Look, I'm John Snow on most of this diagnosis stuff. I know nothing. But a couple of observations:
1. sonographers, I respect them but they can be pretty silly sometimes
But over something other than medical things like in your case. They wouldn't have been involved in your diagnosis. Just getting the imaging.
2. Was this guy a cardiologist?
3. I don't really understand the issue for the hospital in x-ray for the clot. I would guess that venous x-ray is less intrusive than venous sonogram. Then again if you've had the sonogram would an x-ray have added any information, or changed your management?
4. That last one is my area of concern - How will the radiation exposure change the management of the condition?
Anyway for your own interest you might like to have a play around with the Diagnostic imaging pathways that they use in Western Australia (also adopted by Dubai)
IMAGING PATHWAYS
I don't know any of your details, but if I look at DVT arm or leg ultrasound is pretty much the recommended imaging option. (look at Cardiovascular and then DVT options). They only suggest venography if there is a technical difficulty with ultrasound of the arm.
Or perhaps looking at the imaging pathways is a stupid suggestion, in which case ignore it.
BTW being respectful and responsive doesn't mean they can't do stupid things. Everyone has brain fades. What is probably more important is that they know when they don't know and seek help. That they referred you to this guy is another point in their favour, not his.