Surgical anatomy of the retroperitoneal spaces--part I: embryogenesis and anatomy.

Embryologically, the retroperitoneal (extraperitoneal) connective tissue includes three strata, which respectively form the internal fascia lining of the body wall, the renal fascia, and the covering of the gastrointestinal viscera. All organs, vessels, and nerves, that lie on the posterior abdominal wall, along with their tissues and surrounding connective and fascial planes, are collectively referred to as the retroperitoneum. The retroperitoneal space is the area of the posterior abdominal wall that is located between the parietal peritoneum and the fascia. Within the greater retroperitoneal space, there are also several small spaces, or subcompartments. Loose connective tissue and fat surround the anatomic entities, and, to a variable degree, occupy the subcompartments. The multilaminar thoracolumbar (lumbodorsal) fascia begins at the occipital area and terminates at the sacrum.