Retrospective Evaluation of Acute Appendicitis Incorrectly Diagnosed on CT

ABSTRACT

PURPOSE: The purpose of our study was to retrospectively evaluate the CT images of patients suffering with surgically proven appendicitis to determine the causes of missed diagnoses. MATERIALS AND METHODS: We reviewed the pathology reports of the patients with surgically proven appendicitis from two hospitals during a 3-year period. Thirty-seven such cases with a misdiagnosis were identified and they served as our misdiagnosed group (17 females and 20 males, mean age 58 years, age range 15-68 years). These were cases that were misdiagnosed on preoperative abdominal CT. All 57 patients in the control group (30 females and 27 males, mean age 44 years, age range 21-78 years) had undergone laparotomy for acute appendicitis and they had been correctly diagnosed preoperatively on CT. Two abdominal radiologists evaluated the following items from all 94 CT examinations 1) an abnormal appendix, 2) periappendiceal fat inflammation, 3) pericecal extraluminal fluid, 4) pericecal extraluminal air, 5) appendicolith, 6) cecal wall thickening, 7) small bowel dilatation, and 8) the pericecal fat content. Statistical analysis was performed using a Chi-squared test and Fisher's exact test. RESULTS: Any abnormal appendix was not visualized, even retrospectively, in 27 (73%) of the 37 patients from the misdiagnosed group, whereas it was not visualized in 13 (23%) of the 57 patients in the control group (p=0.001). Of the patients who had been misdiagnosed, inflammation of the pericecal fat was observed in 21 patients (57%) as compared to 50 (88%) patients in the control group (p=0.001). Pericecal fluid and air were noted in 15 (41%) and 9 (24%) patients, respectively, in the misdiagnosed group and in 19 (33%) and 14 (25%) patients, respectively, in the control group, (p=0.477 and p=0.901, respectively). Appendicolith was found in 3 (8%) misdiagnosed subjects and in 10 (18%) of the controls (p=0.001). Focal cecal wall thickening was noted in 14 (38%) misdiagnosed patients and in 28 (49%) control patients (p=0.28). Small bowel dilatation was noted in 5 (14%) and 4 (7%) patients in the misdiagnosed and control groups, respectively (p=0.477). The numbers of patients showing abundant pericecal fat were 3 (8%) in the misdiagnosed group and 25 (44%) in the control group (p=0.001). CONCLUSION: The main causes of missed diagnosis of acute appendicitis on CT are non-visualization of an abnormal appendix and a lower index of suspicion by the radiologist. Knowledge of the aforementioned factors may help to avoid the misdiagnosis of appendicitis and so improve the diagnostic accuracy.