The kidneys are bean-shaped organs that are found in the abdominal cavity. The peritoneum lies to the front of the abdominal cavity.

Kidneys are retroperitoneal. There are in the abdominal cavity, but not in the peritoneal cavity.

Abdominal cavity

Kidneys are retroperitoneal and so lie between the peritoneum and the abdominal wall, in the retroperitoneal space (a part of the abdominal cavity).

The kidneys lie behind the abdominal cavity in the retroperitoneal space. This anatomical space actually contains no structures.