Following the reports of kidney damage in people who had used some sodium-based bowel cleansing products before colonoscopies, the U.S. Food and Drug Administration said it would require the warnings on Salix Pharmaceuticals Ltd’s Visicol and OsmoPrep prescription products to caution about acute phosphate nephropaty, a type of acute kidney injury.

The agency said it received more than 20 reports of a serious form of kidney failure among patients taking the bowel-cleansing drugs, known as oral phosphate products. Three of those cases were confirmed by biopsy. The injury may lead to permanent kidney damage, the agency said. Agency’s regulators said that in some cases, the injuries occurred in patients with no pre-existing health factors that would have put them at risk of developing permanent kidney damage.

The FDA is “equally concerned” about the risks associated with the nonprescription oral sodium phosphate products when they are used at higher doses for bowel cleansing, according to its statement. Drinking plenty of fluids can help prevent the injuries, according to the FDA.

The agency, however, admitted that some of those patients might have been dehydrated prior to ingesting of OSP products, or might not have followed directions outlined on the drugs, which instruct patients to drink up to half a gallon of water with the tablets.

The FDA recommends that people use caution with those products if they are in the following risk groups: people older than 50; people suffering from dehydration, kidney disease, acute colitis, or delayed bowel emptying; people taking medications that influence kidney function, such as diuretics, ACE inhibitors, angiotensin receptor blockers, and possibly nonsteroidal anti-inflammatory drugs.

The agency advised consumers not to use over-the-counter bowel cleansers, though all the problems reported to the FDA were related to the use of prescription products.

Regular colonoscopies are recommended for all people over the age of 50 and for those who have some pre-existing conditions that put them at risk of developing colon cancer. Studies have shown that regular screening for colorectal cancers could reduce deaths from the disease by catching it in the earliest stages, when the disease is often asymptomatic.

Doctors say the cancer has a 90 percent cure rate when caught in the earliest stages, but people avoid the standard procedure because it is unpleasant. The traditional colonoscopy method involves inserting a long and flexible tube in a patient’s large intestine (rectum and colon). A cleansing of the bowels is needed before the procedure. A small video camera is attached to the colonoscope so that your doctor can take pictures or video of the large colon. The test helps find ulcers, polyps, tumors and areas of inflammation or bleeding.

Colon cancer, also called colorectal cancer, is the second leading cause of cancer death in the United States and the third most common one in the Western world. The disease includes cancerous growths in the colon, rectum and appendix. Statistics show the disease causes 655,000 deaths worldwide per year.