Pulmonary varix is a non-obstructive dilation of one or more pulmonary veins near the left atrium. It is histologically normal.
They are associated with
Acquired heart disease; usually mitral stenosis > regurgitation
Left atrial enlargement
Pulmonary venous hypertension
Radiological findings include an elongated vein in the right lower lobe (inferior pulmonary vein). On CT, the pulmonary vein would demonstrate maximum enhancement during the venous phase.
Pulmonary varix is not clinically significant. It's important not to confuse them with a mediastinal mass.