Variations in the iliolumbar vein during the anterior approach for spinal procedures.

Study Design: Retrospective study from data from a single access surgeon at 2 hospitals.

Objective: To increase the surgeon's awareness of iliolumbar vein (ILV) variants during the anterior approach to the lumbar spine.

Summary Of Background Data: Although there are many advantages to using the anterior approach, serious risks are involved, namely, vascular injury. The ILV is especially vulnerable when exposing the L4 and L5 vertebrae, and its ligature is recommended to avoid massive hemorrhage from its disruption. Cadaver studies on ILV variants have mainly analyzed drainage patterns. To our knowledge, however, no studies on ILV variants have been conducted on live humans during anterior spinal surgical procedures.

Methods: A total of 159 patients who underwent anterior spinal surgery of at least the L4-L5 levels were included. Cases not involving the L4-L5 level were excluded. Frequency of anomalous ILVs and their possible association with diagnosis (spondylolisthesis, herniated nucleus pulposus, degenerative disc disease, and stenosis), sex, comorbidities, and pelvic history was evaluated. ILV was classified into 5 types: type 0 (missing ILV), type 1 (single ILV), type 2 (2 ILVs), type 3 (3 ILVs), and type 4 (>3 ILVs).

Results: Most patients had a single ILV (73%, N = 116). Multiple ILVs were found in 25.8% of cases: 27 cases (17%) for type 2, 11 cases (6.9%) for type 3, and 3 cases (1.9%) for type 4. A higher frequency of multiple ILVs was found in males (32%) than in females (19.2%) (P = 0.034). Diagnosis, comorbidity, and pelvic surgical history were not associated with the number of ILVs.

Conclusion: The high frequency of multiple ILVs found during the anterior approach is crucial knowledge for access surgeons, as it will help them anticipate such anomalies and thus avoid the potentially catastrophic complications of an avulsion of an unexpected extra vein.