The accuracy of pre-appendectomy computed tomography with histopathological correlation: a clinical audit, case discussion and evaluation of the literature.

The increasing use of computed tomography (CT) in acute appendicitis makes recognising the radiological hallmarks of the condition and its mimics vital. The differential diagnosis includes both appendiceal and nonappendiceal pathologies. The correlation between pre-appendectomy CT and post-appendectomy histopathology was audited retrospectively. Cases of clinico-histopathological discrepancy underwent blind peer-review, and possible improvements were discussed in the context of the medical literature. A grade for discrepancy was given based on the RADPEER scoring system, and interesting or discrepant cases were examined more closely to identify targets for education. Of the 199 procedures, 4 appendectomies were negative (histologically normal), 182 were positive (primary appendicitis) and 13 were incidental (another primary process caused inflammation). The positive predictive value for pre-appendectomy CT was 91.5 %, and the negative appendectomy rate was 2 %. There were many secondary pathologies, including neoplasia, tuberculosis and endometriosis. Although no CT reports missed a diagnosis that should be made "almost all of the time" and in 96 % of cases, the second, blinded radiologist agreed with the initial assessment, in 3 cases, a missed diagnosis altered clinical management; 2 were "understandable" misses but 1 was not. In five cases, a discrepancy was "understandable" but clinically insignificant. Overall, in comparison to the medical literature, the degree of clinico-histopathological correlation was good. Although identifying areas for improvement was challenging, after a pictorial review of four cases and a discussion of the medical literature, we present our audit results and some valuable learning points for use in the CT assessment of suspected acute appendicitis.