I agree with Midwest, perhaps theres a more tolerable prep. I drank a fizzy soda prep that was lemon-lime flavored. It was much better than the gallon jug that you mix with water and have to drink the whole thing. But the prep is no fun, it made me dizzy and feel nauseous- Plus fasting only clear liquids for 2 days. ugh
If your husband does IViG or dexamethasone before the colonoscopy, I would think there is no need to worry about bleeding. His counts should be up to a safe level. My platelets were 50K for my colonoscopy (I get Nplate injections), the gastro doc removed a polyp then cauterized the wound. There was no bleeding at all with prep, procedure or post op. Everyone is different, but if your husband lives with a count of 20, I would say not to worry since his count will be higher after IViG.
I have heard that the FIT test (poo test) is 73% accurate if done every year. But it only catches cancer and bleeding. Where as a colonoscopy catches pre-cancer before any bleeding. I have not heard of anything else to replace colonoscopy. I would imagine that a scan would not be helpful because if they found anything, they would have to then go in with a colonoscopy anyway for a biopsy.