The purpose of this study is to compare the efficacy (by assessing the clinical success of treatment) of intravenous antibiotic therapy with ertapenem in patients with acute attacks of sigmoid diverticulitis for 4 vs. 7 days.

Inclusion Criteria:

• At least three of the following signs or symptoms of an acute attack of sigmoid diverticulitis must be present: *Fever (body temperature > 38°C, sublingual), *Abdominal tenderness, *Leukocytosis (leukocytes > 10,000/µl) and left shift of the differential blood count (>1% band forms), *Elevated CRP (> 20 mg/l)
• Evidence of sigmoid diverticulitis by contrast enema
• CT evidence of wall thickening in the sigmoid intestine
• Decision in favor of conservative therapy on the basis of the case history and diagnosis

Exclusion Criteria:

• Contraindication for the use of the study medication or other beta-lactam antibiotics, e.g. patients with advanced renal impairment or patients requiring hemodialysis
• Antibiotic therapy in the two weeks prior to the start of the study
• Patients with an advanced incurable disease
• Patients with a hematologic/oncologic disease (leukemia, lymphoma)
• Patients on immunosuppressants
• Complications of sigmoid diverticulitis leading to an immediate indication for surgery
• Patients who have hypersensitivity to beta-lactam antibiotics
• Female patients who are pregnant or nursing or who could become pregnant during the study
• Participation in another clinical study or use of another study drug within the four weeks prior to enrollment in the study or use of another drug during the study
• Each patient can be enrolled only once in the study