The Case Control Study of Acute Appendicitis Undiagnosed by Sonography

Keiichi Kimura, Kouki Ido, Hideki Nagano, Kyotaro Toshimitsu

Department of Surgery, Nagoya Tokushukai General Hospital

In this study, our aim was to identify factors associated with the failure of sonography to diagnose acute appendicitis. During the last five years 245 patients were diagnosed pathologically with acute appendicitis at our institution. Fifteen diagnoses were missed by abdominal sonography (False Negative, FN group). We compared the FN group with the remaining 230 patients (True Positive, TP group), who were correctly diagnosed by sonography. The diameter of the appendix was significantly thicker in the FN group than in the TP group (14.5 mm vs. 9.4 mm, p=0.0045). The proportion of patients with severe appendicitis was significantly higher in the FN group than in the TP group (47% vs. 20%, p=0.017). Preoperatively, however, there were no significant differences in age, sex, body mass index, white blood cell count, C-reactive protein or body temperature. We conclude that intestinal tract gas and the severely disrupted appendix may lead to false negative sonographic diagnoses of acute appendicitis. CT scanning would be valuable when sonography fails to demonstrate the inflamed appendix.

Key words
acute appendicitis, sonographic diagnosis, undetectable appendix by ultrasonography

Reprint requests
Keiichi Kimura Department of Surgery, Nagoya Tokushukai General Hospital
2-28-1 Kozoji-cho, Kasugai City, 478-0013 JAPAN

Accepted
July 22, 1998

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