**3.1 Natural history**

The natural history of venous thromboembolism is variable. There are four potential outcomes when thrombosis occurs. The thrombus can propagate, embolize, organize, or undergo fibrinolysis. Proximal thrombi are more likely to propagate and embolize than the smaller distal thrombi in general. 80% of symptomatic DVTs involve the proximal veins (Conduah & Lieberman, 2007).
