Formation and disappearance of pocked erythrocytes: studies in human subjects and laboratory animals.

The pocked or "pitted" RBC count is being increasingly utilized as a test of splenic function. Since little is known about patterns of formation and removal of the characteristic organelles in the pocked RBC, we performed serial pocked RBC counts following splenectomy in six patients and in three animal species (dogs, rats, and rabbits). In the patients, pocked RBC counts began to rise within 1 week following splenectomy and reached a plateau (40-60%) by 60-100 days. Similar results were obtained following splenectomy of dogs, except that the plateau value was less. Pocked RBCs in splenectomized rats rose initially, but after the sixth week there was a progressive decline in their numbers; splenosis or accessory spleens were not visualized at autopsy. Rabbits had only a slight and inconsistent rise in pocked RBCs after splenectomy. When the rate of removal of pocked RBCs from the circulation was determined by transfusion of blood from splenectomized dogs in eusplenic animals, the pocked RBC count rapidly decreased within 3 to 6 hours. Pocked RBCs did not disappear when crosstransfused into a splenectomized recipient animal. Prior treatment of the recipient dog with either corticosteroids or vincristine did not affect the pattern of removal of pocked RBCs. We conclude that pocked RBCs rise slowly following splenectomy, disappear rapidly from the circulation in the presence of a normal spleen, and vary in pattern of rise and peak levels following splenectomy of different laboratory animals.