Splenic Red Cell Pooling in Hairy Cell Leukaemia

The splenic red cell volume has been measured directly by an isotope method with quantitative scanning in 10 patients with leukaemic reticuloendotheliosis (hairy cell leukaemia). The volume ranged between 211 and 726 ml (mean 410 ml, SD 158) and this constituted 15–48% (mean 28.1%, SD 9.5) of the total circulating red cell volume. This is an exceptionally large pool when compared with that found in myeloproliferative and lymphoproliferative disorders with the same degree of splenomegaly. It is consistent with the histological features which show marked red cell accumulation in the splenic cord areas. The red cell pooling in the spleen thus appears to be a significant factor in the anaemia and there was fairly good correlation between the percentage of improvement in the anaemia and the percentage of red cell volume contained in the spleen. By direct measurement of the splenic red cell pool, it is possible to predict the extent to which splenectomy will benefit the anaemia and this may also provide an indirect measure of the extent of bone marrow dysfunction in the causation of the anaemia.     

Blood Volume Changes in Splenomegaly

S ummary . Blood volume changes have been measured in 65 patients with splenomegaly due to a miscellany of causes. The red-cell mass is often normal despite the fact that anaemia is present, and the anaemia is in part due to sequestration of red cells in a splenic pool and haemodilution of the red cells in an expanded plasma volume. Both factors may be relieved by splenectomy although the ultimate prognosis is dependent on the primary disease present.     

The Body Hematocrit/Venous Hematocrit Ratio and the "Splenic Reservoir"

1. Red cell volume and plasma volume were measured by the radioactivesodium chromate and the chromic chloride method respectively in 37 patients.

2. The body hematocrit/venous hematocrit (BH/VH) ratio was found tobe constant in normal subjects and in patients in whom there was neithersplenomegaly nor edema. The ratio was 0.896 ± 0.039.

3. In splenectomized patients the BH/VH ratio was normal indicating thatin man, in normal conditions, the spleen does not have the function of asignificant blood reservoir with raised cell/plasma ratio.

4. In patients with splenomegaly the BH/VH ratio was found to be significantly increased in direct proportion to the degree of splenic enlargement,indicating an increased concentration of erythrocytes in the enlarged spleen.

5. In the presence of extravascular fluid retention caused by prolongedprednisone treatment the BH/VH ratio was lower than normal.

6. It was concluded that in patients with splenomegaly or edemameasurement of either red cell volume or plasma volume alone in conjunctionwith the "corrected" venous hematocrit does not permit valid assessment ofthe non-measured parameter nor of the total blood volume.

Submitted on June 12, 1960 Accepted on August 2, 1960     

Erythrocyte Pooling and Sequestration in Enlarged Spleens: Estimations of Splenic Erythrocyte and Fiasma Volume in Splenomegalic Patients

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.     

Hypersplenism and splenectomy in lymphoproliferative and myeloproliferative disorders

Splenic pooling of red cells and an expanded plasma volume are considered to be among the major mechanisms responsible for the anaemia in hypersplenism. In those conditions in which massive splenomegaly is associated with various degrees of marrow failure, diagnosis of the cause of anaemia may be difficult. A simple technique was used to estimate the degree of hypersplenism, from red cell mass data, in 94 patients with unequivocal lymphoproliferative or myeloproliferative disorders. The splenic effect was found to correlate well with both the size of the spleen (r = 0.75-0.90) and the actual red cell mass (0.79), and was abolished by splenectomy. Clinical data is also presented on 43 of these patients who underwent splenectomy. The incidence and type of complications, survival figures, and possible criteria for patient selection are discussed.     

Studies of Splenic Function in the Myeloproliferative Disorders and Generalized Malignant Lymphomas

The relative importance of splenic red-cell pooling, sequestration and cell destruction in the causation of anaemia has been studied in 29 patients—16 with generalized lymphoproliferative disease, 12 with myeloproliferative disease and one with idiopathic autoimmune haemolytic anaemia.
A scanning method with [¹¹C]carbon monoxide was used for direct in vivo measurement of splenic red-cell volume, and the spleen was delineated by-a scan after injection of ⁸¹Rb-labelled red cells, damaged with non-radioactive 1-mercuri-2-hydroxypropane (MHP). The clearance time of the damaged cells from the circulation was used as an index of splenic function. The fraction of red cells in the spleen varied from 2.9% to 32% and the splenic red-cell volume ranged from 38 to 1000 ml. In patients with lymphoproliferative disorders their spleens contained a smaller proportion of red cells, relative to splenic size, than patients with myeloproliferative disease. Clearance of cells damaged with 1-mercuri-2-hydroxypropane (MHP) was 30–60 min in normal subjects. Slow clearances were found in some patients with lymphosarcoma; fastest clearances occurred in patients with obvious haemolytic anaemia. No clear relationship was noted between the rate of clearance and splenic size or splenic red-cell volume.     

Regional Variations in the Proportion of Red Cells in the Blood in Man

Surface counting techniques following the intravenous injection of ⁵¹Cr labelled red cells and ¹³¹I labelled human serum albumin have been used to investigate the regional haematocrit in normal subjects, subjects with splenic enlargement and after splenectomy. Regional variations in the proportions of red cells and plasma were demonstrated, the red-cell concentration being highest at the precordium and lowest in the hepatic region. Intermediate values were obtained for the lumbar and splenic regions in normal subjects.
The enlarged spleen has a definite but variable tendency to be associated with high local haematocrit values when compared with the venous haematocrit. Raised whole-body to venous haematocrit ratios result from the pool of red cells in the spleen which shows delayed mixing with the cells of the extrasplenic circulation. The raised whole-body to venous haematocrit ratio associated with splenomegaly is more dependent on the concentration of the pooled cells relative to the venous haematocrit than on the volume of pooled cells and spleen size.
The significance of variations in regional to venous haematocrit and whole-body to venous haematocrit ratios is discussed.     

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.     

Polycythaemia following splenectomy in myelofibrosis with myeloid metaplasia. A reorganization of erythropoiesis

3 patients with myelofibrosis with myeloid metaplasia were splenectomized because of anaemia and disturbing splenomegaly. In the course of the 6 months following splenectomy, a polycythaemia developed. Erythrokinetic studies demonstrated that in all cases a reduction in plasma volume and an increase in red cell volume was obtained. Total erythropoiesis decreased along with normalization of ineffective erythropoiesis and peripheral haemolysis. The reappearance of an erythropoietic activity measured over the sacrum was a constant finding, while in 1 patient, a depression of activity over the liver was observed. The new distribution and organization of erythropoiesis in the splenectomized patients is hypothesized as being due to the removal of the influence of an enlarged spleen on erythropoietic organs.     

Splenic Red Cell Pooling: A Diagnostic Feature in Polycythaemia

S ummary . Total red cell volumes and splenic red cell pools were measured in 31 patients with polycythaemia. 22 had polycythaemia vera (PV), 12 of whom had clinically detectable splenomegaly, and nine patients had secondary polycythaemia (PS). The mean red cell pool was 192.8ml (SD 126.6) in PV (all cases), and 130.9 ml (SD 28.4ml) in PV without splenomegaly; it was 61.1 ml (SD 8.3 ml) in PS. When expressed relative to spleen size (in cm), differences were even more striking: PV (all cases)—mean 13.7 ml/cm (SD 4.3); PV without splenomegaly—mean 12.7 ml/cm (SD 2.2); PS—mean 6.6ml/cm (SD 1.2). Measurement of splenic red cell pool thus appears to be valuable diagnostic tool for distinguishing between PV and PS. The findings point to the presence in PV of a splenic structural abnormality which is not simply an effect of the inceased circulating red cell mass.     

Splenic haematocrit and the splenic plasma pool

A method was established for estimation of plasma volume and splenic plasma pool by quantitative scanning using 113mIn labelled transferrin (TF). The method was used in 12 patients with various haematological disorders and degrees of splenomegaly. 113mIn-TF consistently gave about 6% over-estimation of plasma volume by comparison with the standard 125I HSA method. The splenic plasma pool ranged from 1.2% to 11.4% of the total plasma volume. By concurrent measurement of splenic red cell pool the splenic haematocrit (SHct) was obtained: mean 0.51, SD 0.08; the SHct/PCV ratio was 1.21 (SD 0.31) and the SHct/body Hct ratio was 1.30 (SD 0.30). SHct was independent of PCV and body Hct but there was a trend to a lower SHct in cases where splenomegaly was more marked. Direct measurement of splenic plasma pool may help to elucidate the cause of increased total plasma volume in such patients.     

The splenomegaly of myeloproliferative disorders: effects on blood volume and red blood count

By means of a scintigraphic method for estimation of spleen size, the relationship was studied between spleen size and anaemia, total blood volume and red cell volume in patients with myeloproliferative disorders. There was significant correlation between spleen size and Hb, RBC and PCV in myelofibrosis. The size of the enlarged spleen did not, however, correlate with the degree of anaemia in the leukaemias. There was positive correlation between spleen size and red cell volume in these conditions. It was not possible to evaluate the severity of polycythaemia from spleen size and the degree of enlargement of the spleen does not appear to be a reliable parameter for staging and deciding on treatment in patients with PPP.     

Anaemia in myelofibrosis: its value in prognosis

S ummary . Forty-four patients with myelofibrosis were investigated in our hospital in the period 1971–81. Their clinical, laboratory and radioisotope parameters were analysed. The direct correlation between plasma volume and splenic red cell pool has highlighted the role of the spleen in the dilutional anaemia seen in myelofibrosis. ⁵²Fe quantitation enabled us to show that the bone marrow contributes relatively more to effective erythropoiesis than the extramedullary sites. The prognostic value of changes in plasma volume and bone marrow ⁵²Fe activity has been demonstrated. We have shown that the Hb: reticulocyte relationship at diagnosis can be used to recognize probable stages of the disease and provides a useful prognostic determinant.     

Patterns of Red Cell Destruction in Sickle-Cell Anaemia

Nine patients with sickle-cell anaemia were studied by body surface counting over the spleen and liver following the injection of ⁵¹Cr-labelled red cells. In two of the patients without palpable spleens there was no excess accumulation of radioactivity over the spleen, and the spleen/liver ratio declined with time. In the remaining seven patients, all with splenomegaly, there was decreased red cell survival, an excess accumulation of radioactivity over the spleen, and an increase in the spleen/liver ratio with time, indicative of sequestration of red cells by the spleen. The significance of these findings is discussed.     

Plasma Volume and Splenomegaly in Polycythaemia Vera

Blood volume studies in 23 patients with polycythaemia vera showed the mean plasma volume to be normal when compared with control subjects, and variation in plasma volume for the group as a whole was no greater than in normal subjects. However, the polycythaemic subjects proved to be heterogeneous with respect to plasma volume: in one subgroup, showing splenomegaly with demonstrable intrasplenic red cell pooling, there was a moderate increase in mean plasma volume. In addition, the effect of intrasplenic red cell pooling on the whole body haematocrit/venous haematocrit ratio was found to differ in this condition from the effect in non-polycythaemic subjects: the splenic pool failed to concentrate red cells significantly above the levels present in the extrasplenic circulation, and did not result in a rise in the H_b/H_v ratio.     

Radioisotope studies in monitoring of Gaucher's disease and its treatment

Radioisotope studies (blood volume, spleen function, and ferrokinetics) were performed in seven patients with chronic (type 1) Gaucher's disease. Interestingly, the 52Fe scans and spleen histology demonstrated extramedullary haemopoiesis in the liver and spleen. Radioisotope measurements (red cell volume, plasma volume, red cell pool, damaged cell clearance, spleen blood flow, 59Fe clearance, red cell utilization and 52Fe scans) provide methods for accurate measurement of the bone marrow and spleen function, thereby enabling prediction of the most suitable time for splenectomy, in the treatment of patients with Gaucher's disease.     

The Irreversibly Sickled Cell; a Determinant of Haemolysis in Sickle Cell Anaemia

S ummary . Red cell survival was estimated in a group of adult sickle cell anaemia patients using the ⁵¹Cr technique. Counts of irreversibly sickled cells were performed on thin coverslip preparations of capillary blood. These counts are relatively constant within the same individual but show marked variations between individuals. A significant correlation has been demonstrated between the irreversibly sickled cell count and the red cell survival. This correlation does not apply to sickle cell anaemia patients with splenomegaly in whom the irreversibly sickled cell count is always low.     

Erythrokinetic Studies in Hairy-Cell Leukaemia

Erythrokinetics were studied in 29 patients with hairy-cell leukaemia. In all cases there was an increase in plasma volume, closely correlated to the size of the spleen, indicating that the true degree of anaemia can only be appreciated by red cell volume measurement. Moderately increased haemolysis was observed in most cases, which did not correlate with the spleen size. Simultaneous study of autologous and isologous red cell life-span suggested an extra-corpuscular mechanism for the haemolysis in most patients. A quantitative erythropoietic defect, either relative or absolute, was found in half the cases, without any qualitative defect. Only one case showed erythroid metaplasia of the spleen. Thus marrow failure appears to be largely responsible for the anaemia and granulocytopenia in hairy-cell leukaemia. A clear correlation was shown between the short-term prognosis after splenectomy and the degree of hypersplenism. However, long-term survival correlated chiefly with the degree of bone marrow failure, whether splenectomy had been carried out or not. The results indicate that isotope studies in hairy-cell leukaemia are useful both in determining the best form of treatment and predicting survival.     

Serum cholesterol and triglycerides in children with anaemia

Serum cholesterol and triglyceride levels were determined in 17 children with various forms of anaemia and varying rates of red cell production. Anaemic patients had low serum cholesterol values, and a good correlation between Hb and serum cholesterol levels was found. The serum triglyceride levels were also low in most patients, but the results were less closely related to Hb. No relationship could be demonstrated between the rate of red cell production as judged by reticulocyte counts, and serum cholesterol or triglycerides. Apparently all lipoprotein classes are reduced in individuals with uncomplicated anaemias. This hypolipidaemia can only partly be explained by the diluting effect of the increase in plasma volume accompanying anaemia.     

Red pulp in splenomegaly syndrome: morphometric light and electron microscopy studies

From a series of consecutively studied spleens, perfusion-fixed and investigated according to a standardized procedure allowing morphometric investigations at the light and electron microscopic levels, 33 spleens causing splenomegaly syndrome (12 lymphoproliferative diseases, 10 hairy cell leukaemia, 11 myeloproliferative diseases) were compared with data in controls and autoimmune haemolytic anaemia and hereditary spherocytosis from previous studies. In splenomegaly syndrome, especially in hairy cell leukaemia and myeloproliferative diseases, less so in lymphoproliferative diseases, there is a disproportionate increase in the volume of pulp cords in the red pulp. Values for erythrocyte volume density are of the same order as splenic erythrocyte concentration determined by scintigraphic kinetic methods. Cases with complicating immunohaemolysis show a rather high proportion of erythrocyte profiles with nearly spheric shape as in autoimmune haemolytic anaemia and hereditary spherocytosis.