In patients with CT results positive for appendicitis and benign or atypical clinical findings, a diagnosis of chronic or recurrent appendicitis may be considered, said the results of a study published online May 26 in Radiology.
In their study that investigated the clinical outcomes of patients with a diagnosis of appendicitis following a CT exam in whom treatment was deemed unnecessary after clinical evaluation, co-author Emily M. Webb, MD, an assistant professor of clinical radiology at the University of California, San Francisco, (UCSF) and colleagues noted that the negative appendectomy rate among patients who have undergone preoperative CT has been determined to be in the range of 3-6 percent.
“For the diagnosis of acute appendicitis, CT has high sensitivity and specificity with values in the range of 87–100 percent and 83–100 percent, respectively,” they wrote.
The researchers identified 2,283 patients, consisting of 856 men and 1,427 women with an average age of 46 years for inclusion in their study that had undergone CT because they were suspected of having appendicitis between 2002 and 2007 by way of the RIS at UCSF Medical Center.
After the CT reports were reviewed by one reader, the likelihood of appendicitis was assigned a score on a five-point scale: score 1, definitely absent; score 2, nonvisualized appendix with no secondary signs of inflammation; score 3, equivocal; score 4, probable; and score 5, definitely present.
"We wanted to look at patients with a positive CT scan but atypical clinical symptoms who did not have their appendix immediately removed," Webb explained.
The researchers determined diagnosis of appendicitis via CT a false-positive result if the CT report was classified as probable or definite appendicitis, but the patient was not treated within four days, they wrote. Two readers, who were blinded to patient outcome, supporting clinical data and prospective scan interpretation and scale grade, reviewed cases with false-positive results.
Medical records were reviewed to determine patient outcomes and the authors found that 23 percent of the 2,283 patients had CT findings of probable or definite appendicitis. Of this 23 percent, 3 percent of patients did not receive immediate treatment for appendicitis and 38 percent underwent later appendectomy with proved appendicitis following an average interval of 118 days.
The authors noted that of the 13 patients who did not receive immediate treatment, 54 percent never developed appendicitis throughout the average follow-up period of 583 days. One patient of the 13 presented with a normal appendix at eventual surgery. Moreover, 10 percent of 516 patients were found to have undergone nonsurgical treatment, including antibiotics or percutaneous abscess drainage at follow-up.
“In recent years, surgeons increasingly have used CT as an important adjunct to physical examination in the diagnosis of acute appendicitis,” explained Webb and colleagues, who noted that under certain circumstances, CT could complicate treatment when the imaging results and the findings of the surgeon’s clinical assessment are not in agreement.
"When the appendix is not completely obstructed, it can result in a milder form of appendicitis that is chronic or recurring,” Webb said, noting that acute, chronic and recurrent appendicitis are indistinguishable on CT scans.
"The results of our study confirm that CT is a good diagnostic tool for appendicitis and that surgeons should be wary of dismissing positive CT findings," the study concluded.