The purpose of this study is to determine whether mesalamine is effective vs. placebo in the prevention of diverticulitis flares in a 24-months follow-up.

The primary end-point of the study is the incidence of diverticulitis flares. Will be made a clinical diagnosis of uncomplicated diverticulitis: fever, leukocytosis, abdominal pain and altered intestinal motility.

Inclusion Criteria:

• age ≥ 18 years
• both males and females patients
• positive history of acute diverticulitis flare during the last year. The patients will be recruited only after the complete clinical remission of diverticulitis flare.
• patients who have given their free and informed consent

Exclusion Criteria:

• complicated diverticulitis(fistulas, stenosis, abscesses and/or bleeding)
• ascertained hypersensitivity to the salicylates
• any severe pathology that can interfere with the treatment or the clinical or instrumental test of the trial
• clinically significant renal or hepatic impairment
• esophageal, gastric or duodenal ulcer within 30 days prior to randomisation
• patients with active malignancy of any type, or history of a malignancy (patients with a history of malignancies that have been surgically removed and who have no evidence of recurrence for at least five years before study enrollment are also acceptable)
• treatment with any investigational drug within the previous 30 days
• treatment with lactulose or with any compound that lowering the colonic pH can prevent the release of the active moiety from the tablets
• recent history or suspicion of alcohol abuse or drug addiction
• patients who become unable to conform to protocol
• patients with ascertained pregnancy
• previous participation in this study