A 60-year-old male presents with acute onset unilateral leg swelling, pain, and erythema. He recently had abdominal surgery. Physical examination reveals a swollen, tender, and warm left calf. Which of the following is the most appropriate initial diagnostic and therapeutic step?

✓ Correct Answer: Option B

The patient has signs and symptoms highly suggestive of deep vein thrombosis (DVT), especially post-surgery. A duplex ultrasound is the diagnostic test of choice. Given the high clinical suspicion, therapeutic anticoagulation should be initiated promptly while awaiting or immediately after confirming the diagnosis.