I have a mild pain i can't explain in my lower leg. is there any way to rule out deep vein thrombosis?

ultrasound: There is a blood test that can suggest the presence or fairly certainly determine the absence of a clot, but ultrasound is the usual way to determine if a DVT is present.

Ultrasound. : An ultrasound is the only real test to evaluate for a blood clot.

Yes: Several diagnostic imaging tests can be done to exclude deep vein thrombosis to include ultrasound, venogram(dye study), ct scan or mri(mrv). Ultrasound is the least expensive and can be done quickly. I would suggest you see a vascular specialist or phlebologist(vein specialist). There are other blood tests (d dimer)and noninvasive tests such as a phleborheogram which can be supportive