December 2007

Kidney Punch
By Thomas G. Dolan
Today’s Dietitian
Vol. 9 No. 12 P. 52

Kidney stones can create boulder-sized pain, but there are dietary preventive measures—drinking lemonade, for starters—that can lessen the chances of developing the disorder.

One would think that a disease state in which the preventive measures, as well as the cures, are well-established and workable would be on its way out. But just the opposite is true with kidney stones. What’s more, it’s a rapidly growing problem not only in adults but also in children, where it was once a medical aberration.

Definition of Kidney Stones
“Basically, kidney stones are a deposit of minerals in the kidney,” says Matthew Moreland, DO, MPH, of the Baylor Medical Center in Waxahachie, Tex. “The stones block the ureter, or the long narrow duct that conveys urine from the kidney to the bladder. Sometimes, there’s blood in the urine, and [the stones] can cause a pretty intense pain. I’ve heard some women say the pain is worse than child labor. Typically, stones under 5 millimeters will pass on their own; those 6 millimeters or more won’t.”

Gary Faerber, MD, associate professor of urology at the University of Michigan in Ann Arbor, says people with growing kidney stones “think initially they have a pulled muscle or some-thing that feels like a backache. It gets worse and worse. People can’t find a comfortable position. The pain then starts coming in waves. It can be excruciating. It might seem to get somewhat better, but then it will come again. People feel nauseated and vomit.” Frequent and painful urination can also be a symptom.

Kidney stones are often easy to detect—x-rays and scanning devices do the trick—and a urinalysis can usually uncover an infection by spotting blood in the urine.

In the United States, three quarters of the people afflicted with kidney stones develop the variety called calcium oxalate. Other types of stones contain uric acid related to urinary tract infections, while cystine stones are caused by a genetic abnormality. Studies show that patients who have had kidney stones in the past are at greater risk for getting them again.

Medical options include pain medications and calcium-channel blocking medications. In terms of surgery, extracorporeal shock wave lithotripsy (ESWL) is described by Faerber as “the truly ultimate in noninvasive surgery.” This technique uses sound waves to pulverize the stones into small pieces that can be passed spontaneously. “Probably 60% to 80% of the stones that need to be removed by surgery can be accomplished through lithotripsy,” Faerber says. ESWL has been around since the mid-1980s, but the quality of the machines used for the procedure has improved to the point that little anesthesiology is required. In fact, most patients can be made comfortable with intravenous sedation.

Another treatment option is a ureteroscopy. A miniature scope is passed through the urinary system with a small but powerful helium laser used to break the stones. For patients suffering from large stones, the preferred surgery is percutaneous stone removal, which involves putting a small access tube into the kidney through the back and using a device that breaks up the stone and removes it at the same time.

To avoid developing kidney stones, the scientific community recommends several steps to keep the painful deposits at bay, including the following:

• Drink plenty of water. Staying hydrated keeps waste flowing through the body’s system and allows it to exit through urination. Drinking plenty of water—experts suggest eight glasses per day—is especially important during the summer when kidney stones are more apt to develop. Those who live in hot climates and may be used to the heat should be particularly conscious that they are getting enough water.

“Also, the timing of drinking the water is important,” says Faerber. “If you’re going to be outside, drink a glass of water before and afterward. And drink a glass or so before you go to bed. Sleep can be a fasting state when crystalization can occur in the urine. If you’re not getting up at least once a night to urinate, you’re not drinking enough fluids.”

• Not all fluids are created equal. Coffee, iced tea, and colas contain caffeine, which can cause dehydration. Colas especially contribute to the buildup of calcium oxalate.

• Drink lemonade. “We treat people with uric acid stones with lemons, which have the highest concentration of citrate,” says Faerber, who recommends adding 2 to 3 tablespoons of lemon juice to an 8-ounce glass of water. “However, if you want to make a potent lemonade, there’s no reason you can’t squeeze a half a lemon into a glass of water,” he says.

• Meat, fish, and poultry increase the amount of acid in your urine. Cutting meat intake by 30% and eating a vegetarian diet twice per week can help decrease the chances of developing kidney stones, according to Faerber.

• Shake the salt habit. Most salt intake comes not from the salt shaker but rather prepared foods, especially fast foods. Faerber and Moreland suggest that if you’re eating fast food more than twice per week, you’re probably getting too much salt.

Other Foods
What about nutritious foods that can contribute to kidney stones? Chocolate, which may not always be considered a healthy option, contains large amounts of oxalate, as do rhubarb, strawberries, spinach, nuts, and grape juice. However, the general consensus is that the nutritional value of these foods is enough to offset any concerns regarding kidney stones.

On the plus side, some studies have shown that calcium-rich foods reduce kidney stone formation. And even though calcium supplements in some studies appear to contribute to a slight rise in stone incidents, there are more important factors to be considered. Faerber says women concerned about osteoporosis should not restrict their calcium intake for fear of kidney stones.

Living Proof
Diet can make a difference. According to a University of Michigan Health System press release, Sharon Bidwell, who first realized she had kidney stones six years ago, was treated with antibiotics and pain medication before ultimately having a lithotripsy.

Not wanting to go through that experience again, Bidwell, 58, changed her diet, especially her intake of fluids. “I have cut back extremely on cola. I would drink five or six cans a day. I’m down to one can of soda pop a day, and I have tried to increase the amount of water that I [drink],” she says in the release. “I really want to try to avoid having kidney stones again because they’re so painful, and it takes so long for them to pass. It’s just not worth not trying harder.”

In addition to diet considerations, Faerber says one of the main reasons for increasing kidney stone rates in the United States is that the population tends to be sedentary, leading to more people becoming overweight.

Faerber cites a recent report in The Journal of the American Medical Association that suggests a strong association between weight and the incidence of kidney stones. “There’s almost a linear relationship between the two,” he says. “You can almost draw a line between weight gain and the relative risks of kidney stones.” He adds that some procedures, such as intestinal bypasses and gastric staplings, actually increase the risk of kidney stones.

“For the same reasons obesity is growing in adults, it’s also growing in kids,” Faerber says. “Obesity in children is becoming truly an epidemic. This is leading to a growing increase in kidney stones in children as well.”

Profile Shifts
“It is very important for people to be aware of how to prevent kidney stones because many people—about 13% of men and 7% of women—will have kidney stones sometime in their lives,” Faerber says.

At first glance, it may appear that those numbers are not very alarming. In the context of the medical options available and the simplicity of preventive measures, it would seem kidney stones should be a decreasing phenomenon. However, the opposite appears to be true.

“One of the biggest news items in this area is that, in the past, kidney stones were thought to be a disease mainly of males,” Faerber says. “When I started practicing 20 years ago, the ratio was three males had kidney stones to every one female. Now the ratio is closer to 1.5 to 1. I suspect that in the next 10 years, the ratio will be about equal. Women are rapidly catching up with us, and, for better or worse, it will keep us urologists in business.”

— Thomas G. Dolan is a medical/business writer based in the Pacific Northwest.

Kidney Stones in Children
“In the past five or so years, there has been an increase of kidney stones in children,” says Yegappan Lakshmanan, MD, FAAP, assistant professor of pediatric urology at Johns Hopkins Hospital in Baltimore. Lakshmanan says the range of children developing the urologic disorder includes premature babies, those who have had long hospital stays, those aged 6 to 10, and preteens. “Because this phenomenon has been uncommon, diagnoses have been delayed,” he says. “Pediatricians need to start thinking more out of the box in this area.”

As for exact numbers, Lakshmanan says statistics are now being gathered. He says although the increase of childhood kidney stones has been unexpected, it is not totally surprising given that the incidence of other conditions, including high blood pressure, type 2 diabetes, and obesity, is also on the rise in these age groups.

But while exact numbers and causes are unknown, Lakshmanan says, “Pediatricians agree that too much salt and too little drinking water in children’s diets are probably the main culprits.” He says children should have the urge to urinate every three hours, otherwise they may not be getting enough water. If a child urinates less than that, it could be a sign of dehydration.

Lakshmanan says school-age children “are getting a double whammy. The availability of bottled water or other drinking water is limited, and children are discouraged from going to the restroom. Schools will have to play a role in making bottled water available, limiting soft drinks, and allowing children to visit the restroom as needed.”

Lakshmanan offers the following tips to help limit a child’s chances of developing kidney stones:

• Consume no more than 2.4 grams of sodium or 6 grams (1 teaspoon) of table salt per day.

• Stay away from salty snacks such as chips and pretzels.

• Avoid processed foods, including smoked and cured meats, as well as sodas and canned products with the highest sodium content.

• Rinse canned foods under water to remove some of the sodium.

• Drink 2 liters (64 ounces) of water per day.

• Limit the intake of sugar-laden juices and sodas, which don’t count as proper hydration.