Retroperitoneal space

Retroperitoneal space
The retroperitoneal space (retroperitoneum) is the anatomical space (sometimes a potential space) behind (retro) 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.
This is different from organs that are not retroperitoneal, which have peritoneum on their posterior side and are suspended by mesentery in the abdominal cavity.
The retroperitoneum can be further subdivided into the following:
Perirenal (or perinephric) space
Anterior pararenal (or paranephric) space
Posterior pararenal (or paranephric) 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:
urinary
adrenal glands
kidneys
ureter
circulatory
aorta
inferior vena cava
digestive
anal canal
Secondarily retroperitoneal, meaning the structures initially were suspended in mesentery and later migrated behind the peritoneum during development
the duodenum, except for the proximal first segment, which is intraperitoneal
ascending and descending portions of the colon (but not the transverse colon, sigmoid and the cecum)
pancreas, except for the tail, which is intraperitoneal
Subdivisions
Perirenal space
It is also called the perinephric space. Bounded by the anterior and posterior leaves of the renal fascia. It contains the following structures:
Adrenal gland
Kidney
Renal vessels
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:
Pancreas
Ascending and descending colon
Duodenum
Posterior pararenal space
Bounded by the posterior leaf of the renal fascia and the muscles of the posterior abdominal wall. It contains only fat ("pararenal 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.
Retroperitoneal fibrosis
Retroperitoneal lymph node dissection
It is also possible to have a neoplasm in this area, more commonly a metastasis; or very rarely a primary neoplasm. The most common type is a sarcoma followed by lymphoma, extragonadal germ cell tumor, and gastrointestinal stromal tumor/GIST. Examples of tumors include
Primary peritoneal carcinoma
Pseudomyxoma peritonei
Examples of sarcomas include:
Soft-tissue sarcoma
liposarcoma
leiomyosarcoma
Undifferentiated pleomorphic sarcoma, a clinically distinct sarcoma of the area
See also
Intraperitoneal
Retropubic space
Rectovesical pouch
Vesicouterine pouch
Rectouterine pouch (Pouch of Douglas)
References
Abdomen