MSFinals-6200

MSFinals-6200

A 72-year-old male comes to the Emergency Department during your night shift complaining of severe pain and discoloration in his right leg. He reports feeling pins and needles in the same leg, and the pain is present even when he is at rest. Upon examination, you notice that his right foot is pale, cold, and painful to the touch. You cannot feel any palpable pedal pulses. The patient has a medical history of ischaemic heart disease, chronic obstructive pulmonary disease, diabetes mellitus, and is a current smoker. What initial investigation should be performed to aid in the diagnosis?