Chronic venous congestion is a condition seen mainly in case of reduced cardiac output or blockage in the venous outflow of an organ, mainly liver, spleen, kidneys, lungs, etc. The blood vessels are engorged; there is hemorrhage into the interstitium; the organ is congested and oedematous and on prolonged standing, as in case of heart failure; macrophagic infiltration, that take up the celluar debris, haemoglobin, etc. The haemoglobin is converted into haemosiderin inside. These cells are known as "heart failure cells".
Gross appearance of lung in chronic venous congestion of the lungs is rusty brown due to brown induration of the lungs.