Acute congestion may result from active irritation or as the early stage of inflammation.

Passive congestion is common in diseases of the liver associated with engorgement of the portal veins, and to a less degree in chronic heart and lung disturbances. Local congestion is the result of some limited involvement of the mesenteric veins. The veins are swollen and prominent, the mucosa is swollen, edematous, dark bluish in color, and small petechial hemorrhages may be present.