Does Lead Overload Develop in Hemodialysis Patients?

Marco Martegani, MD, Divisione di Nefrologia, Ospedale Multizonale di Varese, USSL no 3, v. le Borri 57, I-21100 Varese (Italy) Dear Sir, Lead has been variously associated with gout, hypertension, and renal failure. Thomson et al. [1] described a significant but slight increase in concentrations of red blood cell lead in patients with chronic renal failure (CRF) and on hemodialysis. After EDTA chelation test, Batuman et al. [2] found higher levels of urinary lead in gouty patients with CRF than in gouty patients with normal renal function. The same author measured larger amounts of mobilizable lead in hypertensive patients with reduced renal function than in patients who had hypertension without renal impairment but suggested that this increase could not be due to the renal disease since normotensive CRF patients did not excrete such large amounts [3]. Among CRF patients, Colleoni and D’Amico [4] found a linear correlation between serum creatinine and mobilizable lead only in gouty patients. On the other hand, Behringer et al. [5] and Ritz et al. [6] observed elevated chelatable lead in patients with impaired renal function and lead exposure. Environmental pollution leads to an increasing body lead content in healthy subjects [7], which means that, as lead is mainly removed by urinary excretion [8], a lead overload could occur in patients affected by CRF even without a known or suspected exposure. In a preliminary study, the erythrocyte zinc protopor-phyrin IX (Zn PP IX) level (the increase of which may reflect a lead overload) was determined in 3 groups of patients: healthy subjects, mild to moderate chronic renal failure patients and hemodialysis patients. The results are shown in table I. The differences among the three groups were highly significant; moreover, a linear correlation between serum creatinine and Zn PP IX levels was observed (p < 0.001). Fifteen dialysis patients without lead exposure and high Zn PP IX levels were tested for serum lead. The Table I. Erythrocyte Zn PP IX levels in healthy subjects, CRF and hemodialysis patients determined by direct hematoñuorimetric method (Model 4000; Experimental Sciences Associated) Healthy subjects CRF patients Hemodialysis patients