Polycythemia vera verified by second opinion. + crohns. unilateral calf swelling. unilateral superficial vein. d-dimer + us normal. get venogram?

Hard to know: The correct answer would depend upon your Wells score or some other method of predicitng the pre test probability of DVT. If one were to assume that this is a high pretest scenario then venogram would be the most appropriate next step. IF this would be considered a moderate risk scneario than a repeate US in several days time would be warrented.

Difficult to know: Polycythemia vera and Chrons are both risk factors for DVT . Also your sign and symptoms are suspicious for DVT. Venous Doppler US for a single exam may miss small DVT especially in the calf. D dimer if normal pretty sensitive. Many options repeat: Ultrasound and possibly d dimer, venogram [but these are not done much now], follow closely. Recommend close follow up with your doctor/ vein expert.