PURPOSE: To investigate the association between the degree of common iliac vein (CIV) compression and the incidence of iliac vein involvement thrombosis (IVT) in patients with infrainguinal deep vein thrombosis (DVT).

METHODS: This was a single center retrospective study. Between January 2015 and July 2023, infrainguinal DVT patients with or without IVT were included. Patient baseline demographics, clinical characteristics, and radiographic variables were collected and analyzed. Univariate analysis followed by multivariate analysis was used for IVT to determine odds ratio (OR) with a 95% confidence interval (CI). The association of the degree of CIV compression and IVT was evaluated by restricted cubic spines (RCS) on a continuous scale.

RESULTS: 222 left-sided DVT patients [140 (63.1%) patients diagnosed with IVT, and 82 (36.9%) without] were included. Univariate analyses revealed a higher prevalence of female gender (55.7 vs. 41.5%, p = .040) and CIV compression among patients with left-sided IVT compared to those without IVT. After adjusting for female gender, a strong positive association between IVT and moderate (compression degree > 50% and ≤ 75%) (adjusted OR 3.75; 95% CI 1.571-8.974; p = .003) to severe (> 75%) (adjusted OR 4.05; 95% CI 1.615-10.134; p = .003) CIV compression degrees remained, indicating moderate or severe compression significantly increased IVT risk. RCS showed that a greater CIV minimum diameter or a smaller compression percentage was negatively associated with IVT incidence at a CIV minimum diameter was > 4.1 mm (p < .001) or compression percentage was < 61.0% (p < .001).

CONCLUSION: Moderate and severe CIV compression were associated with increased IVT risk compared to no or mild compression. A decreasing degree of CIV compression was consistently associated with a decreasing risk of IVT when the minimum diameter was > 4.1 mm or the compression was < 61.0%.