Having to do with the area outside or behind the peritoneum (the tissue that lines the abdominal wall and covers most of the organs in the abdomen).

Why is it called retroperitoneal?

Through the course of embryogenesis, they became retroperitoneal as their mesentery fused with the posterior abdominal wall. Thus, in adults, only their anterior surface is covered with peritoneum. Examples of secondarily retroperitoneal organs include the ascending and descending colon.

What are retroperitoneal organs give examples?

The retroperitoneal space contains the kidneys, adrenal glands, pancreas, nerve roots, lymph nodes, abdominal aorta, and inferior vena cava.