Third mogul sign
The third mogul sign can be seen on frontal chest radiograph in the presence of left atrial enlargement. It refers to an extra mogul or bump along the upper left cardiac silhouette just below the left main bronchus.
The third mogul sign commonly represents the enlarged left atrial appendage, particularly in patients with rheumatic heart disease. Other causes that may also appear as a third mogul on the cardiomediastinal contour include: