Low-Radiation CT Scans Effective at Spotting Appendicitis: Study
Approach cuts cancer risk without raising number of unnecessary surgeries
Wednesday, April 25, 2012
Doctors typically order CT scans of the abdomen for adult and teen patients who have symptoms of appendicitis, such as pain near their belly button, to diagnose their condition before they decide whether to do an appendectomy -- surgery to remove the appendix.
"As long as CT is used judiciously, it allows doctors to reduce the rate of negative appendectomies -- before CT scans, about one in five patients would have their appendix removed and it was normal and their pain was due to something else," explained Dr. Erik Paulson, a radiologist at Duke University Medical Center.
There are about 250,000 cases of appendicitis a year in the United States, according to study background information.
While CT can improve care for people with suspected appendicitis, there are concerns among doctors and patients about exposure to the low levels of radiation during CT scanning and potential increases in cancer risk.
"There is no question that CT is safe, but we believe that we should try to reduce radiation as much as possible, particularly in young adults and children where risk of radiation is highest," Paulson said.
In the current study, published April 26 in the New England Journal of Medicine, researchers compared the rates of appendectomies where the removed appendix that turned out to be normal between patients who had undergone a CT scan either with low or standard doses of radiation.
"We hope our study can contribute to reduction in radiation exposure in the young populations," said study co-author Dr. Kyoung Ho Lee, a radiologist at Seoul National University College of Medicine.
The study involved 891 patients between the ages of 15 and 44 in an urban hospital in South Korea who got CT scans because of suspected appendicitis. The researchers randomly picked 444 of the patients to receive low-dose CT and the remaining 447 got standard-dose CT.
Of the 172 patients diagnosed with appendicitis after low-dose CT who went on to have appendectomies, six people (3.5 percent) did not have appendicitis, while six of the 186 patients (3.2 percent) who got standard-dose CT scans turned out not to have appendicitis.
The researchers found no difference between the rates of negative appendectomies in these two groups, indicating that the low dose of radiation could give CT images that were high-enough quality to allow radiologists to pick out cases of appendicitis.
Other aspects of patient care, such as the time it took to get the patient into surgery and the number of patients who needed a second imaging test, were similar between the two groups.
Patients in the low-dose group received 2 millisieverts of radiation during CT compared with 8 millisieverts in the standard group. A millisievert is a unit of ionizing radiation, and the level varies depending on the type of CT scan.
The researchers estimated that abdominal CT at the standard dose would lead to 63 additional cancers for every 100,000 men and 72 additional cancers for every 100,000 women who received a scan at the age of 30. Their estimates for the lower dose were 14 and 16 cancers, respectively, for every 100,000 men and women at age 30.
However, "it is highly debatable whether the radiation levels used in our two groups can actually induce cancer and whether use of the low dose rather than the standard dose can actually reduce carcinogenic risk," Lee said.
Although the risk of cancer associated with CT scan has not been proven, "if you can get the same result with a lower dose of radiation, that is obviously going to be important because it gives the patient a sense of relief that it is not going to cause cancer in the future," said Dr. Rodney Mason, an associate professor of surgery at the University of Southern California.
It could be time to adopt lower doses, at least for patients between the ages of 15 and 44, Mason said, adding that more studies are needed to know if low-dose CT could be effective in younger and older groups.
Previous studies have looked at smaller groups of patients and found comparable effectiveness with low-dose CT for diagnosing appendicitis.
There are some groups, such as obese people, for whom doctors would probably need to use a relatively higher dose of radiation, Paulson said. The new study involved patients who were thinner on average than in the United States and did not determine if differences existed in effectiveness of low-dose CT in heavier patients.
In general, Paulson and his colleagues at Duke have already been dialing back the radiation dose for CT and seeing the same accuracy for diagnoses of different conditions, he added.
"I think most practices, across the board for all kinds of diseases, could drop the radiation dose by 20 to 30 percent and diagnostic efficacy would be the same," Paulson said.
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