Mine had the same thing and the vet said that his anal glads were very enlarged. The groomer normally cleans these out when I take him, but I hadn't had him there in a couple of months. It's really gross to clean them out, so I recommend taking them to the vet or groomers. Mine has done our dogs for 20 years, and it is just something that she does on a daily basis. I also try a little honey to help move them along if they get plugged up.
