Erythrokinetic Studies as a Guide to the Value of Splenectomy in Primary Myeloid Metaplasia

S ummary . Red cell survival, plasma volume and erythrokinetic studies were carried out in 13 patients with progressive myeloid metaplasia. The patterns obtained were extremely variable. The majority had a haemodilutional anaemia, due to expansion of the plasma volume, which showed a rough correlation with splenic size. Although most patients showed evidence of haemolysis, only two had a severe haemolytic anaemia. Eight cases were selected for splenectomy; the best results were obtained in those in whom medullary erythropoiesis was still demonstrable by ferrokinetic studies pre-operatively. In another two cases the spleen appeared to be the principal organ of erythropoiesis. Patients who had a haemodilutional anaemia pre-operatively showed a substantial contraction in the plasma volume after splenectomy and, although this may not occur immediately after operation, it appears to be of long duration. It is suggested that the possibility of splenectomy be considered at an earlier stage in the evolution of the disease than has previously been customary.