The APPSYPP trial is a randomized national multicenter feasibility superiority pilot study comparing appendectomy with symptomatic treatment in children with imaging-confirmed uncomplicated acute appendicitis. Patients are recruited from all five Finnish university hospitals. Inclusion criteria are: 1) age 7-15 years, 2) imaging-confirmed uncomplicated acute appendicitis (no appendicolith, perforation, abscess, or tumor suspicion), and 3) CRP ≤ 65 mg/l. Patients are randomized to receive emergency appendectomy or symptomatic treatment. In the surgery group, patients undergo laparoscopic appendectomy within 18 hours after randomization. In order to ensure patient safety, symptomatically treated patients are hospitalized for at least 24 hours, and receive intravenous fluids and analgesics according to standard clinical practice. Primary outcome is treatment success at 30 days defined by not fulfilling any of the treatment failure criteria. In the surgery group, treatment failure is defined as normal appendiceal histopathology or any postintervention complication requiring general anesthesia. In the symptomatic treatment group, treatment failure is defined as inability to discharge from hospital without appendectomy within 48 hours after randomization with a finding of histopathologically inflamed appendix, appendectomy during the initial hospital stay due to clinical progression of appendicitis with histopathologically and surgically confirmed complicated acute appendicitis, appendectomy with a histopathological finding of acute appendicitis after hospital discharge, or any complication of appendicitis requiring general anesthesia. Predefined secondary outcomes include later appendectomies, recurrence of histopathologically confirmed appendicitis and associated symptoms, postintervention complications, return to normal daily activities, quality of, resolution of appendicitis in US imagining after 1 month of symptomatic treatment, comparison of US and MRI findings at presentation, and differences in serum biomarkers and fecal microbiota composition.