Intraperitoneal organs are peritoneal organs that have an associated mesentery, such as the stomach, small intestine (jejunum and ileum), transverse and sigmoid colon, liver, and gallbladder.

Retroperitoneal organs do not have a mesentery and are associated with the posterior body wall. Retroperitoneal organs are subdivided into two categories: primarily retroperitoneal and secondarily retroperitoneal. Primarily retroperitoneal organs were present posterior to the peritoneal cavity in the embryo, such as the aorta, inferior vena cava, ureters, kidneys, and suprarenal glands. Secondarily retroperitoneal organs become fused to the posterior abdominal wall during development.