If there is something protruding from the anus, like rectal tissue, or if it is "sticking out", then your dog should be seen right away at an ER hospital, because she might have something called rectal prolapse where the rectum comes out of the anus. If it is just pink and slightly swollen, then you can wait until tomorrow to see your vet. She may be licking at it, which may have caused the irritation, so try to keep her from licking it as much as possible. Also, she may be scooting her rear on the carpet, which could cause this, and that may indicate that he anal sacs need to be expressed.
Hope this helps. Best of luck!
Oh... if it is swollen and red on one side, she might have an anal sac abscess. With the scooting and the one-sided redness and swelling, I can almost guarantee it. This is an infection, and it will eventually rupture. I would get her to the vet tonight or tomorrow and have them cut open the abscess and start her on some antibiotics. It can be very itchy and painful.
Thanks for the extra information that helped me help you! Best of luck.
Dog Veterinarian
Harvard-educated veterinarian with 4 years experience in emergency veterinary medicine.
I just wanted to Thank you for your advice. We took her to the Emergency clinic and it was an anal sac abscess. They are lancing it and she is coming home on anitbiotics.
Thank you again so very much