I'm sorry, I certainly wish I had some answers for you, but .... I don't. Stool is fairly soft and its pliable. It doesn't really take a "form" until it reaches the end of the colon and the muscles of the rectum and anus are pretty much what decides the "shape" and "thickness" of the stool. It could well be just that you are still a bit "up tight" about
what you've just gone thru w/that intussusception and not really relaxing during a BM. Or if things are moving thru a bit faster than usual and the stool is on the soft side its moving thru w/o bulking up as much as usual. Unless you have known rectal or anal disease involvement I wouldn't worry about
Some people are like Slinkies... Not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs.