Dear Dr. B: I have been booked for a colonoscopy. I know I have to have my bowel cleaned out for this test to be successful. I am worried about using Fleet Phospho-soda (oral sodium phosphate product) bowel cleansing laxative because of the recent negative media reports. What should I do, doctor?
Answer: US Food and Drug Administration (FDA) issued an alert in December, 2008 which said, “FDA has become aware of reports of acute phosphate nephropathy, a type of acute kidney injury, associated with the use of oral sodium phosphate products (OSP) for bowel cleansing prior to colonoscopy or other procedures.”
FDA also says that in some cases when OSP is used for bowel cleansing, kidney failure has occurred in patients without identifiable factors that would put them at risk for developing acute kidney injury.
FDA recommends, in light of the risk of acute phosphate kidney injury, over-the-counter laxative OSPs should not be used for bowel cleansing. Consumers should only use OSPs for bowel cleansing pursuant to a prescription from a healthcare professional.
Fleet Phospho-soda has been used for many years, on millions of people, in many countries. It has been popular because of low cost and small volume of fluid to drink. The incidence of side effects is minimal in healthy individuals. There are three dangers associated with OSP in venerable patients who have heart failure or kidney disease – dehydration, electrolyte imbalance and phosphate injury to kidneys.
OSP is popular amongst physicians because it has been found to be a better bowel cleansing preparation than many other similar products.
FDA’s warning regarding kidney injury with OSP is of real concern to physicians and patients. A study published in the American Journal of Gastroenterology (103(11):2707-16, 2008 Nov.) concluded that in patients with preexisting kidney disease, OSP use was associated with an increased risk of kidney dysfunction. Their suggestion was to measure the kidney function before OSP administration in order to avoid its use in patients with renal disease.
Is bowel preparation before colonoscopy a risky business for the kidneys? This is the title of an article in Nature Clinical Practice Nephrology (4(11):606-14, 2008 Nov.). It says that in 2004, five cases of irreversible renal failure after bowel preparation with OSP were reported.
The authors say that more recently, several retrospective studies have shown that the incidence of acute kidney injury after OSP use is in the range of one to four per cent, similar to the incidence of contrast kidney disease in patients who undergo special x-rays where contrast dye is used.
During bowel preparation physicians should watch for and correct any fluid and electrolyte imbalance. Patients should be checked for kidney function and serum phosphorus level after colonoscopy. Other option would be to use alternative bowel cleansing agents.
What should you do if you are going for a colonoscopy? If your doctor wants you to use Fleet Phospho-soda to cleanse your bowel then your kidney function should be normal and you should have no cardiac problems like heart failure. The risk of kidney damage in healthy individuals is about one to four per cent. There are other bowel cleansing agents in the market. You can discuss with your physician what are your best options for a good clean out.
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