The retroperitoneal space is the anatomical space in the abdominal cavitybehind the peritoneum. It has no specific delineating anatomical structures. Organs are retroperitoneal if they have peritoneum on their anterior side only. Structures that are not suspended by mesentery in the abdominal cavity and that lie between the parietal peritoneum and abdominal wall are classified as retroperitoneal. The retroperitoneum can be further subdivided into the following:
Perirenal space
Anterior pararenal space
Posterior pararenal space
Retroperitoneal structures
Structures that lie behind the peritoneum are termed "retroperitoneal". Organs that were once suspended within the abdominal cavity by mesentery but migrated posterior to the peritoneum during the course of embryogenesis to become retroperitoneal are considered to be secondarily retroperitoneal organs.
Primarily retroperitoneal, meaning the structures were retroperitoneal during the entirety of development:
* pancreas, except for the tail, which is intraperitoneal
Subdivisions
;Perirenal space It is also called the perinephric space. Bounded by the anterior and posterior leafs of the renal fascia. It contains the following structures:
Perirenal fat, which is also called the "adipose capsule of the kidney" and may be regarded as being part of the renal capsule
;Anterior pararenal space Bounded by the posterior layer of peritoneum and the anterior leaf of the renal fascia. It contains the following structures:
;Posterior pararenal space Bounded by the posterior leaf of the renal fascia and the muscles of the posterior abdominal wall. It contains only fat, and is also called the "paranephric body", or "pararenal fat body".
Clinical significance
Bleeding from a blood vessel or structure in the retroperitoneal such as the aorta or inferior vena cava into the retroperitoneal space can lead to a retroperitoneal hemorrhage.
