Patients presenting in hospital with symptoms of acute diverticulitis. Acute inflammation of the left-sided colon is confirmed with CT scan or ultrasound in experienced centers and diagnosis is defined according to the Classification of Diverticular Disease (CDD). CDD Type 2a, 2b and 3b will be included and then randomized in two groups. Group A will get an early left hemicolectomy 7 to 10 days after admission and initial antibiotic therapy and/or drainage of the abscess. Group B is designated for an elective resection 6 to 8 weeks after dismissal at the earliest and initial conservative treatment and/or after drainage of the abscess. Six weeks after the operation patients of Group A will be asked for their present quality of life with a standardized scoring system (Gastrointestinal Quality of Life Index = GIQLI; Short-form 36 Score = SF-36 Score; Low anterior resection syndrome = LARS Score). Group B (elective resection) will be asked at their readmission prior to elective surgery is done. This survey package will be repeated again 6 to 8 weeks later in both groups. Primary endpoints will be the two GIQLI at the said examination times. Secondary endpoints will be SF-36 score, LARS-score, GIQLI-Domains, anastomosis insufficiency and other complications, mortality and length of hospital stay. Comparisons between the groups are made at the said examination times but also 6-8 weeks after the operation.