What would cause nonpitting edema in one leg?

I have a patient that has non pitting edema in only his left leg. It's only from the knee down. He says its not painful, but just itches real bad. It goes down if he elevates it. I'm at a loss as to what would cause it except that maybe a lymph node isn't draining. Or maybe a DVT.
Unilateral nonpitting edema is usually from lymphedema, or possibly pretibial myxedema (hyperthroidism) or possible inflammation, maybe gout. Usually nonpitting doesn't respond to elevation of limb. It could also be from cellulitis (causing the itching) or possible insect bite, or allergic reaction.