The role of CT pulmonary angiography in the investigation of unilateral pleural effusions.

BACKGROUND Pulmonary embolism (PE) is frequently cited as a common primary cause of unilateral pleural effusion, but in clinical practice appears to be uncommon. OBJECTIVES In order to evaluate this observation, CT pulmonary angiography (CTPA) was performed in consecutive patients presenting to a single centre with a new uninvestigated unilateral pleural effusion and no clear cause and was supplemented by delayed-phase thoracic CT, optimized for visualization of the pleura. METHODS All patients underwent standard clinical assessment and pleural investigations in line with recent national guidelines and were followed up for a minimum of 1 year or until histological/microbiological diagnosis. RESULTS One hundred and fifty patients were recruited, and of these, 141 had a CTPA. PEs were detected in 9/141 (6.4%) patients, and of these, 8/9 were subsequently diagnosed with pleural malignancy. In only 1 case was PE clinically suspected and in no case was PE the primary cause of effusion; 9.8% (8/82) of patients who were ultimately diagnosed with pleural malignancy had PE at presentation. CONCLUSIONS This study indicates that PE is a frequent concomitant finding in patients with malignant effusions but uncommon as a primary cause of unilateral effusion. In addition, it highlights the known difficulty of clinical diagnosis of PE in the context of malignancy. In view of this, we recommend that CTPA combined with pleural-phase thoracic CT should be considered at presentation when investigating patients with suspected malignant pleural effusion.