ABSTRACT
In reading chest radiographs it is important to understand their limitations, basic anatomy and some physiology, and to have a systematic system of scrutiny. Mediastinal visibility is an essential part of chest radiography, since it is only by noting the presence, displacement or absence of the normal lines, that many abnormalities will be detected. Loss of a mediastinal line or organ outline will usually indicate adjacent disease. Reorientation, adjacent consolidation, or air or fluid within major fissures may allow them to be seen on frontal views. The horizontal fissure normally lies at the level of the right fourth costo-chondral junction. Undulation may occur in the horizontal fissure, and this coupled with undulation of the right major fissure may sometimes cause the horizontal fissure to appear to extend posterior to the major fissure. Incomplete fissures may also alter the expected patterns of inter-lobar fluid or air.
