Differentiating between simple and complex appendicitis in children

Nowadays appendicitis can be classified into two distinct forms: simple and complex appendicitis. While complex appendicitis often requires immediate surgery, a non-operative treatment seems safe and feasible in simple appendicitis and this is underlined by a bridging chapter in this dissertation. Adequate differentiation between both types is therefore essential, especially to prevent unnecessary surgery in children, but remains challenging. In order to further evaluate this, part I of this dissertation primarily focuses on the identification and assessment of potential clinical prediction rules to differentiate between children with simple and complex appendicitis. Secondarily, it evaluates epidemiological trends of both types and investigates potential positive correlations with common viral pathogens in the Netherlands. Part II of this dissertation focuses on the appendiceal microbial composition and immunological pathways in simple and complex appendicitis in children, as a critical link between the immunological function of the appendix and its microbiota has been previously suggested. In addition, this part investigates whether swabs evaluating the rectal microbial composition can be used as a diagnostic tool to differentiate between simple and complex appendicitis in children. At last, in part III of this dissertation the focus shifts towards the frailest population of children with appendicitis, young infants and especially newborns. This part provides updated insights in the associated risk of mortality and morbidity of appendicitis in newborns and infants up to three months of age, and evaluates the clinical presentation, as diagnosing appendicitis is often challenging.