What is the Retroperitoneum?
The retroperitoneum is the anatomical space located behind the parietal peritoneum and in front of the transversalis fascia, extending from the diaphragm superiorly to the pelvic brim inferiorly. 1, 2
Anatomical Boundaries and Structure
The retroperitoneum is a compartmentalized space with clearly defined borders:
- Anterior boundary: Posterior parietal peritoneum 1, 2
- Posterior boundary: Transversalis fascia 1, 2
- Superior extent: Diaphragm 2
- Inferior extent: Pelvic brim 2
Subdivisions and Compartments
The retroperitoneum is divided into three distinct compartments, each containing specific organs and structures 1, 3:
Perirenal Space
- Shape: Inverted cone configuration 1
- Contents: Kidneys, adrenal glands, and their associated vasculature 1
- Boundaries: Delineated by anterior and posterior renal fasciae 1
- Communication: Connects to the retrohepatic space at the bare area of the liver through the Kneeland channel at the upper right pole 1
- Extension: Surrounds the ureter and allows communication toward the pelvis 1
Anterior Pararenal Space
- Contents: Duodenum, pancreas, ascending colon, and descending colon 1
- Communication: Free communication within this space and toward the mesenteries along the vessels 1
Posterior Pararenal Space
- Contents: Primarily fat 1
- Communication: Connects with the preperitoneal space at the anterior abdominal surface between the peritoneum and transversalis fascia 1
- Lateral extension: Allows communication with the contralateral posterior pararenal space 1
- Inferior extension: Follows the length of the ureter to the pelvis 1
Fascial Architecture
The retroperitoneum contains multilaminated fascial structures rather than distinct unilaminated layers, creating potential spaces that are clinically significant 3:
These potential spaces allow for interfascial spread of pathologic processes between the peritoneal cavity and pelvis 1.
Clinical Significance
Understanding retroperitoneal anatomy is critical because this space contains vital organs and serves as a pathway for disease spread 4:
- Pathologic fluid collections: Inflammatory effusions, hematomas, and abscesses can track through fascial planes 4
- Neoplastic processes: Retroperitoneal sarcomas (liposarcomas, leiomyosarcomas, solitary fibrous tumors) arise in this space and have specific surgical considerations based on their location and relationship to vital structures 5
- Vascular complications: Retroperitoneal hematomas can result from anticoagulation, trauma, vascular rupture, or iatrogenic injury 6, 7
Common Pitfalls
The retroperitoneum's complex fascial anatomy and potential spaces mean that pathologic processes can spread extensively before becoming clinically apparent, as symptoms are often nonspecific (diffuse abdominal pain, back pain, flank pain, or abdominal distension) 6, 7.