Migration and embolization of macrophages to the lung--a possible mechanism for colloid uptake in the lung during liver scanning.

Estrogenic stimulation of the RES in animals will result in the mobilization of large numbers of phagocytic cells from their natural sites of storage, chiefly the liver, spleen, and bone marrow, into the intravascular space. These cells are trapped in the pulmonary capillary bed and retain their ability to phagocytize colloidal particles. This is suggested to be the mechanism whereby increased lung uptake of colloidal radiopharmaceuticals is observed in some patients with liver diseases or other conditions stimulating the RES. It is further postulated that the known increase of estrogenic hormones in some patients with liver disease may be the in vivo stimulation resulting in increased mobilization of RES cells to the lung and subsequent isotope entrapment. It is possible that prognostic information can be obtained from this finding; however, its exact significance cannot be determined from this present study.