Automated computed tomography quantification of iliofemoral venous arc length demonstrates left-sided predominance and sex-specific variation.

objectiveIn treatment planning for iliac venous obstruction, iliofemoral venous anatomy is central to procedural planning, but population-level reference data on venous arc length are limited. Arc length, the distance measured along the three-dimensional vessel centerline, reflects the longitudinal course a device must traverse, and is therefore relevant to stent length selection and implant coverage. We used automated computed tomography segmentation and centerline generation to characterize iliofemoral venous arc length and evaluated variation by laterality, age, and sex.

methodsIn this retrospective study, a machine learning (nnU-Net-based) pipeline was used to segment iliofemoral vessels from participant computed tomography scans. Three-dimensional centerlines were generated from these segmentations, and iliofemoral arc length was measured from the iliocaval confluence or aortic bifurcation to the common femoral venous confluence or common femoral bifurcation (encompassing common iliac, external iliac, and common femoral veins/arteries). After quality control and exclusion of patients <25 years, bilateral venous centerlines were available in 711 patients. Right-left arc length differences were compared within patients using paired t-tests. Arterial arc lengths were quantified for comparison. Multivariable linear regression evaluated the relationship between arc length and core covariates such as age, height, and sex.

resultsAmong adults with bilateral venous measurements, iliofemoral venous arc length was 14.8 mm greater on the left side than the right [95% confidence interval (CI), 13.9-15.6; P < .001] corresponding to +7.6% side difference. Height was strongly positively associated with venous arc length (+8.2 mm/10 cm; 95% CI, 7.1-9.3; P < .001). After adjusting for age and height, females had significantly longer venous arc length than males (+5.9 mm; 95% CI, 3.5-8.4; P < .001), with a more pronounced effect on the left side than the right (+7.9 vs +4.4 mm; P < .001). Increased age was associated with a modest decrease in venous arc length (-1.1 mm/decade; 95% CI, -1.8 to -0.4; P = .002).

conclusionsIn this large-scale morphometric study, iliofemoral venous arc length demonstrates meaningful variation by laterality, height, age, and sex, with left-sided predominance and longer height-adjusted venous arc length in females. These population-level reference data suggest that laterality and sex-specific differences may be relevant when considering venous intervention planning, device working length, and stent coverage decisions.