High-risk features of superficial vein thrombosis
| Extensive superficial vein thrombosis (> 5 cm) |
| Involvement above the knee, particularly if 3 cm or less from the saphenofemoral junction |
| Severe symptoms |
| Involvement of the greater saphenous vein |
| History of venous thromboembolism |
| Active cancer |
| Recent surgery |
Based on information in references 1, 15, and 16.