Risk Factors Associated With Negative Appendicectomy Rates: A Retrospective Cohort Study

Background: Acute appendicitis (AA) is the most common emergency general surgical condition worldwide. Diagnosis is challenging and incorporates clinical, biochemical and radiological investigations. Our aim was to provide data from routine practice investigating widely utilised diagnostic methods from a single centre within the United Kingdom. Methods: We conducted a retrospective observational cohort study of patients who underwent a laparoscopic appendicectomy for AA between April 2022 and March 2023. AA was defined as the presence of transmural polymorphonuclear leukocytes in histology. Subgroup analysis was performed on paediatric patients. Factors associated with AA were investigated, and the diagnostic utility of biochemical and radiological investigations was examined. Results: A total of 330 appendicectomies were analysed. We found an overall negative appendicectomy rate (NAR) of 38% and 48% in paediatric patients. Independent factors associated with AA on the multivariate analysis included elevated neutrophil counts (>7 x 10(9)/L) (OR 4.04), elevated CRP (>5 mg/L) (OR 3.04) and a radiological diagnosis (OR 8.0). Computerised tomography (CT) and ultrasound had sensitivity/specificity of 98%/47% and 35%/86%, respectively. The positive-predictive values were 85% for CT and 50% for ultrasound, and the negative-predictive values were 86% for CT and 77% for ultrasound. Conclusion: Our study has highlighted the importance of utilising a combination of factors to improve the diagnostic certainty of AA. However, our routine practice data have shown different sensitivities and specificities of imaging in comparison to existing literature, resulting in a high NAR. Further real-world data are needed to understand whether these differences from the existing data are seen in other clinical settings.