Abstract: Objective　To measure the distance between the abdominal aorta and the left psoas major (DALP) at different levels based on CT images and analyzed its influential factors.　Methods　The CT and clinical data of 116 normal adults were retrospectively analyzed. The following measurements were taken: DALP, diameter of the left psoas major, cross-sectional area (CSA) of the psoas major, aortic diameter, transverse diameter and area of the L2 vertebral body, thickness of anterior abdominal wall fat at L2 and navel level, subcutaneous fat area (SFA), visceral fat area (VFA) at L2 and navel level. Additionally, VFA/SFA ratios were calculated at both L2 and navel levels. The radiographic density, density standard deviation and radiographic density ratio (RDR) of the left psoas major muscle at three intervertebral disc levels of L2-L5 were measured in 82 patients. The correlation between the DALP and other data at three intervertebral disc levels of L2-L5 was analyzed, and the regression equation was calculated.　Results　The DALP decreased from level L2 toL5. Age was positively correlated with DALP at L2-L5 disc level (all  P<0.01).The DALP at the L2-L3 disc level was negatively correlated with the CSA of the psoas major at the L2-L3 disc level (P<0.01), and positively correlated with the VFA/SFA at L2 level (P<0.05). The DALP was negatively correlated with the CSA of the psoas major at the L3-L4 disc level (P<0.01), and positively correlated with the VFA/SFA at L2 level (P<0.01).  The DALP was negatively correlated with the CSA of the psoas major at L4-L5 disc level (P<0.01), and positively correlated with the VFA/SFA at L2 level (P<0.05).　Conclusions　On CT images, the distance between the abdominal aorta and the left psoas major was influenced by age, CSA of the psoas major and the VFA/SFA at L2 level. Preoperative CT examination is of great significance in guiding the OLIF operation.

Key words: CT,  ,  , Abdominal aorta,  ,  , Psoas major,  ,  , Influential factors,  ,  , Distance