The goal of the COSMID (Comparison of Surgery and Medicine on the Impact of Diverticulitis) trial is to determine if elective colectomy is more effective than best medical management for patients with quality of life-limiting diverticular disease. The COSMID trial focuses on both patient-reported outcomes and clinical outcomes that matter to patients. The results are expected to establish an evidence-based approach to the care of millions of patients per year in the United States and help people impacted by this common condition make more informed treatment decisions.