Deep vein thrombosis may not cause any symptoms, in which case, it are diagnosed based on certain tests.
DVT may not display any symptom or may cause swelling and pain in the concerned leg. DVT is a serious condition but its complication --pulmonary embolism- -is life-threatening.
Symptoms of PE include chest pain and shortness of breath. In extreme cases, the condition may be fatal.
Diagnosis usually involves duplex ultrasound which is a special type of ultrasound scan done of the leg. If this test is negative and the doctor is still suspicious, then further diagnostic tests, such as venography, may be done. This test uses an X-ray image to track a special dye injected into the leg’s deep vein.
If DVT is being merely considered as an option, then a blood test called a D-dimer may be done.
DVT Risk Factors Related to Travel – Factors that increase the risk of DVT during travel are:

Pregnancy

Certain medications /oral contraceptives

Some medical conditions

Clotting abnormalities

Obese person travel without stretching legs

Frequent travelling long distance Travelling in cramped position

Obese person

Lowered air pressure/low oxygen/low humidity