This study evaluates the effects of preoperative delay and antibiotics on perforation rate of appendix while waiting surgery for acute appendicitis. Patients with diagnosed acute appendicitis are randomized into two urgency groups: surgery within 8 hours or surgery within 24 hours. In addition, patients are randomized to either receive antibiotics while waiting or waiting without antibiotics.

Inclusion Criteria:

• Acute appendicitis where surgery is planned. Diagnosis of appendicitis should be verified either by clinical diagnosis with Adult Appendicitis Score >=16 or by diagnostic imaging (CT-scan, MRI or ultrasound) showing appendicitis. All patients with symptoms at least 3 days should undergo diagnostic imaging before inclusion.

Exclusion Criteria:

• Complicated appendicitis according to diagnostic imaging. The following findings indicate complicated appendicitis: extraluminal air or extraluminal fecalith; fluid collection, abscess or phlegmon next to appendix; non-enhancement appendiceal wall on contrast enhanced CT-scan.
• Plasma C-reactive protein >=100
• Fever measured on emergency department over 38.5 degrees Celcius.
• Clinical generalized peritonitis or other reason that indicate immediate surgery
• Pregnancy, pregnancy test is taken from all fertile aged women before randomization
• Allergy to study antibiotics, or anaphylactic reaction after betalactam antibiotic or other contraindication for metronidazole or ongoing antibiotic treatment or patient is carrier of resistant bacteria. (This exclusion criteria are applicable only on randomization into antibiotic treatment arms)
• Missing written informed consent