Q. Atypical Distribution of Pleural Fluid?

i) Lamellar effusion: These are shallow collections of fluid between the chest wall and the lung surface.

ii) Subpulmonic effusion: Fluid accumulating between the lung and the diaphragm will cause the contour of the "diaphragm" to be altered, its apex being more lateral than expected. There may be associated blunting of the CP angle. On the left side, a subpulmonic effusion may
result in an increased distance between the fundic air bubble and the lung base.

iii) Loculated effusion: Fluid may be loculated along the lung periphery due to fusion of the visceral and parietal pleura. These collections often have a biconvex shape and when viewed in profile have a sharp outline, with tapered margins forming an obtuse angle with the chest wall. Fluid may be loculated in the interlobar fissures, most commonly seen in heart failure. Fluid in the horizontal fissure is well defined and more easily recognized to be an interlobar effusion. In the major fissure, PA and lateral views may be necessary to make the diagnosis. Typically, these collections disappear rapidly after treatment for heart failure, and are known as pseudo or vanishing tumours.