To diagnose thrombophlebitis, your doctor will ask you about your discomfort and look for affected veins near your skin's surface. To determine whether you have superficial thrombophlebitis or deep vein thrombosis, your doctor might choose one of these tests:
Ultrasound. A wandlike device (transducer) moved over the affected area of your leg sends sound waves into your leg. As the sound waves travel through your leg tissue and reflect back, a computer transforms the waves into a moving image on a video screen.
This test can confirm the diagnosis and distinguish between superficial and deep vein thrombosis.
Blood test. Almost everyone with a blood clot has an elevated blood level of a naturally occurring, clot-dissolving substance called D dimer. But D dimer levels can be elevated in other conditions. So a test for D dimer isn't conclusive, but can indicate the need for further testing.
It's also useful for ruling out DVT and for identifying people at risk of developing thrombophlebitis repeatedly.