Horizontal plane through the kidneys, showing subdivisions of the retroperitoneal space. The anterior and posterior pararenal spaces have been exaggerated to provide representation of their relation to other retroperitoneal structures.
Human kidneys viewed from behind with spine removed
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.
The difference from organs that is not retroperitoneum is that it is on the posterior side only and are suspended 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
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:
- Secondarily retroperitoneal, meaning the structures initially were suspended in mesentery and later migrated behind the peritoneum during development
- 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:
- Adrenal gland
- 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
- 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".
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
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- University of Michigan - Lab Manual - Kidneys & Retroperitoneum
- Raval, Bharat; Pollock, Raphael E.; Guadagnolo, Ashleigh; Patel, Shreyaskumar (1 January 2012). "Chapter 23 - Primary Retroperitoneal Tumors". Oncologic Imaging: A Multidisciplinary Approach. W.B. Saunders. pp. 403–421.