- The Washington Times - Tuesday, October 2, 2007

The mystery behind how kidney stones are formed may be unraveling.

Recently, researchers have found that calcium oxalate stones originate from the renal papilla on the inner part of the kidneys, says Andrew P. Evan, chancellor professor in cell biology and pathology at Indiana University School of Medicine in Indianapolis. He holds a doctorate in anatomy and pathology.

He has received grant money from the National Institute of Diabetes and Digestive and Kidney Diseases at the National Institutes of Health in Bethesda to study the kidneys at the time of kidney stone removal. About 75 percent of people with kidney stones have calcium oxalate stones that occur without known cause, he says.

“We are getting closer to knowing what that cause is,” Mr. Evan says. “The primary problem we know is that patients have high calcium in the urine. The high calcium in the urine now fits what we see in the papilla. Biologically, it is starting to make very good sense.”

Kidney stones come in many shapes and sizes for many different reasons. Most of the reasons are not completely understood, which makes it hard to find the best ways to treat and prevent the stones.

Sometimes, if the urine calcium and sodium are elevated, limiting sodium in the diet could help reduce the amount of calcium found in the urine, says Dr. Michael Choi, associate professor of medicine and the nephrology fellowship director at Johns Hopkins University School of Medicine.

“Sodium and calcium tend to follow each other,” Dr. Choi says. “If you eat a lot of salt, your kidney knows you don’t need it and you excrete it. Calcium will follow. If you eat a lot of salt and have a high urine calcium, it will make the calcium worse in the urine.”

Patients should have a stone analysis and proper urine and blood tests to determine what type of stones they have, says Dr. S. Reza Ghasemian, urologist and director of transplantation urology and laparoscopic urology at Washington Hospital Center in Northwest.

“If patients think they are passing a stone, they should strain the urine and bring the fragment to the physician for analysis,” Dr. Ghasemian says. “That is the most important piece of information the physician needs.”

Although calcium oxalate stones have calcium in them, restricting calcium in the diet is not usually needed when a patient has this type of stone, he says. In fact, reducing calcium intake may increase the risk of forming stones.

Other types of common kidney stones are calcium phosphate stones, uric acid stones, cystine stones, medication-induced stones and infection-induced stones, says Dr. Fredric Coe, professor of medicine at the University of Chicago. About 12 million Americans will form a kidney stone in their lifetime, he says.

Genetics, too much calcium in the urine, too much oxalate in the urine and low levels of citrate in the urine are some of the identifiable causes of kidney stones.

It would be helpful to know the mechanism behind why kidney stones form, Mr. Evan says. He is studying patients when idiopathic calcium oxalate stones are removed. For the study, he surgically views the papilla and biopsies it. He is trying to identify the initial changes in the area that lead to stone formation and growth.

Because researchers now better understand renal physiology, they will be able to start creating new drugs, he says. Right now, studies show that a group of drugs called thiazides help to prevent patients with calcium oxalate stones from having them reoccur.

Further, many doctors who find calcium oxalate stones in patients’ urine overlook that the stones could be created for two different reasons: high levels of oxalate and high levels of calcium.

“You can’t lump them together,” says Mr. Evan, who also is co-director of the International Kidney Stone Institute in Indianapolis. “You can’t do that. Different mechanisms make the same stones.”

Along with the grant that allows Mr. Evan to study the origin of calcium oxalate stones, he has another grant from the National Institute of Diabetes and Digestive and Kidney Diseases that looks at the methods that urologists use to remove kidney stones, he says.

Specifically, Mr. Evan is studying shock wave lithotripsy, a method of breaking up kidney stones. He is trying to investigate side effects of the procedure, such as how it may damage the kidneys. He would like to develop guidelines to change how doctors run the equipment.

“We’re going to publish a paper real soon that suggests that if you have multiple shock wave treatments that your stones may change from calcium oxalate to calcium phosphate,” Mr. Evan says. “We are trying to do studies to sort out cause and effect. We think it may be the biggest side effect of lithotripsy.”

One of the most technologically advanced procedures to break up kidney stones is laser surgery, says Dr. Thomas Jarrett, professor and chairman of urology at George Washington University Hospital in Northwest.

“A holmium laser can break up any kind of stone, using a fiber less than 1 millimeter in diameter,” Dr. Jarrett says. “They have been evolving for the last 10 to 15 years.”

The prevalence of kidney stone disease is between 10 and 15 percent of the United States’ population, he says.

“There are a lot of things about stones that we don’t know,” he says. “You can take 10 people with the same urine composition. One or two will form stones and others won’t and we don’t know why.”

In the meantime, kidney stone patients need to say “water, water, water,” says Dr. George W. Tawil, president of the medical staff at Inova Alexandria Hospital and urologist in private practice in Alexandria.

“If you keep hydrated, it’s basic physics,” Dr. Tawil says. “If you increase the hydration, whatever you have, calcium or uric acid, whatever, it will flush out.”

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