The usual reason that dogs 'scoot' is due to impacted anal glands. The cause of impacted anal glands is diet. The stool is too soft, due to the grain content or carbohydrate content of the commercial pet food diet. If you were to feed a biologically correct diet of raw meat, this problem should disappear. The stool becomes harder, and smaller, and it expresses the anal sacs more effectively, when the dog eliminates. This anal gland problem can become rather serious, as it can cause infection, and rupture, so a trip to the vet is in order, they know how to express these sacs. Keep in mind, however, that your vet may scare you away from the species-appropriate diet of raw meat, as they have been educated by commercial pet food companies, with regard to nutrition, and these companies have done a very good job of teaching that this kind of diet is 'dangerous'!

If you need any more information about this type of feeding, I would be happy to share my experience.

Good luck.
Gayle