Cases of dog constipation can go on for one or two days without serious consequences - if you're not really sure, I don't know that I would take any action just yet. Ruthie once didn't poop for a few days (when I first got her), but was completely fine. A change in diet can cause constipation - have you changed her food recently? Is there a chance that she is eating the evidence? Some dogs eat their own poop and that may be why no one knows if she is going or not. I THINK that when they're constipated they TRY to poop but can't - obviously uncomfortable for them. For constipation, a lot of people recommend canned pumpkin ('pure' canned pumpkin, no seasoning). Pumpkin has lots of fibre and high water content so it's supposed to be good at keeping dogs regular. You could try that if you are really concerned. Opinions on how much to give vary but I would think 1 or 2 tsp a day would be sufficient - someone else on here can correct me if I'm wrong on that.
