Leg thrombosis can be detected by examining the patient, by ultrasound and, if necessary, by CT. In case of deep vein thrombosis of the lower extremity, the lower extremity will show swelling, slightly elevated skin temperature and flushing, and the swelling will increase with activity, and pain will occur. If the lower extremity is arterial thrombosis, it will show pallor of the skin, decrease in skin temperature, abnormal skin sensation, and loss of pulse. The thrombosis of arteries or veins can be clearly seen by ultrasound. If ultrasound is not able to make a complete diagnosis, MRI or CTA can be used to further clarify the diagnosis.