The various forms of pulmonary varices. Report of three cases and review of the literature.

Ture pulmonary varices are congenital local dilatations of a pulmonary vein or veins, with normal or collateral transpulmonary drainage into the left atrium. Pulmonary varices do not cause pulmonary venous hypertension, but existing varices can further become dilated by pulmonary venous hypertension due to mitral valve disease. Embryologically, pulmonary varices may represent residual primitive splanchnic venous components incorporated into the pulmonary venous system, or atresia of an individual pulmonary vein which occurred at a time that enable adoption of unobstructed transpulmonary collateral drainage into the left atrium. True pulmonary varices do not produce symptoms, do not change in diameter over the years, and, usually, do not require treatment.