Deep vein thrombosis or DVT could start showing itself with sudden pain in the calf or thigh muscles. One calf may be an inch more swollen than the other. DVT treatment from a doctor should be sought immediately if you find swollen veins along with pain in a limb. In this condition, a blood clot otherwise known as a thrombus is formed in a deep vein. This condition commonly affects the leg veins, like the popliteal, femoral or the deep veins in the pelvic region. This condition can be fatal if the clot comes loose and enters the blood flow. It can travel to the heart or lungs and lodge itself there resulting in immediate death of the patient.