The optimal treatment strategy for complex appendicitis in the pediatric population

The proportion of patients experiencing any complication within 3 months after inclusion. All complications / events will be recorded and scored according to the Clavien-Dindo scale. The following events will be considered as complications but this list is not exhaustive: - Superficial Site infection: Criteria according to the CDC guidelines - Intra-abdominal abscess: Radiologically confirmed fluid collection containing pus or infected material that is surrounded by inflamed tissue. - Stump leakage / stump appendicitis: Radiologically confirmed intra-abdominal fluid collections after appendectomy / recurrence of disease after appendectomy. - Secondary / Prolonged bowel obstruction (including paralytic ileus): Patient requiring gastro-intestinal decompression with a nasogastric tube. - Anesthesia related complications (such as pneumonia) - Operation / trocar site hernia: Clinically confirmed by a resident or surgeon. - Need for additional surgical or radiological interventions related to primary disease (appendicitis) - Recurrent appendicitis: recurrence of disease within 3 months time after inclusion. - Re-admission for an indication related to appendicitis (such as readmissions for observation of fever and abdominal pain) All complications and their subsequent treatment will be registered.

- Proportion of patients experiencing overall complications during admission (patient-level) - Proportion of patients experiencing overall complications within 30 days (patient-level) - Proportion of patients with a PAA within 3 months after inclusion (patient-level) - Proportion of patients with an SSI within 3 months after inclusion (patient-level) - Proportion of patients with a secondary/prolonged bowel obstruction within 3 months after inclusion (patient-level) - Number of days absent from school, social or sport events within 3 months after inclusion (patient-level) - Number of days absent from work within 3 months after inclusion (parents-level) - Total number of extra visits (not the already scheduled ones) to the outpatient clinic, general practitioner’s office or emergency department for abdominal pain within 3 months after inclusion. - Total length of hospital stay during follow-up period for strategy related treatment or complications. - Level of pain during admission (measured by the validated Visual Analogue Scale) - Pain medication utilization during admission - Proportion of patients not having to undergo appendectomy within 3 months after inclusion (subgroup 2 specifically) - Proportion of patients experiencing recurrent appendicitis within 3 months after inclusion. (subgroup 2 specifically) - Recurrent appendicitis is defined as those patients with a clinical and radiological high suspicion of recurrent appendicitis who undergo an appendectomy and histopathological examination confirms the diagnosis of recurrent appendicitis - Proportion of patients experiencing early failure of initial non-operative treatment. (subgroup 2 specifically) Early failure is defined as all patients that undergo an appendectomy during the antibiotic course (iv or oral) due to persistent complaints, clinical deterioration or faecolith. - Proportion of patients that undergo interval appendectomy within 3 months after inclusion. (subgroup 2 specifically) Interval appendectomy is defined as those patients that undergo an appendectomy with a clinical and radiological low suspicion of recurrent appendicitis. Histopathological examination shows no signs of recurrent appendicitis. - QoL measured by the validated EQ-5d-Youth, EQ-5d-Proxy questionnaire and PedsQL 4.0 at admission, 30 days after inclusion, 3 months after inclusion - Medical, non-medical and indirect costs until 3 months after inclusion of the treatment strategy measured by the Health and Labor Questionnaire (HLQ), Medical Consumption Questionnaire (iMCQ) and Productivity Consumption Questionnaire (iPCQ) and gathered actual health care cost - Patient satisfaction measured by the NET PROMOTOR SCORE and validated Patient Satisfaction Questionnaire (PSQ) at 3 months after inclusion.