I have been asked this question several times over the years. Many people see their dog scooting across the floor and assume that they must have irritation due to worms. However, scooting across the floor is almost NEVER a symptom of intestinal worms. Instead, it is almost ALWAYS an indication that the dogs anal glands are full or impacted.
Every dog has two glands located on each side of the anal sphincter. These glands are filled with a liquid that is sprayed onto the fecal material when the dog eliminates. The pressure of the fecal material passing through the anal opening along with the constriction of the anal muscle help to express the liquid out of the glands. When these glands do not express normally, then they become overly full and the liquid can thicken into a paste like material. The full glands cause an irritation and the dog scoots on his butt to try to express the glands. Occasionally, the dog is successful and the glands empty as a result of the scooting. However, often times, the material inside the glands has become to thickened and they will not empty when the dog scoots. In this case, the glands need to be manually emptied. This is something that you can be taught to do for him. However, due to the unpleasant nature of the task, most people elect to take the dog to a professional (ie vet, vet tech, or groomer) to have them emptied.
There are several factors that contribute to full anal glands. There are some breeds of dogs that are prone to having problems. These are usually small terrier breeds. There are some hereditary issues such as position of the glands that can contribute to the dog not being able to empty the glands naturally. However, most of the time, it is an issue with diet. If the dog is overweight, then the gland are cushioned by fat deposits and are not being expressed when the dog eliminates. Also, the diet can cause the stool to be too soft and therefore, it does not apply enough pressure to express the glands when the dog eliminates.
So, should you worry when you see your dog scooting? Not necessarily. As I stated earlier, often times the dog is able to get the job done by scooting. However, if you see your dog scooting on a regular basis and/or he starts to bite at the area or act as if it is painful, then the glands are probably impacted and you need to have them emptied. Impacted glands can rupture through the dogs skin and cause a pretty nasty infection.