Retroperitoneum anatomy by Dr. A.Sabith Meeran , MD Radiodiagnosis

retroperitoneal anatomy and related pathologies

1. Retroperitoneum anatomy and related pathologies Presentor – Dr. A.Sabith Meeran

2. 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.

3. Boundaries of retroperitoneum Anteriorly : by posterior parietal peritoneum Posteriorly : by transversalis fascia Extends craniocaudally from diaphragm to pelvic brim

4. ( The retroperitoneum can be further subdivided into three spaces by perirenal fascia (fascia of gerota and zukerkandl ) . Perirenal (or perinephric) space Anterior pararenal (or paranephric) space Posterior pararenal (or paranephric) space

5. Primary 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

6. Secondary retroperitoneal organs 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

7. Anterior pararenal space Boundaries: Anteriorly : by posterior parietal peritoneum Posteriorly: by anterior renal fascia It contains the following structures: Pancreas Ascending and descending  colon Duodenum

8. Posterior pararenal space Boundaries: Anteriorly : by posterior renal fascia and lateral conal fascia Posteriorly : by transversalis fascia Open laterally to frank and inferiorly to pelvis Contents : fat and no visceral organ.

9. Pararenal fat Pararenal fat is a fatty layer situated posterior to the renal compartment, and extending inferiorly into the  iliac fossa  It is situated posterior to the posterior aspect of  renal fascia , and anterior to the aponeuroses of the retrorenal muscles. It is plentiful in the  dihedral angle  of the  iliopsoas muscle  and the  quadratus lumborum muscle , filling the lumbar fossa posterior and inferior to the kidney.

10. Peri renal space Boundaries : Superior:open to bare area of liver and contiguous withwith mediastinum Medial : anterior and posterior renal fascia fuse. Lateral:lateral conal fascia Inferior : anterior renal fascia and posterior renal fascia convergeblend about 8 cm below the kidney

11. Kunin septa Perinephric bridging septa  or  septa of Kunin  (singular: septum) are composed of numerous fibrous lamellae which traverse the perinephric fat  1,2  where they suspend the  kidneys  within the  perirenal space . The septa may act as a barrier or conduit for the spread of pus, blood, urine, and neoplasms in the perinephric space. The septa were first described by  Milton   Kunin , an American uroradiologist

12. Three types of bridging septa have been described: renorenal : septa running parallel to the renal capsule and attaching back onto the kidney renofascial : septa connecting the capsule to the adjacent anterior or posterior renal fascia interconnecting fascia: connecting the anterior and posterior layers of the perinephric fascia

13. Iliopsoas compartment The  iliopsoas compartment  is an extra-retroperitoneal space that runs along the posterior aspect of the abdomen and pelvis and extends into the  thigh . Boundaries: The iliopsoas compartment is bound by the iliopsoas fascia, which is continuous with: anteriorly:  transversalis fascia superiorly:  endothoracic fascia inferiorly:  fascia lata of the thigh

14. Contents psoas major muscle psoas minor muscle iliacus muscle lumbar plexus

15. Interfascial planes These planes are represented by Retromesentric plane Retrorenal plane Lateroconial interfascial plane Combined interfascial plane These are potential routes of interfascial communications Retroperitoneal haemorrhage and fluid collections are spread by these planes.

16. Interfascial extentions

17. Identification of origin of organs Some radiological signs that are helpful in determining the origin include Beak sign Phantom organ sign Embedded organ sign Feeding artery sign

18. liposarcoma Most common retroperitoneal sarcoma Divided into 4 types : well differentiated ,myxoid , dedifferentiated ,pleomorphic

19. Retroperitoneal fibrosis Retroperitoneal fibrosis (RPF) , is a condition that has previously been described as  chronic periaortitis .  It is an uncommon fibrotic reaction in the  retroperitoneum that typically presents with  ureteric obstruction The disease is part of a spectrum of entities that have a common pathogenic process consisting of an inflammatory response to advanced atherosclerosis of the abdominal aorta, combined with autoimmunologic factors: idiopathic retroperitoneal fibrosis perianeurysmal retroperitoneal fibrosis isolated periaortitis : corresponds to a non-aneurysmal form of chronic periaortitis inflammatory abdominal aortic aneurysm

20. Maiden waist sign in retroperitoneal fibrosis

21. Retroperitoneal haemorrhage