(Associated Press) -- If you're among the hundreds of thousands of Americans with clogged kidney arteries, you might want to consider trying medicines before rushing into angioplasty to open them up. The pricey procedure is no more effective and carries surprisingly big risks, a study found.

The National Kidney Foundation estimates more than 250,000 Americans have narrowing of the arteries that supply blood to the kidneys. It's usually caused by a buildup of fatty plaque, mostly in folks 50 or older, and can result in high blood pressure and, sometimes, kidney failure. Each year, about one in six patients with the condition dies.

About 16 percent of patients with newly diagnosed blockages in kidney blood vessels undergo angioplasty or, occasionally, more-invasive artery bypass surgery. But rushing to get blood vessels cleaned out could be a dangerous mistake, according to a British study and some experts.

Doctors at several British hospitals and universities compared patients with severe kidney artery blockages who were treated just with medicines with a group that got the same drugs and underwent angioplasty, in which a catheter is threaded through an artery to clear out blockages. The angioplasty group fared no better -- and some of those patients suffered serious complications, including deaths and amputations.

"There really was no benefit," said Dr. Harlan Krumholz, a cardiologist and health outcomes researcher at Yale University. "What's remarkable is that this procedure got so popular and adopted into widespread use before a study like this was conducted to show us what its value might be."

He said doctors believe some treatments have obvious benefits, but recently a series of studies like this one have upended conventional wisdom. That means precious health care dollars are being wasted and patients are enduring unnecessary procedures and risks.

In the study, published in Thursday's New England Journal of Medicine, all the patients were treated with drugs to lower cholesterol, control blood pressure and prevent blood clots.

Nearly 400 only got drugs. Another 335 patients also underwent angioplasty, which is most often done for clogged heart arteries. Nearly all of them had a stent, a tiny metal-mesh scaffold, inserted to keep the kidney artery open.

After an average of about three years, the researchers found the two groups had similar rates of death, heart attack, stroke, heart failure and decline of kidney function leading to a transplant or the start of dialysis. But 20 percent of patients getting angioplasty had a related complication in the first month, including two deaths, three amputations of toes or limbs, five cases of sudden kidney failure and four hospitalizations for internal bleeding.

Overall, patients in the two groups had the same rates of heart and kidney problems and death over the entire study period.

This report "is the first hint" that medication may produce equal results to angioplasty, said Dr. Leslie Spry, a kidney foundation spokesman. He said there's an ongoing U.S. study of the same issue.

The foundation's president, Dr. Bryan Becker, said the patients getting angioplasty may not have fared better because they had blockages in small blood vessels in addition to the blocked large blood vessels feeding the kidneys that were cleared out.

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