Severe compression of left iliac vein is a protective factor for the risk of inferior vena cava thrombosis.

Objective: The purpose of this study is to evaluate the association between left iliac vein (LIV) compression and inferior vena cava thrombosis (IVCT) in patients with LIV involvement of deep vein thrombosis (DVT).

Methods: A total of 263 consecutive patients with DVT were reviewed retrospectively and divided into a group with IVCT and a group without IVCT. The influences of LIV smallest diameter and percentage compression on the risk of IVCT were investigated using logistic regression analysis.

Results: The mean age of patients with IVCT was significantly younger than that of patients without IVCT (55.5 ± 1.8 vs 62.7 ± 1.1; P = .001). The percentage of provoked DVT in patients with IVCT was higher than that in patients without IVCT (67.1% vs 48.2%; P = .01). The smallest diameter of the LIV in patients with ICVT was larger than that in patients without IVCT (4.1 ± 0.3 vs 2.5 ± 0.2; P < .001). The mean percentage compression of LIV in patients with IVCT was significantly lower than that in patients without IVCT (63.5 ± 2.2 vs 74.3 ± 1.3; P < .001). Age was associated with a decreased odds of ICVT (odds ratio [OR], 0.965; 95% confidence interval [CI], 0.965-0.985; P = .001). Provoked DVT was associated with an increased odds of ICVT (OR, 2.011; 95% CI, 1.070-3.782; P = .03). LIV compression was associated with a decreased odds of ICVT for each 1-mm decrease in smallest diameter of the LIV (OR, 0.717; 95% CI, 0.627-0.820; P < .001), and for each 10% increase in percentage compression of the LIV (OR, 0.715; 95% CI, 0.612-0.835; P < .001).

Conclusions: For LIV involvement in patients with DVT, patients without IVCT had more severe LIV compression than patients with IVCT. Severe LIV compression may be a protective factor for the risk of IVCT.