THURSDAY, Jan. 23, 2003 (HealthDayNews) -- Exposure to moderate lead levels may worsen chronic kidney disease, but lead-removal treatment can slow the disease's progression and improve kidney function, claims new research.
The study, published in the Jan. 23 issue of The New England Journal of Medicine, focused on 64 patients with chronic renal insufficiency and elevated lead levels in the high end of the normal range. None of the patients had diabetes, the leading cause of kidney failure in the United States.
Of the 64 patients, 32 received chelation therapy -- injections of EDTA (ethylene diamine tetra-acetic acid), a synthetic amino acid, over a 27-month period. The EDTA binds to the molecules of lead in the blood, and the two are expelled from the body in the urine.
Those who received EDTA treatments had "significantly" improved kidney function and reduced lead levels at the end of the treatment period, according to the researchers.
For 32 patients in a control group, who received placebos during the same period, lead levels increased and kidney function continued to deteriorate.
"So if we look at the body lead [levels], we may provide another way to slow the progression of renal disease," says researcher Dr. Kun-Ying Pan, a kidney specialist at Chang Gung Memorial Hospital in Taipei, Taiwan. "And that means a lot because it can reduce the time someone needs to be on dialysis treatment."
The study, he says, demonstrated a direct relationship between elevated lead levels and chronic kidney disease. Anyone suffering from progressively worsening kidney disease of unknown cause should have body lead levels checked, he adds.
Dr. Philip Marsden, a professor of medicine at the University of Toronto and St. Michael's Hospital, says the study shows that those with chronic kidney disease are particularly susceptible to lead exposure. The research also should be a beacon of hope for those with kidney disease and elevated lead levels, adds Marsden, who wrote an editorial accompanying the study.
"Their kidney function was remarkably improved if they got the chelation therapy," Marsden says. "Now we need to be more cognizant of it because if you give them something to treat the high lead levels, it makes them better. It's not academic; it's a practical matter that can save their kidneys."
Dr. David G. Warnock, director of the division of nephrology at the University of Alabama, Birmingham, and president-elect of the National Kidney Foundation, says the findings should lead to more lead screening of patients with chronic kidney disease when the primary cause remains undetermined.
Among those who treat kidney disease, he says, "lead exposure is not necessarily on the first page, and this paper would suggest that since we're always looking for treatable cases of chronic kidney disease, we should bring this forward in terms of the attention."
The Taiwan study went so far as to assert that chelation therapy could improve kidney function enough to delay the need for dialysis by about three years. And, the study says, the tab for chelation therapy would amount to a fraction of the cost of dialysis.
Precisely how or why lead-chelation therapy improves kidney function remains unknown, the researchers acknowledge. But they suggest elevated lead levels may increase reactive oxygen species, highly reactive chemicals that attack other molecules and modify their chemical structure, and that chelation could reduce the level of these chemicals.
Marsden agrees it's unclear why chelation improved kidney function and says the study failed to prove reducing lead levels alone improved kidney function. He says effects of the chelation other than lead reduction could have improved kidney function. For example, he explains, EDTA binds to other compounds, including iron, and inhibits enzymes.
Further research -- with more subjects, including U.S. patients -- could help determine whether significant differences exist between lead exposure levels in Taiwan and North America, Marsden says.
Nearly 8 million Americans, or 4 percent of U.S. adults, have lost more than half of their kidney function, the Johns Hopkins Bloomberg School of Public Health estimates. Another 6 percent, or 11 million adults, have the persistent presence of protein in their urine, one of the first signs that kidney disease is developing.
More information
Learn about kidney disease from the National Kidney Foundation or the American Association of Kidney Patients.
