Bowel Preps Can Cause Renal Damage
Pre-hydration may decrease the risk associated with the use of oral sodium phosphate solution.
SAN FRANCISCO—The use of phosphate-containing solutions to prepare the bowel for colonoscopy or surgery may cause significant damage to the kidneys, according to a researcher who spoke at a special clinical update here during Renal Week 2007.
Glen Markowitz, MD, of
In 2006, the FDA issued an alert about this complication, including advice to avoid oral sodium phosphate solution in patients with kidney disease. Dr. Markowitz said that the FDA warning, together with careful selection of the most appropriate “bowel prep” for individual patients, may reduce the number of patients with this condition.
Five cases of acute phosphate nephropathy at five different centers were reported recently, and all involved women (age 56-85 years). None of the women returned to baseline renal function after the condition developed (Nephrol Dial Transplant. 2006;22:920-922). Dr. Markowitz said that it may be possible to prevent additional cases of acute phosphate nephropathy in the future by better identifying risk factors.
For now, it appears that possible risk factors include female gender, small body habitus, and use of nonsteroidal anti-inflammatory drugs. Probable risk factors include inadequate hydration, advanced age, hypertension, treatment with angiotensin receptor blockade or diuretics, excess phosphate dosing, and a short interval between the two doses of OSPS, Dr. Markowitz said.
“This is a very important tissue,” said Dr. Markowitz, associate professor of clinical pathology and the associate director of renal pathology laboratory at
To determine the frequency of acute kidney injury (AKI) with OSPS use, researchers at
The researchers, who reported their findings at the meeting, looked at a total of 16,826 patients who had a colonoscopy during this study period. Of these, 9,799 subjects (58%) had available serum creatinine values within 365 days before and after the procedure date. The investigators identified AKI in 114 patients (1.16%). After adjusting for significant covariates (age, diabetes mellitus, hypertension, and diuretic use) and other suspected risk factors for AKI (such as IV contrast exposure), use of OSPS was associated with a greater than twofold greater risk of AKI than an alternative agent, polyethylene glycol. In addition, older age was independently associated with AKI, the researchers reported.
“I do think we can reduce the risk,” Dr. Markowitz told Renal & Urology News. “If you drink a lot and don't get dehydrated while you are doing a bowel prep, your risk is lower. The pharmaceutical companies have appropriately raised their requirements for hydration.” Another strategy is to reduce the phosphate content of the OSPS, he said, adding that companies are now making solutions with less phosphate in them.
Also at the clinical update, Daniel Coyne, MD, of Washington University School of Medicine in
Despite the risks, he told colleagues, bisphosphonates remain very important in treating the high rate of osteoporosis in patients with kidney disease. Recent studies have even suggested that bisphosphonates can slow buildup of calcium deposits in the blood vessels of patients on dialysis.