Swelling

I have unexplained swelling in the left leg, ankle and foot.  I was hospitalized and had every test imaginable.  Nothing was there.  My d0Dimer blood test was elevated but no clots were found after extensive CT scans, Ultrasounds and MRI's.  Orthopedic x-rays and test rule out joint issues.  When I rest swelling does go down but upon rising and walking around swelling again.  Any assistance yoyu can suggest would be appreciated.

[Cleveland Clinic]

With a normal MRI and CT scan the likelihood of there being an active clot is essentially zero.  The only thing I can think of is venous insufficiency due to a valve dysfunction.  I would suggest wearing a compression stalking.