Obturator Fossa Contents
The obturator fossa contains lymph nodes (obturator lymph nodes), the obturator nerve, obturator vessels (artery and vein), and surrounding fibro-fatty tissue. 1
Anatomic Boundaries and Structures
The obturator fossa is a critical anatomic space in pelvic surgery with well-defined boundaries:
- Medial boundary: The obturator nerve defines the medial limit of dissection 1
- Lateral boundary: The pelvic sidewall and external iliac vessels 1
- Superior extent: Extends cranially along the obturator nerve 1
- Inferior extent: Extends caudally to the obturator nerve 1
Lymph Node Contents
The obturator fossa is a key nodal basin for multiple pelvic malignancies:
- Lymph node distribution: Contains 12-20 lymph nodes as part of pelvic lymph node dissection 1
- Nodal tissue location: All fibro-fatty tissue within the obturator fossa should be removed during complete dissection to skeletonize the obturator nerve 1
- Drainage patterns: The obturator nodes receive lymphatic drainage from bladder, prostate, endometrium, ovary, cervix, and rectum 1
Neurovascular Structures
The obturator nerve and vessels are the critical neurovascular contents:
- Obturator nerve: Runs through the fossa and supplies the adductor muscles of the thigh; injury causes weakness in thigh adduction and difficulty ambulating 2, 3
- Obturator vessels: The obturator artery and vein accompany the nerve through the fossa 4
- Fascial relationships: A distinct fascial plane exists deep to the adductor muscles, overlying the anterior division of the obturator nerve 4
Clinical Significance in Lymphadenectomy
Extended pelvic lymph node dissection includes systematic removal of obturator fossa contents:
- Standard dissection template: Includes nodes overlying the external iliac vessels, nodes within the obturator fossa (cranial and caudal to the obturator nerve), and nodes medial and lateral to the internal iliac artery 1
- Surgical technique: Complete skeletonization of the obturator nerve is performed by removing all fibro-fatty tissue within the fossa 1
- Nerve preservation: The obturator nerve itself must be identified and preserved during dissection to avoid postoperative neuropathy 5, 3
Common Pitfalls
- Nerve injury: Obturator nerve transection or compression can occur during lymphadenectomy, resulting in adductor weakness and medial thigh pain 6, 5, 2
- Incomplete dissection: Failure to completely dissect the obturator fossa increases false-negative rates in cancer staging 1
- Vascular injury: The obturator vessels are intimately related to the nerve and can be injured during dissection 4
- Lymphocele formation: Extended dissection including the obturator fossa carries approximately 20% risk of lymphocele complications 1