Table 1 Summary of recommendations

Diagnosis

Statement 1.1 In the elderly population, we suggest against basing the diagnosis of acute left colonic diverticulitis on only patient clinical signs, symptoms and laboratory tests. [Conditional recommendation, very low-quality evidence]

Statement 1.2 We suggest that elderly patients presenting with abdominal guarding or pain in the lower left abdomen on physical examination undergo appropriate imaging for suspected diverticulitis, regardless of the value of leukocytes and of C-reactive protein (CRP). [Conditional recommendation, very low-quality evidence]

Statement 2.1 We suggest the use of CT-scan with IV-contrast in all elderly patients with suspected diverticulitis to confirm the diagnosis and to distinguish complicated from non-complicated diverticulitis. [Conditional recommendation, very low-quality evidence]

Statement 2.2 In elderly patients with suspected diverticulitis who cannot undergo CT-scan with IV-contrast (i.e. severe acute or chronic kidney disease or contrast allergy), we suggest the use of US, MRI or CT-scan without IV-contrast as alternative diagnostic approaches, according to resources availability. [Conditional recommendation, very low-quality evidence]

Management

Statement 3.1 We suggest that antibiotic therapy should be avoided in immunocompetent elderly patients with uncomplicated left colonic diverticulitis (WSES stage 0) without sepsis-related organ failures [Conditional recommendation, very low-quality of evidence]

Statement 4.1 We suggest antibiotic therapy administration for elderly patients with localized complicated left colonic diverticulitis with pericolic air bubbles or little pericolic fluid without abscess (WSES stage 1a). [Conditional recommendation, moderate quality of evidence]

Statement 5.1 In elderly stable patients with an abscess from acute left colonic diverticulitis (WSES stage 1b-2a) and without peritonitis, we suggest the administration of a broad-spectrum antibiotic therapy. [Conditional recommendation, very low quality of evidences]

Statement 5.2 We suggest adding percutaneous drainage to antibiotic therapy in elderly patients with acute left colonic diverticulitis and an abscess larger than 4 cm (WSES stage 2a), when skills and facilities are available. Cultures from percutaneous drainage should be carried out to guide the antibiotic therapy. [Conditional recommendation, very low quality of evidences]

Statement 6.1: In elderly patients with acute left colonic diverticulitis and CT findings of distant intraperitoneal free air and no free fluid (WSES stage 2b), we suggest against non-operative management as a viable option. [Conditional recommendation, very low quality of evidences]

Statement 7.1 In elderly patients with acute left colonic diverticulitis and diffuse peritonitis (WSES stage 3–4), we recommend against non-operative management as a viable option. [Strong recommendation, very low quality of evidences]

Statement 7.2 In elderly patients with acute left colonic diverticulitis and diffuse peritonitis (WSES stage 3–4), we recommend prompt and effective source control surgery. [Strong recommendation, very low quality of evidences]

Statement 8.1 We suggest against elective sigmoid resection after a conservatively treated episode of acute left colonic diverticulitis in asymptomatic elderly patients without stenosis, fistulae or recurrent diverticular bleeding. [Conditional recommendation, very low-quality evidence]

Statement 8.2 We suggest to consider elective sigmoid resection after a conservatively treated episode of acute left colonic diverticulitis in high-risk elderly patients, such as immunocompromised patients (if fit for surgery). [Conditional recommendation, very-low quality evidence]

Statement 8.3 We suggest elective sigmoid resection in elderly patients (if fit for surgery) with left colonic diverticular disease complicated with stenosis, fistulae or recurrent diverticular bleeding. [Conditional recommendation, very low-quality evidence]

Statement 8.4 We suggest elective sigmoid resection in elderly patients (if fit for surgery) with very symptomatic left colonic diverticular disease which compromise the quality of life. [Conditional recommendation, very low-quality evidence]

Statement 9.1 We suggest planning early colonic evaluation in elderly patients after an episode of acute left colonic diverticulitis. [Conditional recommendation, very low-quality evidence]

Surgical technique

Statement 10.1 In elderly patients with acute left colonic diverticulitis and acute peritonitis, we suggest against laparoscopic lavage as the preferred surgical approach due to the higher risk of failure to control the source of sepsis. [Conditional recommendation, moderate quality evidences]

Statement 11.1 We suggest that in elderly patients with perforated diverticulitis with generalized peritonitis Hartmann operation and resection with primary anastomosis are both reasonable options. [Conditional recommendation, low-quality of evidence]

Statement 11.2 We suggest that in elderly patients with perforated diverticulitis with generalized peritonitis and physiological derangement, Damage Control Surgery (emergency laparotomy, source control and application of open abdomen and abdominal vacuum-assisted closure) may be a viable option. [Conditional recommendation, very low quality of evidence]

Statement 12.1 We suggest that in stable elderly patients with perforated diverticulitis with diffuse peritonitis emergency laparoscopic sigmoidectomy can be performed by experienced laparoscopic surgeons [Conditional recommendation, very low quality of evidence]

Antibiotic therapy

Statement 13.1 In elderly patients with localized complicated diverticulitis the empirically designed anti-microbial regimen depends on the underlying clinical condition of the patient, the pathogens presumed to be involved, and the risk factors indicative of major resistance patterns. [Conditional recommendation, very low quality of evidence]

Statement 14.1 In elderly patients with perforated diverticulitis with diffuse peritonitis the empirically designed anti-microbial regimen depends on the underlying clinical condition of the patient, the pathogens presumed to be involved, and the risk factors indicative of major resistance patterns. [Conditional recommendation, very low quality per indirectness]

Statement 15.1 In elderly patients with complicated diverticulitis a short course of antibiotic therapy (3–5 days) after adequate source control is a reasonable option. [Conditional recommendation, moderate quality of evidence]

Statement 15.2 In elderly patients with complicated diverticulitis who have ongoing signs of peritonitis or systemic illness (ongoing infection) beyond 5 to 7 days of antibiotic treatment, further diagnostic investigation is indicated. [Conditional recommendation, low quality of evidence]