Sodium phosphate enemas tied to drop in kidney function

Last Updated: 2016-02-12

By David Douglas

NEW YORK (Reuters Health) - Use of sodium phosphate enemas prior to colonoscopy screening is associated with a decline in estimated glomerular filtration rate (eGFR), according to finding from a large retrospective study.

"Sodium phosphate enemas are associated with a 38% increase in the chance of developing a decline in kidney function one year following the exposure," said Dr. Monica Schaefer of the VA Heartland Network, Kansas City, who worked on the study.

"Our research recommends that the use of sodium phosphate enemas be limited due to the risk of long-term impact on kidney function," she told Reuters Health by email.

In a paper online January 28 in the American Journal of Kidney Diseases, Dr. Schaefer and colleagues note that sodium phosphate enemas are better tolerated and more effective than polyethylene glycol (PEG) preparations. However, they have been tied to kidney injury.

To examine the relationship between their use and eGFR decline, the team studied more than 70,000 Veterans Administration patients. Prior to colonoscopy, they had received sodium phosphate enemas (with or without PEG) or PEG alone. Their average age was 62 years and 95% were men.

The researchers used a 50% increase in serum creatinine level over 15 months to define any eGFR decline, over six weeks for acute decline, and between nine and 15 months to define long-term decline.

Over six months, the incidence rate of any eGFR decline was significantly higher in the sodium phosphate and combination groups than it was in those given PEG alone (4.5% versus 3.4%).

In adjusted analyses, use of sodium phosphate enemas continued to be significantly associated with any eGFR decline (odds ratio, 1.3). This was also true of long-term decline (OR, 1.4), but not acute eGFR decline. Other risk factors included diabetes and non-iron deficient anemia.

One of the study's limitations is that patients with "high serum creatinine levels (low eGFRs) could have been preferentially prescribed PEG over sodium phosphate enemas as a precautionary measure against kidney disease," the researchers caution.

Also, they add, "patients who varied their hydration after the treatment could have modified their kidney injury risk independent of bowel treatment type."

Nevertheless, despite the superior bowel cleansing properties of sodium phosphate treatments, the researchers conclude "the risk of using such agents likely outweighs the benefit."

Co-author Dr. Amina Khan, of the Kansas City VA Medical Center, added in that, "The clinical implications from this study extend beyond avoiding the use of sodium phosphate enemas as part of bowel preparation for colonoscopy."

"We believe the results of our study are applicable to patients who are undergoing other procedures and the prescription of sodium phosphate should be avoided," she told Reuters Health by email.

SOURCE: bit.ly/1PrzmcJ

Am J Kidney Dis 2016.