A young man with shortness of breath

A man in his 30s presented to the emergency department with a three week history of chest pain (worse on inspiration), cough, shortness of breath, and discomfort in his left groin. He had been admitted six weeks earlier with deep vein thrombosis of the right femoral vein and cellulitis in the left foot (with a fully sensitive Staphylococcus aureus bacteraemia); he was treated with antibiotics until discharge but was non-compliant with anticoagulation on discharge. He reported weight loss of 5 kg over the past two months. He was an injecting drug user of heroin, most recently using both his groins as injection sites—although he said he previously used most of his other veins—and had been a smoker of 150 g of tobacco (roll-up) a week for 14 years.

On examination, he was alert, had a temperature of 38°C, oxygen saturations 99% on room air, respiratory rate 36 beats/min, pulse rate 91 beats/min, and blood pressure 98/64 mm Hg. He had no palpable lymphadenopathy and no added heart sounds. He had reduced air entry and dull percussion on the left side of his chest. He …