Acute diverticulitis is a common disease in the western world. Perforation of the acute diverticulitis with peritonitis is a feared complication and standard treatment (primary sigmoid resection such as Hartmann`s procedure) still has unsatisfactory results. Both mortality and morbidity are quite high. Several uncontrolled trials have reported a lower mortality and morbidity when acute perforated diverticulitis is treated with laparoscopic lavage instead of radical surgery. The investigators wish to conduct a randomized multicenter trial in Scandinavia in order to compare the rates of severe postoperative complications in acute perforated diverticulitis if treated by traditional primary sigmoid resection or by laparoscopic lavage. The investigators are planning to include all patients admitted to the participating hospitals with clinical and radiological findings of acute perforated diverticulitis.