The anal sac is a small gland located near the anus of many animals, including dogs and cats. These sacs produce a strong-smelling fluid that is used for marking territory and communication with other animals. When an animal defecates, the pressure can help express this fluid, releasing the scent. In some cases, the anal sacs can become impacted or infected, leading to discomfort for the animal. Symptoms may include excessive licking of the area, difficulty sitting, or signs of pain. Regular veterinary check-ups can help ensure the health of the anal sacs and prevent potential issues.