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.