Measurement of splenic function in humans using heat damaged autologous red blood cells.

Functional hyposplenism, a clinical entity which has only recently been recognised, is usually assessed quantitatively by the rate of clearance of radiolabelled heat damaged erythrocytes (HDE) from the circulation. Based on recent observations on the kinetics of HDE, we have developed a 3 compartmental model of HDE distribution between the spleen and blood, and calculated, in a large series of clearance curves, splenic blood flow, HDE intrasplenic transit time and splenic HDE extraction ratio. Transit time (about 15 min) was of the same order as platelet transit time and extraction ratio (about 35%) was similar to that recorded in animals. Thr relationships between blood flow, transit time and extraction ratio provided evidence in support of 2 separate functional compartments, of which only one was engaged in phagocytosis, present within the spleen.