MSFinals-6213
A 79-year-old man presents to the emergency department referred by his GP due to lower abdominal pain and distension for the past three days. He has been unable to pass stool or flatus. The patient had a laparotomy for a perforated duodenal ulcer 25 years ago. Upon examination, his abdomen is distended and non-tender, and he appears to be in obvious discomfort. The CT scan of his abdomen and pelvis reveals evidence of large bowel obstruction at the splenic flexure. What is the probable cause of his presentation?