Left atrial enlargement is seen in -

Ans. is 'a' i.e., Mitral stenosis Radiological signs of mitral stenosisDue to left atrial enlargement :- Straightening of left heart border, elevation of left main bronchus with widening of carina, double atrial shadow (Double density sign), posterior displacement of esophagus on barium swallow, Prominent posterosuperior part of cardiac shadow.Due to pulmonary venous hypertension :- Diversion of blood flow from the lung bases to the upper zone (cephalization of pulmonary vascularity), pulmonary hemosiderosis, peribronchial cuffing, Kerley B lines and some times Kerley 'A' lines, perihilar haze, alveolar edema, small pleural effusion, pulmonary ossicles, fine punctate calcification in lung.Due to elevated pulmonary hypertension :-Enlargement of central pulmonary vessels with peripheral prunning.