A 69 year old man presents with acute pain in the left foot for 3 days, which rapidly worsened over time. The pain is present at rest and is not relieved by hanging the foot down.

During the previous year, he experienced 'tightening' pain in the left calf after walking short distances, with complete relief following stopping and resting.

He was diagnosed with diabetes 10 years ago, with satisfactory control. He is a heavy smoker, with a pack history of 30 years.