<prompt> If the right cardiac silhouette is obliterated, it means the pathology involves:Right middle lobeRight lower lobeRight atrium of heaRight ventricle of hea  <response>: Right middle lobe opacity illustrates the silhouette sign on the right hea border. The silhouette sign is is commonly associated with alveolar disease. It consists of obliteration of an anatomic border due to direct contact with an alveolar density. It is also associated with pulmonary collapse, masses and pectus excavatum. Ref: Kritek P., Reilly, J.J. 2012. Chapter e34. Atlas of Chest Imaging. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo Eds, Harrisons Principles of Internal Medicine, 18e. 