A 50-year-old man presents with complaints of recurrent urinary tract infections and pneumaturia. Computed tomography demonstrates a thickened sigmoid colon immediately adjacent to the dome of the urinary bladder. The bladder wall is thickened and an air-fluid level is present within the bladder. His first screening colonoscopy was performed 3 months ago and demonstrated sigmoid diverticulosis with no other suspicious findings. What is the best next step in management?