PRESCRIPTIONS
Acting now may prevent kidney stones

By Landis Lum

Q. My husband had a really painful attack of kidney stones last week. How can kidney stones be treated, and how can he prevent another attack?

A. Your husband probably has calcium oxalate stones, the cause in 75 percent of cases. His doctor can do tests to see what kind of stone he has.

For stones that don't pass by themselves, shock-wave lithotripsy may be needed — your husband would be placed in a water bath and ultrasound would be used to create shock waves that travel through the skin and body to hit the stones, breaking them apart into tiny sand-like pieces. But surgical removal may be needed if the stone is very large, in an inaccessible location, or composed of cystine (which can't be shattered by lithotripsy).

Having concentrated urine can cause stones to crystallize.

To prevent future attacks, your husband should drink 10 extra glasses of fluid each day (of which at least half should be water), evenly spaced throughout the day. Include a full glass at bedtime (to prevent concentrated urine overnight while sleeping, even if he may have to awaken at night to urinate).

He should also drink extra fluids after exercise. The urine should look pale and almost watery.

Your husband also should reduce the amount of meat in his diet, and the amount of salt as well. This will reduce the amount of calcium in his urine and will increase urinary citrate (which helps dissolve stones). In fact, in a study published in the New England Journal of Medicine in January, men with calcium oxalate stones who ate a diet low in animal protein and salt had half the number of future kidney stones than men who simply ate a diet low in calcium.

One upshot is that your husband should not reduce the amount of calcium in his diet (doing so may actually increase kidney stones, even in patients who excrete high amounts of calcium in their urine).

Most experts also recommend reducing the amount of oxalate in the diet, even though there aren't any definitive studies showing that high oxalate intake causes stones. So he should avoid spinach (this has the highest oxalate content of any food!), wheat bran (present in cereals such as Fibre One, bran flakes, etc.), rhubarb, chocolate, beets, nuts, peanut butter, tea and strawberries.

Also, he shouldn't take more than 500 milligrams of vitamin C a day because it increases oxalate production.

If he remembers nothing else, just remind him to drink lots of water throughout the day, eat more fruits and vegetables, consume less meats, and avoid salty foods such as pizza, Spam, hot dogs and ramen.

Dr. Landis Lum is a family practice physician with Kaiser Permanente, and an associate clinical professor of family and community medicine at the University of Hawai'i's John A. Burns School of Medicine.

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