Protecting your Kidneys during Colon Cancer Screening

Colon cancer screening is very important. It detects cancer at early, more curable stages. But the National Kidney Foundation wants people to know about certain bowel cleansing products that have risks to the kidneys of some individuals. A warning was issued by the FDA for a type of sudden loss of kidney function or acute kidney injury and blood mineral disturbances.

Your colon doctor needs to see your colon without anything in the way. So the bowel needs to be very clean. Many bowel cleaning products are safe. The FDA warning is for bowel cleansing agents called sodium phosphate (OSP) products. These can be used as laxatives as well as in preparation for colonoscopy. OSPs are available both with and without a prescription and are taken by mouth. It is possible that phosphate crystals might be deposited in the kidneys when these products are used by some people. This can cause the loss of kidney function, which can lead to kidney failure. The medical term for this condition is acute phosphate nephropathy".

People with chronic kidney disease are at risk, but other people are also at increased risk. These include people over age 55, people who have bowel obstructions or active colitis, and people who have hypovolemia or decreased intravascular volume (ask your doctor if you have these problems which can be caused by dehydration, bleeding, or the use of certain medicines, as well as other things). Also, some medicines can increase your risk, such as some hypertension drugs, including diuretics, angiotensin converting enzyme inhibitors, or angiotensin receptor blocker drugs. Ask your doctor if you are taking one of these medicines. Some over-the-counter medicines for pain or fever might also lead to increased risk. These are nonsteroidal anti-inflammatory drugs [NSAIDs]), like ibuprofen or naproxen. You can read the label on these pain relievers to see if one of these medicines is in the pill you take.

Oral sodium phosphates clear the bowel by making bowel movements frequent, loose and runny. These agents work by causing fluid loss so patients are recommended to drink large quantities of clear liquids as part of the bowel preparation.

Symptoms of acute phosphate nephropathy are:

• Lethargy
• Drowsiness
• Decreased urine
• Swelling of ankles, feet and legs

Early on, people may not have any symptoms at all. Anyone at high risk for this condition should have their kidney function monitored by their doctor.

Visicol® and OsmoPrep® are available by prescription only. Other similar OSP products are non-prescription, and can be used as a laxative at low doses.

Children under 18 years should not use these products alone or in combination with other laxatives containing sodium phosphate. Others groups who are at risk for acute phosphate nephropathy are:

• People over 55
• People who know they have chronic kidney disease
• People who are dehydrated
• People who have bowel obstruction, delayed bowel emptying, active colitis
• People taking certain medications. Ask your doctor if you are taking diuretics, angiotensin converting enzyme [ACE] inhibitors, angiotensin receptor blockers [ARBs], and inflammation and pain relief medications such as nonsteroidal anti-inflammatory drugs [NSAIDs])

The FDA requested the manufacturer of Visicol® and OsmoPrep®, Salix Pharmaceuticals, to:

• Add a black boxed warning to the pharmacy package insert for these products
• Develop and distribute a medication guide for patients that is easier for most patients to understand than package inserts
• Arrange a post-marketing trial to assess the risks to patients taking OSP products

Non-prescription OSP products have a long history of safety when used as laxatives and are still available over the counter. However, because of the recent warning by the FDA, those OSP products should only be used as laxatives and not for bowel cleansing. The FDA suggests consumers should get a prescription from a health care professional when thinking about having a bowel cleansing.

The U.S. Preventive Services Task Force (USPSTF) strongly recommends that clinicians screen men and women 50 years of age or older for colorectal cancer with one of several tests, including colonoscopy. If your doctor recommends colonoscopy, concerns about bowel cleansing should not prevent you from undergoing colon cancer screening. Colon cancer is treatable when the disease is caught early and the best treatment is to identify and remove precancerous polyps before they progress to cancer. A high quality and safe colon cleansing preparation is important for colon cancer screening with colonoscopy. There are other FDA approved alternatives to OSP for bowel preparation prior to colonoscopy that may be safer for some patients, but may not always clean the bowel adequately. Patients should discuss the risks of the preparation and procedure as well as the benefits of the screening to determine the best bowel cleaning agent for their age and risk conditions as noted above.