Correlation of splenomegaly and abnormal neutrophil pooling (margination).

Abstract Splenomegaly causes abnormal pooling of platelets and RBCs, but it has not been clear whether or not the same is true for neutrophils. We have used in vitro labeling of whole blood with DF 32 P to investigate the recovery of labeled neutrophils in circulation immediately after reinfusion into 19 patients with normal-sized to "moderately enlarged" spleens. Twelve patients were neutropenic, and 18 later had a splenectomy. Eleven of these 18 patients were studied by the same technique after splenectomy. Labeled neutrophils which were not recovered were interpreted as being in the "marginal pool." Correction factors for the increased blood volume in splenomegaly were applied. Significant correlations were found between spleen weight or spleen size by external palpation and the marginal pool size. These correlations were evident whether or not blood volume corrections were made. Five patients with moderately enlarged spleens, the largest in the study, had an average of 80% of intravascular neutrophils in the marginal pool as opposed to a normal average of 58%. Following splenectomy, the marginal pool proportion decreased to an average of 45%. Thus the abnormally large marginal pool in splenomegaly can be a significant pathophysiological cause of neutropenia. This cause can be identified by physical examination.