What is the pathogenesis of the formation of the pigment in the lungs? Congestive heart failure Pulmonary congestion Leakage of red blood cells out of congested pulmonary capillaries into alveoli Phagocytosis of red blood cells in alveoli by pulmonary macrophages Conversion of hemoglobin in red blood cells into hemosiderin in macrophages Back up of blood into lungs .