To describe the type and quality of care being delivered to children (aged 1 - 16 years old) undergoing emergency abdominal surgery in the United Kingdom by measuring baseline compliance against evidence-based recommendations and identifying variations in care between individual hospitals.

The Children's Acute Surgical Abdomen Programme (CASAP) is a prospective national observational cohort study which aims to characterise the type and quality of care being delivered to children having emergency abdominal surgery.

The investigators aim to recruit every U.K. hospital undertaking this type of surgery in children, and capture information on 5000 patients over the study period.

The data collected will include information on patient risk factors, compliance with process quality indicators and the incidence and type of postoperative complications encountered. The data collected will be used to describe the current epidemiology of this patient group and to develop and internally validate a risk prediction tool for children undergoing emergency abdominal surgery. This tool be used to provide hospitals with their own risk-adjusted outcome measures and can subsequently be used to inform bedside decision-making. Patients will be followed up for 10 years through a data linkage process with National Health Service (NHS) Digital national databases.

Inclusion Criteria:

• Children aged 12 months and 16 years old
• Children undergoing unplanned abdominal surgery, where the preoperative diagnosis was considered to be related to a non-traumatic bowel (including appendix), hepatobiliary, and/or splenic pathology.

(Definitions - Unplanned is defined as non-elective (i.e. the patient presented requiring emergency or urgent intervention, either as a primary presentation or as a complication of previous surgery). Surgery is defined as a procedure undertaken by a surgeon in an operating theatre requiring the support of an anaesthetist. Any surgical approach (e.g. open, laparoscopic, robotic assisted etc) is acceptable.)

Exclusion Criteria:

• Patients / parents who do not provide consent.
• Children <12 months old on day of surgery
• Elective procedures
• Operations where the preoperative indication for surgery was considered to be traumatic, urological or gynaecological in origin
• Organ transplants
• Insertion/removal of dialysis catheters
• Interventional radiology procedures
• Caesarean sections
• Herniotomies, if the procedure does not involve access to the intra-abdominal cavity.

Children aged 1 - 16 years old undergoing emergency abdominal surgery.

There is no plan to share individual participant data with other researchers.