Negative Appendicectomy Rate: Incidence and Predictors

Introduction Acute appendicitis is a common emergency surgical presentation. The gold standard treatment is surgery. Like any surgical procedure, appendicectomy is associated with complications. Negative appendicectomy (NA) can occur, and its incidence is 15%-39%. This study aimed to evaluate the rate and predictors of NA in a cohort. Patients and methods A retrospective study over a year through which data of patients who underwent emergency appendicectomies were collected and analyzed. The absence of inflammatory process and/or other significant pathology in the appendix was considered negative for appendicitis. An utter definition of NA was the absence of inflammatory cells in the appendix. The NA rate (NAR) was calculated using the standard criteria (NAR-SDC) and the strict criteria (NAR-STC). The routine laboratory parameters for diagnosing acute appendicitis on admission were collected. Increased inflammatory markers in the form of leucocytosis of total WBC > 11,000 per mm, elevated CPR > 5 mg/L, and isolated elevated total serum bilirubin > 20 µmol/L, were suggestive of acute appendicitis. Results Three hundred and seventy-two patients were included, 179 males and 193 females with a median age were 27 (5-94) years. The median duration of symptoms and waiting time to surgery were two days and one day, respectively. The mean admission WBC, C-reactive protein (CRP) and serum bilirubin levels were 12,600 (3,000-38,000)/mm(3), 66.9 (1-323) mg/L and 12.7 (4-38) µmol/L respectively. Laparoscopic appendicectomy was performed in 93.5% of patients with a conversion rate of 4.6%. NAR-SDC was 10.2% and NAR-STC was 25.8%. NAR was significantly higher in females than males (39.4% versus 11.1%; p-value 0.0001). Patients with NA were younger (p-value 0.0001), had lower mean total WBC (p-value 0.014), CRP (p-value 0.0001) and total serum bilirubin (p-value 0.0001) levels on admission. Conclusion NA is still a major problem in the management of patients with acute right lower abdominal pain. Our NAR compared favourably with reported rates. Female gender, duration of symptoms more than three days, and lower total WBC were independent predictors of NA.