Retroperitoneum

Retroperitoneum
Transverse section, showing the relations of the capsule of the kidney. (Peritoneum is labeled at center right.)
Human kidneys viewed from behind with spine removed
Latin	spatium retroperitoneale
MeSH	Retroperitoneal+Space

The retroperitoneum (or extraperitoneum) is the anatomical space in the abdominal cavity behind (retro) the peritoneum. It has no specific delineating anatomical structures. Organs are retroperitoneal if they only have peritoneum on their anterior side.

The retroperitoneam can be further subdivided into the^[1]:

• 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:
  • urinary
    • adrenal glands
    • kidneys
    • ureter
    • bladder
  • circulatory
    • aorta
    • inferior vena cava
  • digestive
    • esophagus (part)
    • rectum (part, lower third is extraperitoneal)

• Secondarily retroperitoneal:
  • the head, neck, and body of the pancreas (but not the tail, which is located in the splenorenal ligament)^[2]
  • the duodenum, except for the proximal first segment, which is peritoneal^[3]
  • ascending and descending portions of the colon (but not the transverse or sigmoid)

A useful mnemonic to aid recollection of the abdominal retroperitoneal viscera is SAD PUCKER:

• S = Suprarenal glands (aka the adrenal glands)
• A = Aorta/IVC
• D = Duodenum (second and third segments [some also include the fourth segment] )
• P = Pancreas (tail is intraperitoneal)
• U = Ureters
• C = Colon (only the ascending and descending branches)
• K = Kidneys
• E = Esophagus
• R = Rectum

Perirenal Space

Bounded by the anterior and posterior leafs of the renal fascia. It contains the:

• Adrenal Gland
• Kidney
• Renal Vessels

Anterior pararenal space

Bounded by the posterior layer of peritoneum and the anterior leaf of the renal fascia. It contains the:

• Pancreas
• Ascending and Descending Colon
• Retroperitoneal duodenum
• Aorta and IVC

Posterior pararenal space

Bounded by the posterior leaf of the renal fascia and the muscles of the posterior abdominal wall. It contains only fat.

Role in disease

• Retroperitoneal fibrosis
• Retroperitoneal Lymph Node Dissection
• Retroperitoneal bleeding, such as from a ruptured aortic aneurysm shows as Grey Turner's sign (flank bruising).

References