Anatomy
Retroperitoneum is the part of the abdominal cavity that lies between the posterior parietal peritoneum and anterior to the transversalis fascia.
Abdominal retroperitoneum
Tricompartmental retroperitoneum Fig. 1a
Anterior pararenal space (APS)
• Most anterior space of retroperitoneum
• Bounded anteriorly by posterior peritoneal fold and posteriorly by anterior renal fascia
• Contents : pancreas, duodenum, ascending & descending colon
Perirenal space (PS)
• Bounded anteriorly by Gerota fascia and posteriorly by Zuckerkandl fascia which join laterally to form lateroconal fascia
• Contents: kidneys, proximal collecting system, renal vasculature and adrenal glands
Posterior pararenal space (PPS)
• Most posterior space of retroperitoneum
• Bounded anteriorly by posterior renal fascia & lateroconal fascia and posteriorly by transversalis fascia
• Contents: fat
• It has anatomical continuity with pro-peritoneal space
Multilaminated retroperitoneum Fig. 1b , Fig. 2
• Retromesenteric plane (RMP) is a potentially expansile plane located between anterior pararenal space and perirenal space & communicates across midline
• Retrorenal plane (RRP) is located between the perirenal space and posterior pararenal space. It contains aorta & IVC
• Lateral conal interfascial plane lies between the layers of the lateroconal fascia and communicates with the RMP & RRP at the fascial trifurcation
• Combined interfascial plane (CIP): RRP combines with the RMP inferiorly to form the CIP, which extends into the pelvic retroperitoneum
Pelvic retroperitoneum Fig. 3
• It is the downward extension of abdominal retroperitoneum with which it connects by means of CIP.
• It is divided into two compartments by rectoprostatic fascia in males & rectovaginal fascia in females
- Anterior compartment: prevesical space, paravesical space
- Posterior compartment : pararectal space, presacral space
Presence of several weak areas (neurovascular and muscle structures) open pathways of communication between abdominal retroperitoneum with extraperitoneal regions such as scrotum and thigh.
Imaging
• CT plays an important role in emergency situations because of its short acquisition time
• 3D MPR enables accurate evaluation of complex anatomy of retroperitoneal spaces
• Once pneumoretroperitoneum is confirmed, CT helps to locate the source of air which is pertinent for its management