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How is deep vein thrombosis diagnosed (DVT)?
The diagnosis of superficial thrombophlebitis is often made by the health
care professional at the bedside of the patient, based upon the physical
DVT usually is diagnosed with ultrasound.
Ultrasound is now the standard method of diagnosing the presence of a deep vein thrombosis.
The ultrasound technician may be able to determine whether a clot exists, where it is located in the leg, and how large it is. Ultrasounds can be compared over time to see whether a clot has grown or resolved.
Ultrasound is better at "seeing" the veins above the knee as compared to the
small veins below the knee joint.
D-dimer is a blood test that may be used as a screening test to determine if a blood clot exists. D-dimer is a chemical that is produced when a blood clot in the body gradually dissolves. The test is used as a positive or negative indicator. If the result is negative, then
in most cases no blood clot exists. If the D-dimer test is positive, it does not necessarily mean that a deep vein thrombosis is present since many situations will have an expected positive result (for example, from surgery, a fall,
in cancer or in pregnancy). For that reason, D-dimer testing must be used selectively.
Other tests for DVT
Venography, injecting dye into the veins to look for a thrombus, is not usually performed any more and has become more of a historical footnote.
Other blood testing may be considered based on the potential cause for the deep vein thrombosis.