The use of CT scans in the emergency department has risen more than four-fold over the past decade, according to a study published online Tuesday in the Annals of Emergency Medicine.

By the study's estimates, nearly one-quarter of the 71.1 million CT scans performed in the United States in 2007 happened in the emergency room.

But while the use of the advanced imaging modality has shot up 330 percent over the past 12 years, hospitalization following the scan shrunk by half over the same period, suggesting emergency room doctors were at least sometimes using the technology to rule out more serious conditions and preventing needless hospital stays.
However, CT use rates in the emergency department continue to rise while the rates of post-CT hospitalizations have stabilized in recent years, wrote the authors, led by Dr. Keith E. Kocher, from the University of Michigan in Ann Arbor.

From 1996 to 2007, the use of CTs in the ER went from 3.2 percent of all admissions to 13.9 percent. In the same period, admission rates for patients who underwent a CT scan fell from 26 percent to 12.1 percent. However, changes in the admission rate leveled off after 2003.

The use of CT rose for all 20 of the most common complaints driving patients to the ER, but growth was highest for abdominal pain, flank pain, chest pain and shortness of breath.

Perhaps unsurprisingly, the oldest patients saw the most dramatic increase in CT scan use in the ER. In 1996, 9.1 percent of patients over 79 had a CT scan in the emergency room. By 2007, 29.1 percent of such patients were getting scanned.

The researchers said many factors have been proposed to explain the growth of CT in the emergency room, such as its greater diagnostic accuracy, the rise of defensive medicine and changes in reimbursements.

But the researchers said their study wasn't designed to explain the increase in use, and they said it was often justified, such as to determine if stroke patients would benefit from clot-busting drugs.

Yet sometimes it's more ambiguous, such as with patients presenting with flank pain. Use of CT with these patients grew from 3.5 percent to 40 percent from 1996 to 2007, even though "it is uncertain whether more frequent ED use of CT for this presentation has clearly proven utility," the researchers said.

In an accompanying editorial, Dr. Robert Wears, of the University of Florida Health Science Center, chalked up the rise of CT in part to emergency physicians' eagerness for certainty.

"The occasional 'near miss,' where one manages a patient without imaging, only to discover later that they had CT-detectable pathology of some sort that could have been detected sooner reinforces the desire for greater certainty," he wrote, according to an American College of Emergency Physicians release.

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