Cardiac rotation in left lower lobe collapse. "The flat waist sign".
Some cases of left lower lobe collapse show slight right anterior oblique rotation of the heart, manifested by loss of the concavity of the left heart border on a perfectly symmetrical posterior-anterior or anterior-posterior projection. This is a useful differential diagnostic sign, because it is not present when the left lower lobe is compressed secondary to left upper lobe emphysema.
D000328:Adult; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging*; D006801:Humans; D008171:Lung Diseases / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011012:Pneumomediastinum, Diagnostic; D011859:Radiography