Vardaman Buckalew, M.D., a nephrologist at Wake Forest University Baptist Medical Center and a coauthor, said that heavy use of aspirin or acetaminophen is associated with a recently discovered condition known as SICK (Small, Indented and Calcified Kidneys). SICK is detected by CT scan of the kidneys of people with irreversible kidney failure.
"We conclude that heavy use of analgesics at least nine years prior to the development of ESRD [irreversible kidney failure] is associated with the anatomic changes of SICK," reported the eight-member research team of the National Analgesic Nephropathy Study.
Of those patients with SICK, 33 percent had overused analgesics preceding the start of dialysis, Buckalew said. "We're not sure why the other people got SICK."
Overall, 7 percent of the 222 dialysis patients in the National Analgesic Nephropathy Study were found to have SICK.
The study tested whether CT scans could be used as a diagnostic tool to find patients who overused analgesics. The CT scans missed 14 heavy users, and falsely identified 10 patients as heavy users who did not use analgesics heavily.
The research team concluded, "The CT scan is not a sensitive test for the identification of heavy analgesic use among [irreversible kidney failure] patients in the American population."
Buckalew said, however, "If a patient does have SICK, there is an increased likelihood of analgesic abuse."
Buckalew said that may indicate that some people are more susceptible to developing
SICK from heavy analgesic use -- defined as .3 of a kilogram (300 grams) per year. That works out to be about two doses of full-strength aspirin or extra strength acetaminophen every day for a year. (He stressed that it does not include those patients taking a dose of baby aspirin for prevention of heart attack or stroke.)
"We think just some individuals are susceptible," he said. "But there is no way yet to figure out which individuals are susceptible and which aren't."
The study, which also included the University of North Carolina School of Medicine in Chapel Hill, the University of Texas Southwestern Medical Center in Dallas and the Medical College of Ohio in Toledo, studied 222 patients who already were being treated for end-stage kidney disease, of which 52 - the largest group - were at Wake Forest. But none of these patients had diabetes or any other of the usual causes of kidney failure.
Trained personnel also questioned each patient in the study about whether they used analgesics heavily.
William L. Henrich, M.D., professor of medicine at the University of Maryland School of Medicine in Baltimore, presented the findings today.
Wake Forest University Baptist Medical Center is an academic health center including Wake Forest University School of Medicine and N.C. Baptist Hospital.