This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory Radiology, Subject name: Radiology
Flat waist sign is seen in 
Select and explain. 
A. Right upper lobe collapse, B. Right middle lobe collapse, C. Left upper lobe collapse, D. Left lower lobe collapse
D: Left lower lobe collapse
Answer: D: Left lower lobe collapse 
Explanation: FLAT WAIST SIGN Flattening of the contours of the aoic knob and adjacent main pulmonary aery. Seen in left lower lobe collapse Caused by leftward displacement and rotation of the hea