CT following US for possible appendicitis: anatomic coverage

Abstract

Objective: To determine superior-inferior anatomic borders for CT following inconclusive/nondiagnostic US for possible appendicitis. Methods: Ninety-nine patients with possible appendicitis and inconclusive/nondiagnostic US followed by CT were included in this retrospective study. Two radiologists reviewed CT images and determined superior-inferior anatomic borders required to diagnose or exclude appendicitis and diagnose alternative causes. This “targeted” coverage was used to estimate potential reduction in anatomic coverage compared to standard abdominal/pelvic CT. Results: The study group included 83 women and 16 men; mean age 32 (median, 29; range 18-73) years. Final diagnoses were: nonspecific abdominal pain 50/99 (51 %), appendicitis 26/99 (26 %), gynaecological 12/99 (12 %), gastrointestinal 9/99 (10 %), and musculoskeletal 2/99 (2 %). Median dose-length product for standard CT was 890.0 (range, 306.3 – 2493.9) mGy.cm. To confidently diagnose/exclude appendicitis or identify alternative diagnoses, maximum superior-inferior anatomic CT coverage was the superior border of L2-superior border of pubic symphysis, for both reviewers. Targeted CT would reduce anatomic coverage by 30-55 % (mean 39 %, median 40 %) compared to standard CT. Conclusions: When CT is performed for appendicitis following inconclusive/nondiagnostic US, targeted CT from the superior border of L2-superior border of pubic symphysis can be used resulting in significant reduction in exposure to ionizing radiation compared to standard CT. Key Points: • When CT is used following inconclusive/ nondiagnostic ultrasound, anatomic coverage can be reduced. • CT from L2 to pubic symphysis can be used to diagnose/exclude appendicitis. • Reduced anatomic coverage for CT results in reduced exposure to ionizing radiation.