OBJECTIVE: To classify the radiographic characterization of the inferior vena cava (IVC) diameter, as well as to quantitatively describe the dimensional alternations in response to variations in filter placement, using cross-sectional computer tomographic venography (CTV) imaging. METHODS: A single-center retrospective study was conducted on eligible patients who underwent CTV of IVC both before and after the placement of spindle-shaped filters, from September 2018 to June 2023. Baseline data, IVC diameter and orientation RESULTS: A total of 70 eligible patients were included, 52 (74.3%) with type 1 IVC, 11 (15.7%) with type 2, 4 (5.7%) with type 3, 3 (4.3%) with type 4, and none with type 5. An accompanying morphological alteration turned IVC into a quasi-round shape with Lin CCC of 0.870, and orientation was significantly altered after filter placement. In patients with type 1, 3, and 4 IVCs, the mean diameter of the IVC increased almost 1.5-fold in the minor axis (95% confidence intervals [CIs]=-7.77 to -5.83, CONCLUSION: The morphology of IVC shifted toward an approximated as circles after filter placement, with greater diameter changes seen in the minor axis compared to the major axis, where filter-related thrombosis most occurs. CLINICAL IMPACT: The findings of this study offer insights into the biomechanical interaction between the inferior vena cava (IVC) and spindle-shaped filters, highlighting the anisotropic dimensional changes triggered by filter placement. The pronounced expansion along the minor axis, where filter-related thrombosis was more frequently observed, underscores a previously underrecognized risk factor for post-implantation complications. These results indicate that perioperative optimization of IVC dimensions and vigilant post-placement monitoring are crucial for improving patient outcomes.