John Owens is a 54-year-old man who has been sent to the Emergency Room (ER) by his PCP because of a painful swollen right leg. You are asked to see him. John attends alone. He describes his symptoms: “I woke up three days ago and thought my right leg felt a bit tender in the calf area, but thought nothing of it. I went to work as usual. By the end of the day I noticed my ankle was a bit puffy. Next day I woke up and it was a bit worse. But this morning my entire lower leg was swollen and painful. I went to see my PCP who arranged for me to come here. I feel otherwise well in myself.” John has no past medical history, is not taking any regular medication, and is not allergic to anything that he knows of. He runs his own import-export business, and lives with his wife and two teenage children and a Labrador. He is normally quite active, going for long hikes at weekends. He has never smoked, and drinks around 2 bottles of wine a week. He has not been doing anything differently in the last few months –
