Most NHS hospitals offer conscious sedation as an option for gastroscopy and colonoscopy, so you are usually awake, but a it more relaxed and distant from what’s happening. Most places also have Entonox available in addition. Patients almost always say that it’s the bowel preparation done the day before that is the worst bit.
You are right, the gold standard for investigating bowel problems is colonoscopy. CT Colonography, a virtual colonoscopy using CT scanning, is a reasonable second choice. However, we don’t use this for the reasons you stated...if polyps are found and need to be removed, or IBD detected, you still need a colonoscopy to treat, or to diagnose properly.
Your GP is advising you correctly, to thoroughly investigate both of your problems, upper and lower endoscopy are appropriate. There are many bowel problems, but most have similar symptoms, so without a colonoscopy, there isn’t a reliable way to distinguish between colitis, diverticulosis, or bowed cancer. Diagnosed early, the former and the latter are very treatable. If your colonoscopy is clear, they may consider capsule endoscopy. CTC is done in my hospital only if there is a medical reason not to do a colonoscopy, or if the colonoscopy was incomplete, i.e. the terminal ileum was not visualised (the place where the small and large bowel meet). Then it is done for completion, to see the bit of the bowel wall not seen by the scope.
I know how it feels to be terrified of having an investigation, and terrified not to have it. One advantage of endoscopy, is that you get a copy of the reports as soon as it’s over, so you know what the score is. Half of the fear can be worry about what something might be, but I’ve had patients who have been terrified of the actual procedure due to past abuse, and so far, I can only remember a couple who didn’t manage to make it through the procedure.
FIT is good, but if the value is high, you’ll be referred for colonoscopy anyway. And in the meantime, more time is lost. Whether it’s IBD causing your bowel problems or something else, or nothing, getting it sorted is key.
If you feel you might be able to do it, perhaps see your GP for some diazepam to take before you go for your procedure, but let staff know you’ve taken it, as it may affect the amount of sedation they can safely offer you.
I find smears absolutely abhorrent, and take it one smear at a time, so far , so good. Also terrified of dentists! Most people are frightened coming in for any procedure, but I think you’ll find that the staff will do everything they can to help you relax.
Hope you’re okay, OP, I’m keeping my fingers crossed for you, whatever you decide.