(Click the link to comment and to vote – voting not working through email, sorry!)

You are seeing a 17-year-old boy with one day of right calf pain and swelling. The day before onset of his symptoms, he was helping with a kitchen remodel and tried to remove a support beam by kicking it multiple times. He continued to help, and it wasn’t until the next morning that he noticed his symptoms. He has no significant PMH. He has taken no medications. He has had no recent travel, illness, or other trauma. On exam, he is afebrile, HR 65, RR 18, BP 140/80, weight 135 kg, BMI 42. His right calf circumference measures 1.5 inches more than his left. His calf is not particularly tender to palpation, and there is no redness or warmth. His leg is not swollen above the knee. He has normal sensation distally and normal color. He is able to walk without a limp but has pain with walking. He has no pitting edema. 

What is the best next test?