The anal sacs are a pair of marble-sized glands in dogs and cats found beneath the skin around the anus at about the 4 o’clock and 8 o’clock positions. These scent glands (similar to those of skunks) normally squeeze out a small amount of bad-smelling fluid onto the feces during a bowel movement. Sometimes, when dogs get excited, the anal sacs will discharge some of their characteristic foul-smelling contents. When the sacs become infected or the opening through the skin becomes plugged, the anal area can become irritated, inflamed, itchy, and painful.

The most common sign of an anal sac problem is “scooting,” or rubbing the butt along the ground or floor, which can leave behind a small, smelly stain. Dogs often also lick, chew, or bite at the anal area to try to relieve the itch and irritation. Swollen, infected sacs can eventually rupture, oozing bloody pus through a hole underneath and to one side of the anus.

Your veterinarian will insert a gloved finger into the anus to determine if the anal sacs are enlarged. He or she will often be able to express the sacs by applying gentle pressure to “milk” the contents through the normal opening in the skin. The anal sacs need to be expressed regularly in many dogs to prevent the contents from becoming impacted, leading to infection. In some cases, a small tube may need to be inserted into the opening in the skin to remove any obstruction and flush out thickened material. In cases of severe or repeated obstructions, your vet may recommend surgery to remove the glands. Surgery provides a permanent solution but is associated with a slight risk of fecal incontinence from injury to the nerves or muscles around the anus.

If you're interested in learning how to express anal glands yourself, you should discuss the proper technique and potential complications with your veterinarian first.

Q&A

What are anal sacs?
The anal sacs are a pair of marble-sized scent glands found beneath the skin around the anus at about the 4 o’clock and 8 o’clock positions.  

Can anal sacs cause a problem?
The sacs can become infected or the opening through the skin can become plugged, leading to an irritated, inflamed, itchy, and painful anal area.  

How do you treat problems with the anal sacs?
Your veterinarian will insert a gloved finger into the anus and apply gentle pressure to “milk” the contents through the normal opening.  In cases of severe or repeated obstructions, your vet may recommend surgery to remove the glands.  

Written and reviewed by John A. Bukowski, DVM, MPH, PhD
and Susan E. Aiello, DVM, ELS