Dick Blast,

Thanks for your question.

Diagnosing a blood clot in the leg can be challenging.  It requires a good history, examination, and testing (venous Doppler) of the leg to  be sure of the diagnosis.  Of the three (history, exam, testing), studies have shown that examination is the least reliable.  If there is any suspicion of a blood clot, a Doppler should be done to rule out, or rule in this diagnosis.  Though clots below the knee have less risk of breaking off and traveling to the lung, they can propogate (increase in size by forming more clot on itself) and pose a greater risk with time. 

Because of the potential life threatening effects of a blood clot that has broken off and traveled to the lung (pulmonary embolus), doctors are very aggressive when there is even a remote possibility of this problem.  Should it be present, then earlier treatment with blood thinners will lower the risk for embolization. 

Call your doctor for an appointment to be seen as soon as possible to have this evaluated.

Best wishes.

Martin Cane, M.D.