When we cut our finger and blood is exposed to air, it forms a blood clot, saving us from bleeding. Sometimes we form a form a blood clot within a blood vessel (deep vein thrombosis), which can cause pain and swelling. If some of the blood clot separates it can reach the lung causing a pulmonary embolism.
There are a number of ways to assess the possibility of a DVT, D-dimers and blood flow (Doppler) assess of the legs or area causing concern. If a DVT is diagnosed an anticoagulant is used to reduce the risk of more clots and manage the current DVT.