The purpose of the trial is to compare the efficacy of Rifamycin SV-MMX® 400 mg b.i.d. vs. Rifamycin SV-MMX® 600 mg t.i.d. vs. placebo in patients with acute uncomplicated diverticulitis.

Inclusion Criteria:

1. Signed informed consent,
2. Patient is eligible for out-patient treatment,
3. Men or women between 18 and 80 years of age,
4. Diagnosis of left-sided uncomplicated diverticulitis confirmed by ultrasonography (US) and/or computed tomography (CT) according to modified Hinchey classification (stage 1a) or Hansen/Stock classification (stage I/IIa) or Ambrosetti classification (stage mild),
5. Presence of significant left lower quadrant pain during the last 24 hours before baseline,
6. CRP > ULN and/or leucocytosis (> ULN) at screening visit

Exclusion Criteria:

1. Existing complications of diverticulitis (diverticulitis with associated abscess, fistula, obstruction or perforation),
2. Right-sided diverticulitis,
3. Previous colonic surgery (except appendectomy, haemorrhoidectomy, and endoscopic removal of polyps),
4. Chronic inflammatory bowel disease (such as Crohn's disease, ulcerative colitis) or celiac disease,
5. Presence of symptomatic organic disease of the gastrointestinal tract (with the exception of non-bleeding hemorrhoids or hiatal hernia),
6. Hemorrhagic diathesis,
7. Active peptic ulcer disease,
8. Abnormal hepatic function or liver cirrhosis,
9. Abnormal renal function,
10. Colorectal cancer or a history of colorectal cancer,