it's an interesting question. if an object of any size or shape gets inserted into the rectum it can get stuck (or as we like to say in medicine "retained") due to the strength of the external anal sphincter. this is the powerful muscle that enables us to hold in or release stool. when an object slips beyond the anal sphincter it can be very hard to get out. you might be surprised how many people go to the emergency room each year to have a foreign object removed from the rectum. however it's unlikely an object would travel up the bowel and deeper into the colon. in the first place peristalsis (a rhythmic contraction of muscles along the digestive tract) naturally propels the contents of the intestines toward the anus. for a foreign object to move against the effects of peristalsis would be akin to a salmon swimming upstream. that's not to say it absolutely couldn't happen i guess. never say never? wishing you well!
can a round object travel up from your rectum into your colon and get stuck?