Pathophysiology.—Pulmonary blood flow redistribution refers to any departure from the normal distribution of blood flow in the lungs that is caused by an increase in pulmonary vascular resistance elsewhere in the pulmonary vascular bed.
Radiographs and CT scans.—Pulmonary blood flow redistribution is indicated by a decrease in the size and/or number of visible pulmonary vessels in one or more lung regions (Fig 59), with a corresponding increase in number and/or size of pulmonary vessels in other parts of the lung. Upper lobe blood diversion in patients with mitral valve disease is the archetypal example of redistribution (112,113). [Fleischner Society]