Every dog and cat has 2 anal sacs located on each side of the anus just underneath the skin. These are sometimes called "scent glands". The anal sacs open to the outside by tiny passageways or ducts. Glands within the anal sacs produce a characteristic foul-smelling fluid that is normally emptied by pressure each time your pet has a bowel movement.

The most common reason for "scooting" is a problem with the anal sacs. These problems include impaction, infection, abscessation and rupture, and tumors. Normally anal gland fluid is watery and brown in color and is easily expressed. Impaction of the anal sacs occurs when the fluid becomes abnormally thick and cannot escape naturally through the tiny ducts, resulting in pressure and discomfort. Infection produces a green, yellow, or bloody pus instead of normal anal sac fluid. Abscessation is a result of infection, and a hot tender swelling near the anus may rupture and discharge pus and blood.

Treatment of anal sac impaction may be simple manual expression (squeezing) of the sac contents. In the case of infection, treatments may include flushing the sacs and instilling antibiotics, surgical drainage, or oral antibiotics and pain medication as needed. In severe or recurrent cases the anal glands can be removed surgically.

While anal gland problems are the most common reasons for scooting, there are other less common reasons such as skin infections, allergies, feces adhered to the hair around the anus, and rarely intestinal parasites.