Chest Imaging

Bare area diaphragm sign

feature that is helpful in distinguishing pleural fluid from ascites at CT. The peritoneal reflections of the liver leave a bare area at the posteromedial surface of the right lobe between the superior and inferior layers of the coronary ligament. Since the bare area is extraperitoneal, ascites does not normally collect at this site. Pleural fluid collects along the full width of the hemidiaphragm within the costophrenic recesses posterior to the liver. Therefore fluid which is posteromedial to the liver is due to a pleural effusion rather than ascites unless the patient has no bare area such as after liver transplantation.

CF - HM