The Dept of Anaesthesia & Intensive Care, CUHK
The most common causes are congestive heart failure, parapneumonic effusions and haemothorax. It is not possible to diagnose the nature of the pleural flood based only on the plain film and ultrasound examination and paracentesis is often required.
In an erect or sitting x-ray the diaphragmatic contour and lateral costophrenic sulcus may be obscured. In a supine patient fluid is usually manifested by a generalized opacity of the lung on the affected side, or may be seen accumulating at the apex (pleural fluid cap).
Left pleural effusion
On the supine chest x-ray up to 400-500ml of pleural fluid can go undetected. On the erect chest x-ray usually only 50-100ml of pleural fluid is likely to go undetected. Remember that the fissures are in continuity with the pleural space. Therefore, fluid can fill and distend the fissures. This phenomenon is often refered to as pseudotumor because of it’s resemblance to a tumor.
February, 2015 unless
otherwise stated. The author, editor and The Chinese University of Hong Kong
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