Are there any risks to colonoscopy prep procedures?

Very few serious ones, though the preparations commonly recommended by doctors can cause nausea, vomiting, painful cramping, dehydration, electrolyte disturbances, kidney damage and even fainting. In very rare instances, a tablet called Visicol has been linked with seizures and a team of Columbia University researchers reported recently on 21 patients who suffered acute kidney failure after colonoscopy preparations.