Deep Vein Thrombosis in the ED Case 2

A 77-year-old woman was advised to attend the Emergency Department by her GP. She is 2 weeks post total knee replacement on the left side and has had a painful and swollen left leg ever since the surgery. It has worsened in the last 48 hours.

On examination of her leg, the wound has an area of erythema distally, but there is no discharge or collection. Clips have just been removed. Her left leg is swollen from the foot into the upper thigh and her calf is tender. Her left calf is 2cm greater in circumference than her right and there is some pitting oedema. She is apyrexial.

List the differential diagnoses that need to be considered in this lady.

Given the clinical information above, what is her two-level Wells Score?

What is the next most appropriate investigation?