The retroperitoneum is the part of the abdominal cavity that lies between the posterior parietal peritoneum anteriorly and the posterior abdominal wall 4. It is C-shaped on axial cross-sections with a convexity projecting anteriorly in the midline.
Gross anatomy
The retroperitoneum is variably defined, mostly by the lack of consensus definition for the posterior abdominal and whether the psoas muscles and quadratus lumborum are boundaries or contents 4. It can have up to five compartments depending on definition:
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lateral compartments divided into three spaces by renal fascia 4
great vessel compartment: from T12 to L4/5 between perirenal space 2,3
posterior compartment: containing psoas muscles, which join iliacus behind transversalis fascia, quadratus lumborum 4
Perirenal space
inverted cone shape with its base resting on diaphragm and its point directed towards the pelvis
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boundaries
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anterior and posterior renal fascia are continuous with each other (fascia of Gerota and Zuckerkandl, respectively)
the anterior renal fascia blends anteriorly with connective tissue around the aorta and the inferior vena cava
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the posterior renal fascia (thicker, two lamina) blends with the quadratus lumborum fascia
superficial lamina is made up of lateroconal fascia which extends anteriorly and attaches to peritoneum
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contents: adrenal gland, kidney, renal pelvis, proximal ureter, renal hilar vessels, lymph nodes, fat
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relations
upper right perirenal space communicates with the retrohepatic space at the bare area of the liver
posterior pararenal space related posteriorly
anterior pararenal space related anteriorly
the Kneeland space is a theoretical communication between both perirenal spaces, anterior to the aorta and inferior vena cava
Anterior pararenal space
boundaries: posterior parietal peritoneum anteriorly, anterior renal fascia posteriorly, and lateroconal fascia (continuation of posterior renal fascia) laterally
contents: duodenum (D2-D4), ascending and descending colon, pancreas, lymph nodes, fat
relations: potentially continuous across midline, peritoneal space anteriorly, perirenal space posteriorly
Posterior pararenal space
boundaries: posterior renal fascia anteriorly, transversalis fascia posteriorly
contents: fat
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relations
communicates with the properitoneal space in the anterior abdomen between the peritoneum and the transversalis fascia
communicates potentially with the contralateral side
communicates with the flank laterally (external to lateroconal fascia and deep to transversalis fascia); visualized as flank strip radiologically
opens inferiorly towards pelvis, following length of ureter
Great vessel compartment
not well-defined by fascial planes
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boundaries
laterally: perirenal space and ureter
posteriorly: vertebral body, psoas major muscle
superiorly: continuous with the posterior mediastinum
contents: aorta, inferior vena cava, fat, lymph nodes