Colonoscopy - why PEG instead of Phospho Saline?

Question

Why is PEG more often used for colonoscopy prep than Phospho? I hear the PEG is the most disgusting witches brew ever concocted and you're supposed to down a gallon of it! Just one container of the phoso cleaned me out to water-in-water-out with just one small bottle. And it wasn't pleasant eaither but at least it was just a glass.

http://www.med.umich.edu/1libr/aha/umpegcolon.htm

http://www.med.umich.edu/1libr/aha/umphosphocolon.htm

Answer 1

For the most part PEG is considered safer. The Phospho soda has an extreme amount of Phosphorus in it. Phosphorus can affect bone resorption and kidney function. Now you don't asbsorb a whole lot, by why risk it. Also PEG is much more effective at evacuating the bowels than is Phospho soda causing a much lower occurance of having to retake the test.

Answer 2

I am not a gastroenterologist so I am only speculating but think about it this way. You have many, many feet of colon, any foot of which could potentially harbor a cancer or precancerous polyp. It does not take much retained stool to hide a potentially lethal lesion. Also, like any surgical procedure, colonoscopy has a tiny, but finite, risk of complications, up to and including death, so you don't want to expose someone to this twice by an incomplete prep. Actually, I personally have downed the gallon of stuff for my own colonoscopy and it is not THAT awful going down.