Nutcracker phenomenon resulting in left gonadal vein dilation as a critical vascular consideration prior to lateral lumbar interbody fusion: illustrative case.

backgroundLateral lumbar interbody fusion (LLIF) is a minimally invasive spinal fusion technique utilizing a lateral transpsoas approach to access the anterior column of the spine. Vascular injury is a rare complication but difficult to manage due to the minimally invasive nature of the procedure, making it critical to carefully review preoperative imaging prior to committing to a lateral approach. OBSERVATIONS: A 67-year-old female presented with progressive low back pain and left lower extremity pain and sensory changes. MRI showed a grade 1 L4-5 spondylolisthesis with left-sided neuroforaminal stenosis. The patient was recommended for LLIF; however, on further review of the MRI findings, an abnormally dilated left gonadal vein (GV) was identified along the psoas muscle. Subsequent imaging revealed compression of the left renal vein between the superior mesenteric artery and aorta, causing venous outflow obstruction. Therefore, the surgical approach was changed to avoid potential vascular complications. LESSONS: GV injury is a rare but major complication of lateral spine surgery. This case highlights the importance of careful preoperative imaging and anatomical review as lateral approaches become more common, and acts as a cautionary report for vascular review prior to LLIF. https://thejns.org/doi/10.3171/CASE26180.