A total of 45 studies met the inclusion criteria. Twenty five studies evaluated ultrasonography (n=9,121 patients, range 100 to 1,285), of which 19 were 'good quality' and six were 'fair quality'. Twenty-five studies evaluated computed tomography (CT) scan (n=3,925, range 100 to 525) of which 19 were 'good quality' and six were 'fair quality'.
Ultrasonography: The overall pooled estimates for the diagnostic value of ultrasonography were: sensitivity 83.69% (95% CI 82.26 to 85.03); specificity 95.89% (95% CI 95.38 to 96.35); accuracy 92.23% (95% CI: 91.70, 92.80); positive predictive value 89.75% (95% CI 88.60 to 90.90); negative predictive value 93.20% (95% CI 92.20 to 94.20); positive likelihood ratio 20.38 (95% CI: 18.08, 22.97); and negative likelihood ratio 0.17 (95% CI 0.16 to 0.19).
CT scan: The overall pooled estimates for the diagnostic value of CT scan were: sensitivity 93.44% (95% CI 92.11 to 94.56); specificity 93.33% (95% CI 92.25 to 94.27); accuracy 93.38% (95% CI 92.60 to 94.20); positive predictive value 90.33% (95% CI: 88.90, 91.80); negative predictive value 95.50% (95% CI 94.50 to 96.50); positive likelihood ratio 14.02 (95% CI 12.04 to 16.31); and negative likelihood ratio 0.07 (95% CI 0.06 to 0.09).
Sub-group analyses: For good quality studies (19 studies), CT scan (93.73%, 95% CI 92.30 to 94.91) was a more sensitive diagnostic tool than ultrasonography (86.94%, 95% CI 85.34 to 88.38), with less specificity (CT scan was 94.22%, 95% CI 92.90 to 95.32 versus ultrasonography at 95.82%, 95% CI 95.17 to 96.38). For good quality studies (five studies) comparing CT scan and ultrasonography diagnostic tools in the same population, CT scan (88.35%, 95% CI 84.67 to 91.23) was more sensitive than ultrasonography (75.97%, 95% CI 71.62 to 79.84), with greater specificity (CT scan was 90.35%, 95% CI 86.56 to 93.16 versus ultrasonography at 89.37%, 95% CI 86.22 to 91.87).