I have been a rat rescuer for eleven years, I recently stopped until I got a call last night about a very sick orphaned brown rat!! I agreed to take him.. upon arrival noticed straight away very underweight, lethargic and has Pneumonia.. he is on 3x medications supplied by vet (baytril half a drop, Theophylline quarter drop and amoxicillin in his formula that is specially made up), I woke up too a more active rat and he has had a good feed! Problem is he hasn't peed since yesterday afternoon (nearly 24 hours), any ideas why?