If your dog starts scooting his butt across the floor, that's a sign of anal gland impaction. (dogcare.dailypuppy.com)
Dogs scoot for lots of reasons, from anal gland impaction / infection to lower GI tract parasites like tapeworms to even constipation from many causes, allergies, etc.. (blog.petmeds.com)
In dogs, impactions can be relieved by expressing the anal glands, but in my experience, cat anal gland impactions are much less likely to be detected until an abscess is detected. (blog.nhvnaturalpetproducts.com)