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The retroperitoneal space (retroperitoneum) is the anatomical space (sometimes a potential space) in the abdominal cavity 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.〔Gray's Anatomy for Students, 2nd Ed. 2010. Pg. 251〕 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: * * urinary * * * adrenal glands * * * kidneys * * * ureter * * circulatory * * * aorta * * * inferior vena cava * * digestive * * * esophagus (thoracic part, part inside abdominal cavity is intraperitoneal) * * * rectum (part, lower third is extraperitoneal) * Secondarily retroperitoneal, meaning the structures initially were suspended in mesentery and later migrated behind the peritoneum during development: * * the head, neck, and body of the pancreas (but not the tail, which is located in the splenorenal ligament) * * the duodenum, except for the proximal first segment, which is intraperitoneal * * ascending and descending portions of the colon (but not the transverse colon, sigmoid or the cecum) 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 (also include the fourth segment ) ) * P = Pancreas (only head, neck, and body are retroperitoneal. The tail is intraperitoneal) * U = Ureters * C = Colon (only the ascending and descending colons, as transverse and sigmoid retain mesocolon) * K = Kidneys * E = Esophagus (not including the part inside the abdominal cavity) * R = Rectum Another mnemonic going along with SAD PUCKER is 112 212111, this correlating to which ones are Primarily (1) or Secondarily (2) Retroperitoneal. Alternatively, PADD (Pancreas, Ascending colon, Descending colon, Duodenum) can be used to remember which structures are secondarily retroperitoneal. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Retroperitoneal space」の詳細全文を読む スポンサード リンク
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