Popular Colonoscopy Prep Solution May Pose Kidney Risks

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However, patients must refrain from eating solid foods the day before the procedure, while also ingesting a bowel-cleansing liquid to clear out the colon.

The phosphate solution and tablets have been the preparations of preference because of convenience, as they are available without a prescription and require less clear liquid consumption than the polyethylene glycol solution.

To examine risks associated with use of the phosphate products, the authors analyzed kidney function among 268 patients at their clinic who had undergone either a colonoscopy or sigmoidoscopy between 1998 and 2005.

Most were white, with an average age of 68. Two-thirds were women, and none had a history of kidney disease. All the patients followed a standard dietary and phosphate solution prep the day prior to their screening.

Khurana and his team found that its use was associated with a 6 percent drop in kidney function six months later; that figure rose to 8 percent one year later.

"This magnitude of loss of kidney function is significant," said Khurana, who noted that patients undergo numerous colonoscopies over their lifetime, and normal kidney function loss is confined to about 1 percent per year among patients over 40.

Khurana pointed out that the safety risks he observed might ultimately be the result of patients simply not following manufacturer instructions to drink large amounts of clear liquid when consuming the preparation. Undetected chronic kidney disease among older patients undergoing colonoscopies might also play a role in the findings.

Nevertheless, "we believe that PEG preps are a safer option for patients" until further testing is done, he said.

Dr. Hemant K. Roy, an associate professor in the department of medicine at Evanston-Northwestern Healthcare in Illinois, described the findings as "quite alarming" in an accompanying editorial.

However, he stressed that warranted concerns about phosphate solutions should not discourage patients from undergoing colon cancer screening.

"Colonoscopies save lives," he stressed. "We know it works. So this should not dissuade people from doing one. I think we just need to be cautious about the type of preparation we use and who we give it to, so that an extraordinarily rare complication is avoided. And we have options, so there is a way to do that."

More information

For additional information on colonoscopies, visit the American Cancer Society.