The Effect of Preoperative Imaging on the Negative Appendicectomy Rate

Background Appendicitis is one of the most common causes of acute abdominal pain and appendicectomy is one of the most frequently performed surgical procedures. The proliferation of radiological imaging has reduced the number of patients who have a normal appendix removed, i.e., a negative appendicectomy. We aimed to assess the effect of preoperative imaging on the negative appendicectomy rate (NAR). Methodology All emergency appendicectomies performed at a district general hospital in the United Kingdom over two separate one-year periods were retrospectively analysed using emergency theatre log books. The timeframes were chosen based on the introduction of a diagnostic pathway to reduce the number of appendicectomies performed on patients later found not to have appendicitis or alternative abnormality, i.e., a negative appendicectomy. This pathway involved a greater emphasis placed on preoperative imaging (CT or ultrasound) for patients with suspected appendicitis. The study excluded any patients who were found to have an alternative pathology during surgery. Information technology databases were used to collect data on patient demographics, date of surgery, histology, and any preoperative imaging that was performed. All histological findings showing acutely inflamed appendices and those positive for malignancy were categorised as positive, whereas all other findings were categorised as negative. Results During our initial data collection period (April 2018 to April 2019), we collected data on 207 patients who underwent an appendicectomy. The NAR was 17%. During our subsequent data collection period (August 2020 to August 2021), we collected data on 184 patients. The NAR was 16%. In our adult population, the NAR decreased from 13% to 9%. Discussion At first glance, the NAR does not seem to have improved. On closer look, all patients over the age of 21 years in our re-audit underwent pr-operative CT, and there was a reduction in the NAR in these patients. The issue arises with younger patients, in whom justifying the radiation associated with a CT scan may be difficult. Although ultrasound does not carry the same radiation risk, previous audits at our trust have that shown its sensitivity and specificity for appendicitis is approximately 60%. We may have to explore alternative imaging modalities such as MRI in the paediatric population or accept the higher NAR.