The cathiterization went well. The problem was exactly what they thought. The shunt was obstructed, causing her oxygen levels to drop. They put in a stint and her levels went back to normal instantly. Hopefully, this means all is well.
She is still pretty sleepy, but they are starting to give her some Pedialyte. As long as she tolerates that, they will try some formula. If that goes well, she maintains her levels overnight, and there are no other complications, they will send us home tomorrow.