Unilateral vascular plethora--a sign in advanced unilateral basal bronchiectasis

Unilateral basal bronchiectasis results in a regional high vascular pressure and the flow of blood is thereby diverted to the uninvolved portion of the lung through bronchopulmonary anastomoses. Unilateral plethora of the upper lobe vessels in significant basal bronchiectasis of the same lung constitutes an important additional sign in the recognition of bronchiectasis on the plain chest radiograph. Attention is drawn to the fact that this will not occur if the adjacent lung is compromised by a related or unrelated disease process.