Postrenal transplant erythrocytosis: further evidence implicating erythropoietin production by the native kidneys.

True erythrocytosis is a relatively common complication of successful renal transplantation. From a group of 17 patients with post-transplant erythrocytosis (PTE), four underwent selective venous catheterization of the native and transplanted kidneys because of arterial hypertension. In three who presented with active PTE at the time the procedure was performed the peripheral blood (PB) concentration of EPO was elevated, and the level of erythropoietin (EPO) in native kidney veins was significantly higher than the PB and allograft EPO levels. Additionally, only one of the three cases had high levels of plasma renin activity (PRA). The fourth patient showed normal levels of EPO and PRA in PB and in venous blood from the native and transplanted kidneys. However, the PTE had subsided 4 months before the performance of the catheterization after he redeveloped terminal renal failure; the loss of a functioning allograft might have blunted the overproduction of EPO by the native kidneys. In conclusion, in patients with PTE, inappropriate EPO production seems to originate from the diseased native kidneys, and there seems to be no correlation between the production of EPO and the PRA.