Retroperitoneal Space

Retroperitoneal space is the anatomical space in the abdominal cavity behind the parietal peritoneum. It extends from the 12th thoracic vertebra and 12th rib above to the sacrum and iliac crest below.

The floor of the space, that is the posterior wall of the abdomen in this region, is formed by;

  • Psoas muscle
  • Quadratus lumborum muscle
  • Origin of transverses abdominis muscle

Each of these structures is covered on the anterior side by a well-defined layer of fascia, in front of which is a variable amount of fatty connective tissue. This fat forms a bed for the suprarenal glands, kidneys, ascending and descending parts of colon and duodenum.

Retroperitoneal structures:

These are structures which contain peritoneum only on their anterior surfaces. There are two types of retroperitoneal organs: Primary retroperitoneal and Secondary retroperitoneal.

Primary retroperitoneal:

These are structures which are retroperitoneal from the start of their development. These include:

Urinary structures

  • Suprarenal glands
  • Kidneys
  • Ureters
  • Bladder

Circulatory structures

  • Aorta
  • Inferior vena cava

Digestive structures

  • Part of esophagus
  • Part of rectum

Secondary retroperitoneal:

These are structures which were once suspended within the abdominal cavity by mesentery but migrated posteriorly behind the peritoneum during the course of development. These include

  • Pancreas (except the tail)
  • Duodenum (except the 1st part)
  • Ascending colon
  • Descending colon

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 parts)
  • K = Kidneys
  • E = Esophagus
  • R = Rectum