. If the right cardiac silhouette is obliterated, it means the pathology involves:
Right middle lobe An intra-thoracic radio-opacity, if in anatomic contact with a border of hea, aoa or diaphragm, will obscure that border. This is known as silhouette sign. An intra-thoracic lesion not anatomically contiguous with a border or a normal structure will not obliterate that border. When examining the lung fields of a normal CXR, the silhouettes of the hea borders, the ascending and descending aoa, the aoic knob and the hemidiaphragms should be clear. Obliteration of any of these silhouettes by a radio-opacity can be caused by infection in the lung, blood, pus, etc. All of these silhouettes, or structures, are in contact with a specific poion of the lung. Therefore, by determining exactly which structure is obliterated, you can determine where the lung pathology is located. Silhouette/Structure Contact with lung Upper right hea horderlascending aoa Anterior segment of RUL Right hea border RML (medial) Upper left hea border Anterior a sement of LUL ,,, Left hea border Lingula (anterior) Aoic knob Apicoposterior segment of LUL Hemidiaphragms Basal seg.of lower lobes
Right middle lobe
Right lower lobe
Right atrium of hea
Right ventricle of hea