Izzy had some blood in her poo a few months ago- it was kind of mucousy, streaky and a line too - turned out that it was from straining and she had a little fissure in her bot. As long as it doesn't get worse, I would wait til Monday - but if you think you will stress about it, maybe find an AH clinic? Good luck and I'm sure he will be fine - It's hard not to worry isn't it.