Radiology: Negative appendectomies decrease as CT usage increases

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The number of appendectomies and the negative appendectomy rate in patients who presented to the emergency department saw significant reductions during an 18-year period, which is associated with increased use of preoperative abdominal CT, according to a study published in the June edition of Radiology.

“Appendicitis is one of the most common causes of abdominal pain in emergency departments, however, its diagnosis remains challenging,” noted Ali S. Raja, MD, MBA, from the Center for Evidence Based Imaging and the department of emergency medicine at Brigham and Women’s Hospital, Harvard Medical School in Boston, and lead study author.

The study was designed to estimate the correlation between the negative appendectomy rate and the rate of preoperative CT in emergency department patients suspected of having acute appendicitis presenting to the emergency department.

Researchers retrospectively reviewed the medical records of all emergency department patients who underwent an appendectomy for suspected acute appendicitis in five-year periods between January 1990 and December 1994 and between March 2003 and February 2008 at the single-site hospital. The researchers chose the first observation period because CT had not become commonly used for appendicitis evaluation at the study site at the time.

Raja and colleagues included negative appendectomy rates, the proportion of appendectomy patients who underwent preoperative CT and the annual number of appendectomies performed as outcome measures for their study.

During the first study period, 971 appendectomies were performed in patients presenting in the emergency room, compared to 637 appendectomies performed during the second study period after CT had been more routinely employed. From 1990 to 2007, the negative appendectomy rate was found to have decreased significantly from 23 percent to 1.7 percent, and the annual number of appendectomies also decreased significantly, from 217 per year to 119 per year, the researchers found. At the same time, the proportion of patients undergoing appendectomy who underwent preoperative CT increased significantly from 1 percent to 97.5 percent.

“One explanation for the significant decreases in both the negative appendectomy rate and the number of appendectomies performed might be that the increased use of imaging has led to a decrease in the number of unnecessary appendectomies, which would support earlier results,” wrote the authors. “We also found that nearly all emergency department patients currently undergoing appendectomy at our hospital undergo preoperative CT.”

The study reported an overall 93 percent reduction in the negative appendectomy rate during the 18-year period, and this finding may be applied to other institutions as CT is increasing becoming the imaging modality of choice for patients suspected of having appendicitis.