Final answer:
Retroperitoneal organs include the pancreas, the ascending colon, and the rectum which lie behind the peritoneum in the abdominal cavity.
Step-by-step explanation:
Retroperitoneal organs include most of the duodenum, the pancreas, the ascending colon, and descending colon of the large intestine, and the rectum. The pancreas is an elongated organ located behind the stomach in the retroperitoneum. The large intestine includes various parts such as the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum. The ascending and descending colon, as well as the rectum, are considered retroperitoneal organs because they lie behind the peritoneum, a membrane that lines the abdominal cavity.