Lateral Transpsoas Approach to the Lumbar Spine and Relationship of the Ureter: Anatomic Study with Application to Minimizing Complications.

BACKGROUND: Complications from lateral lumbar interbody fusion procedures range from neurologic deficits to organ and blood vessel injuries. Injury to the ureter has been reported though uncommon. The present study was performed to elucidate the anatomic relationship of the ureter to this surgical approach.

METHODS: Eight adult cadavers (16 sides) were placed in the full lateral position, and the distal ureter was cannulated with a metal wire that was passed up to the kidney. Fluoroscopy was used to establish the position of the ureter in relation to the bony anatomy in this region.

RESULTS: In the lumbar region, there was a posterior to anterior course of the left and right ureter. From the direct lateral position, the ureter was found to lie at or posterior to the anterior edge of the lumbar vertebral bodies. On 87.5% of sides, the ureter was on average 2.5 cm posterior to the anterior border of the vertebral bodies at L2, 3 cm posterior at L3, 1.0 cm posterior at L4, and on the margin of the anterior vertebral bodies at L5. In general, the ureter, from a lateral perspective, crossed the posterior third of the upper lumbar vertebrae, approached the middle third at L3, and reached the anterior third at L4/L5 before descending into the pelvis.

CONCLUSIONS: Owing to the proximity of the ureter to the lumbar vertebral bodies, it is imperative to verify that this structure is not in the surgical trajectory during lateral lumbar interbody fusion procedures if injury is to be avoided.