Negative appendicectomy rates as a quality measure in a regional surgical unit: a retrospective review.

Introduction: Historically, high negative appendicectomy rates (NAR) were acceptable to offset the risks of perforation, previously exceeding 20%. With improved imaging and clinical scoring algorithms, there is growing demand for lower negative appendicectomy rates. The objectives were to (1) establish the NAR in our institution and (2) correlate clinical parameters and imaging modalities with histological findings.

Methods: Patients undergoing an appendicectomy between January 2012 and June 2018 were identified using a prospectively maintained pathology database. Histology findings were cross referenced against our radiology system, and anonymised data was collected for gender, age, WCC, Neutrophil and CRP level.

Results: One thousand one hundred fifty-three patients met the inclusion criteria. Fifty-three percent were males (n = 610), with 81% (n = 933) of histology reports classified as appendicitis. Sixty patients had a histologically normal appendix equating to a 5.2% NAR. If lymphoid hyperplasia, fibrosis and atrophy are included, it equates to a NAR of 14.57%. (p < 0.0001). Sixty-six percent of patients had no pre-operative imaging. CT imaging demonstrated a higher sensitivity (93.33%) and positive predictive value (99.60%) compared to ultrasonography. WCC and CRP are statistically significant in predicting appendicitis (p < 0.0001).

Conclusion: There is no consensus on defining a negative appendicectomy or for imaging modality utilisation. CT imaging is the most sensitive and should be used in cases of diagnostic uncertainty. A standardised algorithm regarding the workup of patients with RIF pain along with a consensus on the use of imaging will further reduce negative appendicectomy rates.