The medical management of diverticulitis has evolved considerably with the advent of outpatient antibiotic management and recommendations to treat uncomplicated diverticulitis with antibiotic therapy alone. Many patients who present after a failure of outpatient medical management or with advanced stages of complicated diverticulitis often require inpatient therapy involving intravenous antibiotic therapy with a source control procedure. Complicated cases of diverticulitis which previously mandated operative therapy, including resection with or without diversion, are now more commonly being managed nonoperatively. This chapter will explore the evolution of the nonoperative treatment of diverticular abscess, the evidence behind new interventional nonoperative procedures, and the future regarding the management of complicated diverticulitis.