Pleural effusion, in standing position gravitates n the region of

i.e. (Costodiaphragmatic recess: (1658-66 - H17th) (306-8-CMDT-l1)* Most dependent recess of the pleura is the posterior costophrenic angle**. So in pleural effusion this recess would be filled earliest. But at least 100-200 ml of fluid. Would be required to fill this recess before it can be defected on a PA view* The lung is less dense than water and floates on pleural fluid that accumulates in dependent regions* Sub pulmonary fluid may appear as lateral displacement of the apex of the diaphragm with an abrupt slop to the costophrenic sulcus or a greater than 2 cm seperation between the gastric air bubble and the lung.* On a standard upright chest radiograph approximately 75-100 ml of pleural fluid must accumulate in the posterior costophrenic sulcus to the visible on the lateral view and 175-200 ml must be present in the lateral costophrenic sulcus to be visible on he frontal view (307-CMDT-l 1)* Best method to defect minimal pleural effusion decubitus view with a horizontal beam*** Most common cause of pleural effusion is LVF* Most common cause of an exudative pleural effusion developing countries TuberculosisCriteria of Exudative pleural effusion1. Pleural fluid protein / serum protein > 0.52. Pleural fluid LDH / serum LDH >0.63. Pleural fluid more than two thirds normal upper limit for serumCauses of Transudative Pleural Effusion 1. CHF (>90% of cases)2. Cirrhosis with ascitis3. Pulmonary embolization4. Nephrotic syndrome5. Peritoneal dialysis6. SVC obstruction7. Myxedema8. Urinothorax9. Constrictive pericarditis10. Atelectasis (Acute)Chest CT scan may identify as little as 10 ml of fluid