Hypothesis: A single dose of prophylactic antibiotics is as effective as a three dose regime in preventing post-operative complications in paediatric patients with simple appendicitis.

This project will compare patients 16 years and under with simple appendicitis (appendicitis that is not perforated or gangrenous). Patients will be randomly divided into two groups;

• Group one will receive a single pre-operative dose of antibiotics (metronidazole 12.5mg/kg up to 500mg and cefazolin 25mg/kg up to 1g) and two 'doses' of normal saline (placebo) eight and sixteen hours after the initial dose, respectively.
• Group two will receive one pre-operative dose of antibiotics (metronidazole 12.5mg/kg up to 500mg and cefazolin 25mg/kg up to 1g) and two post-operative doses, eight and sixteen hours after the first dose, respectively.

Group allocation will be concealed from the patient and their guardian, the treating surgical team and outcome assessors (triple blinded). A process to rapidly reveal group allocation if required will be in place.

The aim of the study is to determine if a single dose of antibiotics is as effective as three doses in preventing post-operative infection. This will be assessed by comparing:

• Duration of hospital stay from operation until discharge, based on a standardised discharge criteria.
• Development of wound infection or requirement of antibiotics in the six weeks post-operation
• Need for re-admission.

Information will be collected prospectively from each patient's hospital notes and from a follow-up phone call six weeks after the operation.

Inclusion Criteria:

• All patients who have their appendix removed and are found on operation to have 'simple appendicitis' as defined in the Cochrane review[7]. That is an appendix that is non-inflamed, acutely inflamed, phlegmonous, suppurative or mildly inflamed.

Exclusion Criteria:

• Patients who on operation are found to have 'complicated appendicitis' defined as an appendix that is gangrenous or perforated.
• Patients who pre-operatively appear to be acutely septic or for another reason require extended antibiotic therapy.
• Patients who, at operation, are found to have other pathology e.g. Meckel's Diverticulum, Intussusception; requiring surgical or medical intervention.
• Any patient whose guardian does not wish for them to participate in the study.
• Patients who have additional co-morbidities, including diabetes, immuno-suppression, cardiac, renal or liver failure.
• If the child continues to show sign of sepsis, in terms of fever, tachycardia, he/she will be discontinued from the study and be given additional doses of antibiotics, as clinically indicated.