low in calcium actually increases the incidence of kidney stones. Hence, the old recommendation to follow a reduced-dairy diet after a kidney stone is not true. I believe that the best diet for someone with calcium oxalate kidney stones is the Dietary Approaches to Stop Hypertension (DASH) diet. The DASH diet emphasizes a low salt intake with an increase in the amount of potassium in the diet. The DASH diet recommends around 2,000 milligrams of sodium intake per day, and encourages increased fruit and vegetable intake in the diet with a decrease in the amount of animal proteins in the diet. It is not a vegetarian diet, but rather recommends an increase in fruits and vegetables and a decrease in certain animal proteins. It also recommends the increased consumption of low-fat dairy products.

Recent fad weight-loss diets that are high in protein and low in carbohydrates are known to increase the stone-forming potential in the urine. Patients with known history of kidney stones should avoid such diets.

Water Can Wash Those Stones Away

The other important factor in preventing kidney stones is to increase water intake. Return to my iced tea example. One way to bring the sugar back into solution and off of the bottom of the glass is to add more water. This is exactly what you do to decrease the risk of kidney stones. You should increase your water intake to the point where you are forced to get up at night and pass urine. As you get up at night, drink a glass of water in the middle of the night. This will make your urine more diluted at all times and decrease the risk of forming kidney stones at night when your urine is typically the most concentrated. I am frequently asked, "How much water should I drink to prevent kidney stones?" There has never been a study to test exactly how much water to drink, but if you keep your urine diluted all of the time, you will never give the stones a chance to form. So, the answer is, keep drinking until you quit forming kidney stones and especially keep your urine from getting so concentrated at night or while you sleep.

Kidney Stones Come in All Types

There are other kinds of stones besides calcium stones. Stones may be made up of uric acid (so-called gout stones), struvite (infection stones), cystine, and drug stones. Each of these stones has a different treatment, but the essentials of the basic treatment of all kidney stones are to drink lots of water and follow a DASH diet. In order to treat kidney stones effectively, one must make a specific diagnosis as to the cause of the stones and this will lead to specific treatment. Treatment might include medication, but in all cases water intake and a DASH diet are recommended. If you pass a stone, try to collect the stone for analysis, as this will be very important in the diagnosis of your kidney stone disease.

Kidney stones are treated by primary care physicians, urologists and nephrologists. A urologist is a surgeon who will remove stones that have already formed. Shock-wave lithotripsy is commonly done to break up stones and allow them to pass. If you have recurrent kidney stones, you will require further testing to make a proper diagnosis. This will lead to proper treatment and help prevent future stones from occurring. Visit the National Kidney Foundation for more information.

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