PB1460 - Venous anomalies – an under-recognised but important cause of venous thromboembolism (VTE)

Background: Venous anatomical variants, such as May-Thurner syndrome (MTS) and inferior vena cava (IVC) variants, increase risk of VTE but are under-recognised despite affecting management options including endovascular intervention.

Aims: To identify the incidence of anatomical variants in deep vein thrombosis (DVT) cases involving the iliofemoral, bilateral lower limb veins or IVC.

Methods: DVT cases were identified retrospectively from Alfred Health medical records using discharge ICD-10 codes between January 2014 and December 2021. Proximal DVT (excluding popliteal vein), bilateral lower limb DVT or IVC thrombus cases were included based on radiology findings (Figure 1). Demographic and clinical data were also obtained. Ethics approval was granted by our institutions Ethics Committee (approval 460/22).

Results: Over an eight-year period, there were 1873 DVT cases, with 315 meeting inclusion criteria diagnosed by ultrasound (92%), CT scan (5%), or formal angiography (3%). The mean age was 59 years, and 196 (62%) were male. 221 (70%) were provoked and 157 (50%) had risk factors such as malignancy (21%) or previous VTE (19%)
Twelve cases of anatomical variants (3.8%) were identified; ten MTS and two hypoplastic IVC variants. Compared to all DVT cases, they were more frequently unprovoked (67% vs 30%), younger (mean age 38 vs 59 years), female (58% vs 38%) and had a significant family history (25% vs 4%) (Figure 2). MTS/IVC variants were more likely to receive interventional management, such as catheter directed thrombolysis (58% vs 7%) or angioplasty (58% vs 7%), and to recommend indefinite anticoagulation (83% vs 30%).

Conclusion(s): We found 3.8% of all proximal DVTs or IVC thromboses had an anatomic variant, but in females under 50 years, it was 17%. These cases often required interventional management and long-term anticoagulation to prevent recurrence.
Our results suggest that further investigation for anatomical variants should be considered in these high-risk patients as this significantly impacts management.