blood on anus

Question
I recently went out of town for two days and had a neighbor feed my mice.When I came home and checked on them one of my smaller male mice had dried feces and blood on his anus.So I washed him with baby soap and put him into his own cage.Few hours later I checked on him and he had blood on his anus,I cleaned the area again and checked for any sores he has none but the area seems to be swollen a little.

Answer
Hi Amy,

It's possible that he was injured, such as a bite from the other mouse, or that something more complicated could be wrong such as an intestinal infection.  The only way to know for sure what the problem is (and therefore how to treat it) would be to take him by a professional vet as soon as possible.  Since you can't directly tell where the blood is coming from this is especially important, as open wounds need to be kept very clean and an intestinal problem could require immediate medication.  Unfortunately, from here, there isn't much else I can tell you to do.

I would check the mouse or mice he was living with, too, for any signs of problems or bite marks that might indicate there was a fight.  Males can suddenly become very territorial and no longer able to share a cage - if his cage mates were male, he will not be able to be placed back in the same cage with them in the future.

Best of luck!