Comparison of US and CT on the effect on negative appendectomy and appendiceal perforation in adolescents and adults: A post-hoc analysis using propensity-score methods.

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.