John, there is a blood test now, and Cologuard, as second-best options to a colonscopy, but colonoscopies are the gold standard. I don't know what a failed colonoscopy means. Not optimal or not able to complete? There is a big difference.

As far as stopping them, you have to consider your health history, your diet and lifestyle, and your MD's view.

Colonoscopies are assembly-line. They schedule you for 20 mins or so and may not like to take longer if you don't fully clean out. How do I know? I have had a shaming experience too. Maybe get a second opinion?

P.S. There has to be someone at Cleveland Clinic for you. They specialize in gut issues.

As jen1926 suggested, starting days before the scheduled colonoscopy is the only way it works for me. Low residue foods and lots of water for 2-3 days and then 2 full days of prep. Day 2 is the exact same prep as day 1, however your Dr. instructs your prep. I take Miralax every day regardless of colonoscopy prep due to chronic constipation and methane archaea overgrowth following a colon resection many years ago. If Miralax is part of your prep regimen, you might consider taking it during the pre-prep extra days to get things going, as it were. I am in the Cleveland area and see a gastroenterologist at the Cleveland Clinic, though I honestly think it’s less about the Dr. and more about the preparation. If I’m accurate in that regard, it’s more in our control, and that gives me hope that I can get a good exam with a prep approach tailored to what my loopy colon needs. I wish you the best of luck, the extended prep isn’t a picnic but beats having to wonder about accuracy of the results.