A 62-year-old man presented with left lower quadrant pain. Computed tomography (CT) showed sigmoid diverticulitis with a microperforation and a 1.5-cm intramural abscess. He had a similar episode 1 year ago. His last colonoscopy was 10 years ago, and it was normal except for sigmoid diverticulosis. After conservative management, the inflammation resolves and the patient presents to your clinic for follow-up. The recommended next step in management is