Use of CT scans in the emergency room more than quadrupled over recent decades, with more than one in eight patients getting the tests in 2007, according to a new study.
CT scans gained popularity in all of the most common ER complaints, including symptoms where it's unclear what extra information a scan can provide, researchers said.
In some instances, a well-timed scan can help doctors make an important diagnosis and can save money by determining which patients don't need to stay in the hospital for observation, Dr. Keith Kocher of the University of Michigan in Ann Arbor and colleagues write in Annals of Emergency Medicine.
But another recent study found that doctors rely much more on patient history and a physical exam than the results of CTs done in the ER when making a diagnosis (see Reuters Health story of August 12, 2011.)
The scans also come with a small dose of radiation that's been linked to slightly increased cancer risks many years down the line, and have a price tag of a few hundred dollars each.
"You can't keep increasing your rate of scanning the way we are," Kocher told Reuters Health. "Eventually you're just going to be scanning everybody, and that doesn't make any sense."
"We are definitely doing too many," he added.
Kocher's team used a representative sample of about 370,000 trips to ERs across the U.S. between 1996 and 2007. For each visit, they had information on patients' primary complaint, whether or not they were given a CT scan in the ER, and if they were ultimately admitted to the hospital for further treatment or observation.
In 1996, just over three percent of all trips to the ER included a CT scan.
By 2007, that figure had risen to almost 14 percent, which is about a quarter of the 72 million scans done in the U.S., according to the researchers.
Scans became more common for ER patients with all 20 of the most common complaints, and increased the fastest for stomach, side, and chest pains.
For side pain, those CTs are probably not necessary most of the time, Kocher said. In those cases, doctors are typically looking for a kidney stone to show up on the scan.
"Whether or not you diagnose a kidney stone on a CT scan (or another way, with an ultrasound or just using patient symptoms), it kind of doesn't matter, because ultimately most of the patients are sent home," Kocher said.
In that case, "You have to wonder if the CT scan is getting us any additional worthwhile information."
The new findings bolster earlier work pointing to a rapid growth in new imaging technology.
Kocher said it's hard to make a general rule about when a CT scan is or isn't necessary, because specific details of each case come into play.
Over the course of the study, fewer patients were admitted to the hospital after getting a CT scan. That could mean that the tests helped doctors rule out serious conditions and avoid keeping patients in the hospital, but the study can't prove the two are definitely linked, Kocher said.
"A good portion of the increase I think actually is legitimate," said Dr. Robert Wears, an emergency medicine professor at the University of Florida College of Medicine, Jacksonville, who wrote an editorial accompanying the study. For example, scans that would be ordered when patients are hospitalized are now getting done in the ER instead, he said.
But doctors and patients should both keep in mind that the scans aren't harmless, Kocher added.
"We are probably causing some degree of future cancers in our patients as the result of the scans we are doing today," he said. That's especially a concern for kids and for people who need multiple scans.
Unnecessary testing could also lead doctors to find "something incidental" that probably wouldn't have caused a patient any problems, he said, but leads to more doctor visits and more scans for follow-up.
And doing the scans on people who probably don't need them slows down the ER and delays CTs for patients who do, Wears told Reuters Health.
Taken together, the findings mean ER doctors should consider what extra information they will get out of each CT scan, and whether the risks are worth it, and patients can help with that process, Kocher added.
"Sometimes physicians fall into this trap of feeling like patients expect tests to be done," he explained. "For patients, it's important to understand some of the risk related to CT scans ... (and that) it's okay to have a conversation with your doctor about this."