It could be that he had the blockage and is now making a slow recovery. If you're offering him food then offer things like boiled fish/chicken with rice.
My boy, now sadly passed due to a RTA, came home once looking very bad, just started fading like he had given up on life, normally a big eater he wouldn't eat or drink anything, wouldn't get up. I was about to take him to the vet when my mum, a nurse, came round and gave him some water via a syringe into his mouth before I could stop her (I was worried about him choking. He perked up later that day. I think his might have just been a tummy bug from raiding someone's bin though.
It was horrible seeing him fade and not knowing what to do though, think it was only 24 hours with him but still awful. That your boy is drinking and weeing is a good sign, dehydration can be really bad for them.
What's his name? I'll keep him in my thoughts.
Dans