From the Research
The retroperitoneal fat anterior to the psoas muscle and caudal to the lower pole of the left kidney typically contains the left ureter, lymphatic vessels, lymph nodes, and branches of the genitofemoral nerve. This anatomical region is part of the retroperitoneal space, which is an important area for radiologists and surgeons to evaluate when examining abdominal imaging. The left ureter is the most clinically significant structure in this location, as it travels from the renal pelvis downward along the anterior border of the psoas muscle toward the bladder. Lymph nodes in this area are part of the para-aortic chain and can be sites of metastatic disease from pelvic or retroperitoneal malignancies, as noted in a study on psoas lymph node metastasis in patients with carcinoma of the uterine cervix 1. Small blood vessels including branches of the lumbar arteries and veins may also traverse this fat plane, as described in a study on the surgical anatomy of the retroperitoneal spaces 2. Pathological processes that can affect this region include retroperitoneal fibrosis, lymphadenopathy, ureteral stones, and metastatic disease. When evaluating imaging of this area, careful attention should be paid to the course of the ureter and any abnormal soft tissue densities that might represent pathology, with consideration of the cleft of psoas major (CPM) and its contents, including neurovascular structures, as identified in a recent study 3. Key structures to consider in this region include:
- Left ureter
- Lymphatic vessels and lymph nodes
- Branches of the genitofemoral nerve
- Small blood vessels, including branches of the lumbar arteries and veins
- Cleft of psoas major (CPM) and its contents, including neurovascular structures.