Anatomic evaluation of retroperitoneal organs for lateral approach surgery: a prospective imaging study using computed tomography in the lateral decubitus position.

PURPOSE: The aim of this study is to investigate retroperitoneal organ distribution with the retroperitoneal approach in the lateral decubitus position.
METHODS: We enrolled 100 patients scheduled for lateral approach surgery, including LIF and lateral corpectomy. We performed computed tomography with lateral decubitus positioning (L-CT) to assess the position of the organs, including abdominal aorta, kidney, descending colon, ureter, and gonadal artery. Anteroposterior organ positions were divided into four zones: A, anterior to the anterior margin of the vertebral body; AL, anterior margin to the middle line of the vertebral body; PL, middle line to the posterior margin of the vertebral body; and P, posterior to the posterior margin of the vertebral body. We defined zone PL-P as the "approach zone." Measurements obtained using L-CT were compared with those obtained in the conventional supine position (S-CT).
RESULTS: Retroperitoneal organs in the approach zone significantly decreased in lateral positioning. Eighty-three percent of kidney and 20% of descending colon remain in the approach zone in L-CT. Sixty-six percent of disk levels recorded for the descending colon in zone P in S-CT remained in the approach zone even in L-CT.
CONCLUSIONS: We observed anterior migration in L-CT in all retroperitoneal organs. However, a considerable percentage of kidney and that of descending colon remain obstruent while performing LIF. We discuss that the preoperative imaging evaluation is beneficial, and gentle and meticulous surgical detachment is essential for safe and reliable lateral approach surgery, especially in the case that the descending colon extends outside zone P in S-CT. These slides can be retrieved under electronic supplementary material.