Erythrocyte pooling and sequestration in enlarged spleens. Estimations of splenic erythrocyte and plasma volume in splenomegalic patients.

Abstract

Erythrocyte pooling and sequestration in the spleen were studied in 73 patients with splenomegaly due to various haematological disorders using 51Cr‐labelled autologous erythrocytes and surface counting. Arbitrary values for the accumulation of activity in spleens of different sizes were obtained by correcting measured splenic surface activities (correction factors have been experimentally estimated). Absolute values for the splenic content of 51Cr and 125I were obtained by comparative surface activity measurements over the enlarged spleen and a model of the spleen charged with a known amount of activity. In this way the splenic erythrocyte and plasma volume may be estimated.In cases of pronounced splenomegaly without complicating immunohaemolysis the splenic erythrocyte pool (splenic erythrocyte volume/total erythrocyte volume) increases with increasing splenic weight, apparently independently of the underlying haematological disorder, the splenic erythrocyte content varying only with body haematocrit. Hyperhaemolysis is a regular finding in enlarged spleens. The splenic erythrocyte sequestration rate increases with increasing splenic erythrocyte pool and is much higher in myeloproliferative than in lymphoproliferative disorders. The total plasma volume is expanded in splenomegalic patients, but the splenic plasma volume constitutes only a minor part of this increment.The anaemia of splenomegalic patients is a consequence of splenic erythrocyte concentration and hypersequestration combined with expansion of the plasma volume. Frequently the total erythropoietic capacity is reduced. Splenectomy is regularly followed by an increased venous haemoglobin concentration.