If it's a male cat it's usually a sign of rape from another male.
If the bleeding is heavy you'd have to take it to the vet as it could be a sign of amongst other minor ailments, the more serious bowel cancer. x
Your cat may have something wrong internally. Bring it to the vet to be looked over. Ps. If your cat is female, and is not 'fixed' then you have nothing to worry about most likely, especially if this...
I am not a vet. You need to schedule an appointment with your vet asap. The most common problem, in my experience, is parasitic intestinal worms. Don't fret, your vet will provide you with de-worming...
more than likely something is lodged in the intestine. you will probaly have to take him to the vet. my dog did the smae thing and it almost killed her.
It could also be colitis. my vet fixed my rat...