Colonoscopy
I have had several Colonoscopys and never had a problem with any leakage. For me the worst part of the procedure is drinking the prep prior to the procedure. During the procedure you will more than likely be somewhat sedated, and afterwards following a short period of recovery you will be released and go about your day pretty much as normal. You should get your results back within about three weeks.
When I had a series of colonoscopies I was able to watch the screen and had a running commentary from the medical staff, effectively giving me and instant report on the result.
In answer to the question about subsequent leakage the effect is no different from passing a large turd.
I am an OR nurse (retired now) and the only issue is that depending on if they do a biopsy you could have a small amount of post-operative bleeding. Additionally, lube is used to insert the scope and while you will clean up before getting dressed to leave residual may present itself when you use your abdominal mussels lastly depending if the passage is narrow air is used to dilate to allow the scope to reach the colon. In that case, passing gas is very normal and with the prep could lead to wet ones. I would advise an undergarment until you get home and then sit on a towel for the rest of the day while you recover.
Leakage, where? The colonoscopy is a painless procedure. I have had a few colonoscopy in my life. Sometimes I get to watch on a monitor. One time I ate a lot of green jello before the procedure and it looked like the scop was going down a green tinted tunnel. Do not worry the clean up real good with no leaks.