The purpose of this case is to highlight a rare case of sigmoid colon-to-rectum fistula. A 66-year-old man with a history of pelvic radiation and diverticulosis presented to the emergency department with a 3-week history of abdominal pain and watery diarrhea. Computed tomography (CT) imaging was significant for a sigmoid-to-rectum fistula with sigmoid stricture. The patient underwent a laparoscopic colectomy with end colostomy. Pathology revealed perforated diverticulitis. To date, there have been no cases reported in literature describing sigmoid-to-rectum fistula. In conclusion, it is important to consider the development of complex diverticular disease in patients with history of pelvic radiation
