Deep Vein Thrombosis in the ED Case 3

A 54-year-old male presents with an 8 hour history of pain in his left calf on walking. He thinks he may have strained a muscle and is only able to manage about a few yards before he stops. He smokes 20 cigarettes a day.

On examination there does not appear to be any warmth or swelling of the left leg. It appears slightly pale and is diffusely tender to palpate, although there is no specific calf tenderness. He has reduced sensation over his forefoot and some weakness in his toes.

What is the most likely diagnosis?

What would be the most appropriate investigation in the ED to further evaluate his peripheral pulses?