Left Common Iliac Vein Compression in Patients with May-Thurner Syndrome: A 10-Year Retrospective Study in an Australian Cohort

Objectives: This study aimed to assess what diameter constitutes clinically-significant left common iliac vein (LCIV) compression in patients with May-Thurner syndrome (MTS). Materials and Methods: Nineteen patients with MTS were over a 10-year period. Minimum LCIV diameter was compared to 100 asymptomatic controls and 27 age- and gender-matched controls. Results: Mean LCIV diameter in MTS group was 3.82 mm (standard deviation [SD] 1.38), control group (mean 7.17 mm SD 3.19, P < 0.0001), and matched control group (mean 6.86 mm SD 3.03, P = 0.007). Statistical threshold analysis showed in MTS patients, a LCIV diameter of 4.7mm or less had an 87.5% sensitivity and 72.7% specificity for the diagnosis. Conclusions: Patients with MTS had a minimum LCIV diameter threshold of 4.7mm, and this can be used in correlating the diagnosis of MTS on computed tomography. However, minimum diameters less than 4.7 mm are also seen in the general population and as such compression alone does not constitute a diagnosis of MTS.