Table 1 Statements

Statement 1.1 We suggest the use of scoring systems for excluding acute appendicitis in elderly patients with a low-probability score (Conditional recommendation, low quality evidence).

Statement 1.2 We suggest against basing the diagnosis of acute appendicitis in elderly patients only on scoring systems (Conditional recommendation, low quality evidence).

Statement 2 In elderly population, we recommend against basing the diagnosis of acute appendicitis only on patient's clinical signs and symptoms (Strong recommendation, low quality evidence).

Statement 3 We recommend against basing the diagnosis of acute appendicitis in elderly patients only on elevated leukocytes count and CRP value. It should prompt adequate diagnostic course (Strong recommendation, low quality evidence).

Statement 4.1 We recommend the use of CT-scan in all elderly patients with an Alvarado score ≥ 5 to confirm or exclude the diagnosis of acute appendicitis and to distinguish perforated from non-perforated appendicitis (Strong recommendation, low quality evidence).

Statement 4.2 We suggest that elderly patients with an Alvarado score < 5 should be clinically observed and, in case of failure to improve, they could receive abdominal CT with IV contrast (Conditional recommendation, very low-quality evidence).

Statement 4.3 We suggest the use of US in elderly patients with an Alvarado score ≥ 5 who cannot undergo CT scan with IV-contrast (i.e. acute or chronic kidney disease) to confirm the diagnosis of acute appendicitis, but not for excluding it (Conditional recommendation, low quality evidence).

Statement 4.4 We suggest against the use of US for distinguishing perforated from non-perforated appendicitis in elderly patients. [Conditional recommendation, very low-quality evidence].

Statement 4.5 We suggest the use of MRI to confirm or exclude the diagnosis of acute appendicitis and to distinguish perforated from non-perforated appendicitis in elderly patients with an Alvarado score ≥ 5 who cannot undergo CT scan with IV contrast (i.e. acute or chronic kidney disease), if this resource is available. If it is not available, non-contrast CT scan is suggested (Conditional recommendation, very low-quality evidence).

Statement 5 We suggest the application of NOM in selected elderly patients, with evidence of uncomplicated appendicitis at CT-scan and without clinical signs suspected for complicated appendicitis, who wish to avoid surgery and accept the risk of recurrence (Conditional recommendation, low-quality evidence).

Statement 6.1 We suggest the use of NOM with percutaneous drainage (if accessible) in elderly patients with complicated appendicitis with appendicular abscess (Conditional recommendation, low quality evidence).

Statement 6.2 We recommend against the use of NOM in elderly patients with complicated appendicitis with diffuse peritonitis or with a suspected free-perforated appendicitis at CT scan (Strong recommendation, low quality evidence).

Statement 7 We recommend elective colonic screening in all elderly patients with appendicitis (treated both non-operatively and operatively, specially if laparoscopically) (Strong recommendation, very low-quality evidence).

Statement 8 In elderly patients with acute appendicitis, we suggest laparoscopic appendectomy due to a reduced LOS, morbidity and costs (Conditional recommendation, moderate quality evidences).

Statement 9 In elderly patients operated for acute appendicitis, there are no clinical evidences about advantages in the use of linear stapler against other methods (endoloops, clips) for stump closure; we suggest the use of the preferred technique based on local expertise and availability (Conditional recommendation, moderate quality evidences).

Statement 10 In elderly patient, we suggest the positioning of an abdominal drainage in case of complicated (with perforation/abscess/peritonitis) appendicitis (Conditional recommendation, very low-quality evidences).

Statement 11 In elderly patient with acute appendicitis, once operation is indicated, we suggest to perform appendectomy as soon as possible (Conditional recommendation based on very low-quality evidences).

Statement 12 There is no consensus about the removal of a normal appendix with very low quality and indirect evidences; therefore, no recommendation could be made.

Statement 13 We recommend pre-operative broad-spectrum antibiotics in elderly patients undergoing appendectomy for acute appendicitis (Strong recommendation, moderate quality evidences).

Statement 14.1 In elderly patients operated on for uncomplicated acute appendicitis, we suggest to not administrate post-operative antibiotics (Conditional recommendation based on low quality evidences).

Statement 14.2 In elderly patients operated for complicated acute appendicitis, we suggest post-operative broad-spectrum antibiotics (Conditional recommendation based on low quality evidences).

Statement 15 In elderly patients operated for acute appendicitis, when post-operative antibiotic therapy is indicated, we suggest a period of 3-5 days although discontinuation of antimicrobial treatment should be based on clinical and laboratory criteria such as fever and leucocytosis (Conditional recommendation, low quality evidences).