SPLEEN SIZE IN POLYCYTHEMIA

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Abstract
The size of the spleen has been determined in control subjects, in patients with polycythemia vera (PV) and in other forms of polycythemia. With 99mTc sulphur colloid and a gamma camera technique the largest area of the spleen was determined and compared with the length of the spleen on X‐ray examination and with results of palpation. The spleen scan area was shown to be enlarged in all but three cases of untreated PV (90%) and in all cases of PV in relapse. The group of absolute polycythemia other than PV had a slight but statistically significant increase of the scan area compared with the controls. The group of pseudopolycythemia had a scan area within the normal limits. In cases of active PV the size of the spleen was examined twice, at a high hematocrit level and at a normal hematocrit level, accomplished by repeated phlebotomies. The results did not show any statistically significant difference. There was, however, a significant decrease in the size of the spleen after remission, induced by myelosuppressive therapy. Most normal‐sized spleens were also judged as normal on X‐ray examination, but within the normal range there was no correlation between the spleen scan area and the length of the spleen on X‐ray. A fairly good correlation was found for enlarged spleens, but the residual standard deviation was rather large. Thirteen scintigraphically enlarged spleens had a normal X‐ray length. Twenty‐three enlarged spleens and the normal‐sized spleens could not be felt by palpation. A largest spleen scan area of above 81 cm2 is regarded as above the upper limit of normal. A value above 104 cm2 is in favour of PV, when this disease is to be differentiated from secondary polycythemia.