ALTHOUGH it is clear that the erythrocytosis often found in patients with renal cysts is caused by excess production of an erythropoietic factor, it is not known whether this factor is actually produced by such cysts or released from some other tissue under stimuli related to these lesions. This report describes a patient in whom erythrocytosis remitted following surgical drainage of a solitary simple renal cyst. The renal cyst fluid, as well as samples of plasma and urine obtained before and after renal cyst decompression, was assayed for erythropoietic activity. Tissue culture media, in which a portion of the renal cyst wall had been incubated, were also assayed. Our study suggests that renal cysts associated with erythrocytosis stimulate release of an erythropoietic factor from the kidney but do not directly produce such a factor.
Report of a Case
In November 1965, a 46-year-old white man an active-duty army sergeant major,