Lymphocyte depression as a predictor of postoperative intraabdominal abscess after appendectomy in children

Background This study evaluated the efficacy of lymphopenia to predict postappendectomy intraabdominal abscess (IAA) in pediatric complex appendicitis. Methods This single-center retrospective cohort study included appendectomy patients with complex appendicitis from 4/2012 to 10/2014. IAA was diagnosed based on imaging or undergoing a drainage procedure. Labs were used from the closest day prior to abscess diagnosis or day of discharge from index admission. Lymphocyte percentage was categorized based on age-specific cutoffs with lymphopenia defined as a low percentage. Comparisons were made using chi-square or Fisher exact tests for categorical variables and Mann–Whitney U-tests for continuous variables. Results Of 611 appendectomy patients with complicated appendicitis, 551 had WBC and differential. IAA was identified in 79 (12.9%) patients. There were no significant differences in demographics between IAA and non-IAA groups. Patients with IAA had higher rates of leukocytosis (44.3% versus 12.3%, p < 0.001) and higher rates of age-based lymphopenia (84% vs. 46%, p < 0.001). IAA was independently associated with leukocytosis (OR 3.65, p < 0.001) and lymphopenia (OR 4.46, p < 0.001). Patients with leukocytosis and lymphopenia had the highest abscess rate (36%), and those with normal labs had the lowest (3%, p < 0.001). Conclusions Lymphocyte depression is a useful adjunct to predict postoperative IAA in patients with complicated appendicitis.