Purpose: To retrospectively compare ultrasound (US) and CT as the preoperative first-line imaging modality in terms of negative appendectomy rate (NAR) and appendiceal perforation rate (APR) in adolescents and adults with suspected appendicitis.
Methods: We included 2,030 patients in 11 sites who underwent appendectomy following US (n = 102) or CT (n = 1,928). Propensity-score (PS) adjusted and matched comparisons were conducted. Matching was performed with 1:1 and 1:3 ratios. Secondary analyses were performed by adding appendiceal perforation to PS model.
Results: The unadjusted NAR difference between the unmatched US and CT groups (8% [8/102] versus 3.8% [73/1,928]) was 4.1 percentage points (95% confidence interval, -1.2, -9.3; p = 0.133). The PS adjusted difference was 4.1 percentage points (-1.8, -10.0; p = 0.169). The differences after 1:1 (9% [8/94] versus 5% [5/94]) and 1:3 (9% [8/94] versus 3.0% [8/271]) matching were 3 (-4, -10, p = 0.39) and 5.6 (-0.4, -11.6, p = 0.069) percentage points, respectively. The unadjusted APR difference between the unmatched US and CT groups (22% [22/102] versus 23.8% [459/1,928]) was -2.2 percentage points (-10.4, -6.0; p = 0.59). The PS-adjusted difference was -5.2 percentage points (-13.3, -2.9; p = 0.21). The differences after 1:1 (19% [18/94] versus 24% [23/94]) and 1:3 (19% [18/94] versus 20.7% [56/271]) matching were -5 (-17, -6, p = 0.38) and -1.5 (-10.8, -7.8, p = 0.75) percentage points, respectively.
Conclusions: The use of US instead of CT may increase NAR but does not significantly affect APR. © 2016 Wiley Periodicals, Inc. J Clin Ultrasound 44:401-410, 2016.
Keywords: appendectomy; diagnostic imaging; propensity score; tomography; ultrasonography; x-radiography computed.
© 2016 Wiley Periodicals, Inc.