Clinical presentation

A 79 year old gentleman underwent exploration of a dislocated hip arthroplasty. During surgery, he regurgitated bile stained fluid into his laryngeal mask airway. His chest remained clear, saturation did not fall, and chest radiography immediately postoperatively was unremarkable.

Twelve days postoperatively he developed respiratory distress associated with right sided pleuritic chest pain. Air entry was symmetrical and he was tachypnoeic (respiratory rate 26), hypotensive, and tachycardic (heart rate 140 beats/min). Electrocardiography revealed a right heart strain pattern. Oxygen saturation initially was 80%. Arterial blood gases on initial oxygen therapy and their subsequent improvement are given in table 1.

At medical review, chest radiography was interpreted as right lower zone shadowing and a preliminary diagnosis of postoperative pulmonary embolus was postulated, treatment with oxygen continued, and low molecular weight heparin was commenced.

An urgent computed tomography (CT) scan of the thorax was arranged and the scanogram revealed the true diagnosis.

Question

What does the CT scanogram show and what is the underlying cause?

See page 1286 for answer

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