The retroperitoneal space is an anatomical region situated directly behind the peritoneum. The peritoneum is a thin, serous membrane lining the abdominal cavity and covering many organs. Organs in the retroperitoneal space are either partially or not at all covered by the peritoneum, which gives them a fixed position unlike those suspended within the cavity.
Anatomical Location
The retroperitoneal space extends from the diaphragm, separating the chest from the abdomen, down to the pelvic brim. Its anterior boundary is the parietal peritoneum, which lines the abdominal wall. Posteriorly, it is bordered by posterior abdominal wall muscles, including the psoas major and quadratus lumborum, and their overlying fascia. Laterally, the space is less distinctly defined, where the parietal peritoneum reflects forward.
This region is often described as a potential space, meaning it is not an open cavity but rather a tightly packed area where structures are nestled together. On an axial cross-section, the retroperitoneum has a C-shape, with the convexity facing forward. While continuous, it is often subdivided into smaller compartments by fascia, such as the anterior pararenal, perirenal, and posterior pararenal spaces.
Organs in the Retroperitoneal Space
The retroperitoneal space contains a variety of organs and major blood vessels. These include structures that are primarily retroperitoneal, meaning they developed and remained in this position throughout fetal development. The kidneys, for instance, filter waste products from the blood and produce urine. The adrenal glands, situated atop the kidneys, produce hormones regulating metabolism and stress response. The ureters, tubes transporting urine from the kidneys to the bladder, also pass through this space.
Major blood vessels, such as the abdominal aorta and inferior vena cava (IVC), are also found here. The aorta, the body’s largest artery, distributes oxygenated blood to the lower body and organs. Conversely, the IVC collects deoxygenated blood from the lower limbs and abdomen, returning it to the heart. Several organs are considered secondarily retroperitoneal; they initially developed within the peritoneal cavity but later shifted to a retroperitoneal position during development. This group includes the majority of the pancreas, which produces digestive enzymes and hormones like insulin. Also found here are the second, third, and fourth parts of the duodenum, the first section of the small intestine involved in digestion, and the ascending and descending portions of the colon, which absorb water and form feces.
Clinical Relevance
Understanding the retroperitoneal space is important due to its complex anatomy and the vital organs it contains. Because of its deep and protected location, conditions affecting this area can be challenging to diagnose without advanced imaging. Medical professionals often rely on techniques like computed tomography (CT) scans or ultrasound to visualize structures within this region.
Issues arising in the retroperitoneal space can include fluid collections like hematomas (collections of blood) or abscesses (pockets of infection). Inflammation, such as pancreatitis, or abnormal growths like tumors, can also occur here. Symptoms can be vague, sometimes presenting as general abdominal discomfort or back pain, making diagnosis reliant on anatomical knowledge and imaging. The confined nature of the space means even small changes can exert pressure on surrounding organs and vessels, affecting their function and requiring careful medical management.