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Acute kidney injuries have more than doubled since 2000, causing nearly 39,000 deaths in 2009 alone, according to a new study.

Severe infections, heart failure, trauma, bad reactions to medicationor surgical complications can all cause sudden declines in kidneyfunction, but it's not yet clear which - or which combinations - ofthese is driving the 10% annual rise.

It's possible, researcherssay, that some newer medications are damaging kidneys, or that pneumoniastrains are getting more dangerous. Or maybe it's simply thattreatments for other diseases, such as sepsis infections and respiratoryfailure, are getting better, while treatment for acute kidney diseaseisn't.

"That would be my guess," says Ramon Bonegio, who studiesacute renal failure at the Boston University School of Medicine and isan attending physician at Boston Medical Center.

There are nodrugs to reduce the incidence or severity of acute kidney injuries,though several are under development, says Bruce Molitoris, president ofthe American Society of Nephrology.

In the new study, publishedThursday in the society's journal, researchers reviewed 1.9 million U.S.hospitalizations due to acute kidney injuries. Only the most seriousinjuries, which required patients to go on dialysis, were counted.

Although acute kidney disease is far more common among AfricanAmericans than whites, the study found that increases were consistentacross races, genders and from middle age up, says Raymond Hsu, a studyauthor and research fellow in the division of nephrology at theUniversity of California-San Francisco.

Molitoris, also aprofessor of medicine at Indiana University, says he was surprised bythe high rate of increase Hsu found but does not doubt his conclusions.

"I think awareness is a big issue," Molitoris says. "It's an under-recognized major complication in the hospital."

Hsu and Molitoris drew a distinction between the acute kidney injuriesthat were the subject of this study and the chronic kidney disease thatcan come with diabetes, hypertension or immune conditions - althoughchronic kidney disease can lead to acute injuries.

With chronickidney disease, which affects a quarter of those over 60, once a patientneeds dialysis, the kidneys have been damaged beyond repair. In acutekidney injury, dialysis is meant to be temporary, until the kidneys canrecover their ability to filter the blood. Nearly one-quarter of thosewith acute kidney injury die before they can be taken off dialysis.

Hsu says the high death rate suggests that dialysis may be overused insome of the sickest patients, who should be given a choice - beforethey're acutely ill - about whether to pursue a painful procedure thatmay do little to extend their lives.

"Would they want thoseinvasive measures?" asks Hsu. "By the time they reach us, they arealready too sick to express those wishes."

Hsu says he next hopesto study patients who do well after an acute kidney infection anddialysis, to better understand their recovery process and translate itto those with worse outcomes.

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