This review concluded that use of preoperative abdominal computed tomography was associated with lower negative appendectomy rates. The authors' conclusions are supported by the results, but should be interpreted with caution due to the possibility of missing studies, unclear quality of the included studies and limitations with the analysis.

To evaluate the impact of abdominal computed tomography (CT) on the clinical outcomes of patients who presented with suspected appendicitis.

MEDLINE, EMBASE and The Cochrane Library were searched from 1980 to May 2007. Search terms were reported. Reference lists of retrieved studies were screened.

Studies that compared patients who presented with acute right lower quadrant pain and underwent preoperative CT with those who underwent clinical examination alone were eligible for inclusion if they assessed at least one of the clinical outcomes of negative appendectomy rate (as determined by the formal pathology report), perforation rate (as determined by the formal pathology report) and time from presentation in the emergency department to the operating room. Studies that included mainly paediatric patients (<18 years), case-series and case-control studies were excluded.

Included studies were randomised controlled trials (RCTs), cohort studies and historical comparisons. The mean age of included patients ranged from 16 to 43 years. The proportion of men ranged from 40% to 66%. Where reported, CT technique was abdominal/pelvic, abdominal alone or focused appendiceal. The contrast agent used in the controlled studies included intravenous and/or oral contrast. Some studies compared mandatory with selective CT scanning rather than CT or clinical evaluation alone.

Two reviewers independently selected studies for inclusion.

Study quality was not formally assessed.

Two reviewers independently extracted data to calculate odds ratios (ORs) or mean differences, with 95% confidence intervals. Disagreements were resolved through consensus. Authors were contacted to obtain additional unpublished data.

Summary odds ratios together with 95% CIs were estimated using random-effects models. A sensitivity analysis was conducted to examine the effects of omitting individual studies from the meta-analysis. Heterogeneity was assessed using the I² statistic and Q test. Results were stratified according to whether studies compared rates between pre- and post-CT eras and whether studies directly compared results in patients who did or did not receive a CT scan. Sensitivity analysis was conducted by investigating the influence of removing the most heterogenous studies from the meta-analyses.

Twenty-eight studies (9,330 participants) were included: two RCTs, 15 cohort studies and 11 studies that compared historical data collected before the widespread use of CT against data collected after the introduction of CT.

Negative appendectomy rates (10 pre/post CT comparisons, 20 CT/no CT comparisons): Incidence of negative appendectomy was significantly reduced after the introduction of CT (OR 0.52, 95% CI 0.36 to 0.76, I²=70%) and was also significantly lower in patients who received a CT scan compared to those who received clinical evaluation alone (OR 0.57, 95% CI 0.45 to 0.72, I²=32%). Removal of the historical comparison trial responsible for most of the heterogeneity had little influence on the summary estimate and heterogeneity remained.

Time to operating room (10 CT/no CT comparisons): Five studies reported a significantly longer time to operating room among patients who received CT. The mean waiting time was 7.8 hours for the clinical evaluation group and 13.3 hours for the CT group. Standard deviations were not reported.

Perforation rates (seven pre/post CT comparisons, eight CT/no CT comparisons): There was no significant difference in perforation rate between the pre-CT and CT era patients (p=0.74) or in patients who did or did not receive CT (p=0.15). There was no evidence of statistical heterogeneity (p=0.56 and 0.07).

This meta-analysis supported the hypothesis that use of preoperative abdominal CT was associated with lower negative appendectomy rates. Use of CT in the absence of an expedited imaging protocol may delay surgery, but this delay was not associated with increased appendiceal perforation rates.

The review addressed a clear question and inclusion criteria were defined. The literature search was adequate, but no specific attempts were taken to locate unpublished studies and it was unclear whether any language restrictions were applied. Appropriate steps were taken to minimise bias and errors when selecting studies and extracting data. Study quality was not formally assessed and only limited study details were reported and so the reliability of the included studies was unclear. The methods used to pool data were appropriate, although pooling studies with such differing designs was questionable.

The authors' conclusions are supported by the results but should be interpreted with caution due to the possibility of missing studies, unclear quality of the included studies and limitations with the analysis.

Practice: The authors stated that routine CT in all patients who presented with suspected appendicitis could reduce the rate of unnecessary surgery without increasing morbidity. The poorly defined risks of CT-related radiation must be considered and integrated into this clinical decision.

Research: The authors stated that further directions of study include the development and prospective evaluation of an expedited imaging protocol with interdepartmental co-operation among the departments of surgery, radiology and emergency medicine.

Not stated.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.