"Anal sacs" are small sacs located on either side of an animal's anus. They produce a smelly fluid that helps the animal mark its territory or communicate with other animals. Full definition
In some cases, the dog had an episode of diarrhea or digestive upset a week or two before the clinical signs of anal sac disease became evident. (glenerinanimalhospital.com)
Cats affected with anal sac disease may lick the anal area, scoot or drag their bottom along the floor, bite their tails, or have difficulty with defecation or sitting. (petsmagazine.com.sg)
Dogs with anal sac problems can't properly eliminate material that their glands normally produce. (montrealdogblog.com)