Figure 4c. Sagittal CT images demonstrate a common ostium of the left pulmonary veins, and solid arrows show the left superior and inferior pulmonary veins. (a) Left superior and inferior pulmonary veins approach the left atrium (LA) separately. (b) Left superior and inferior veins unite before entering the left atrium. (c, d) Veins enter the left atrium through the same ostium (open arrow).