Anal Sac Disease, Canine

Anal Sac Disease

By Dr. Karen Burgess

What are the anal sacs?
Anal sacs, or anal glands, are two sacs found under the skin near a dog or cat’s rectum.  Located at approximately four and eight o’clock when looking at the anus, these sacs normally contain an often putrid dark colored fluid-like material that exits into the anus via small ducts.  Often considered to be “scent glands”, anal sac fluid is naturally released during defecation or at times of excitement or stress (similar to a skunk).  In the wild, dogs will mark their territory with anal sac material, rubbing their back ends against vertical surfaces to promote expression.

Why do pets develop anal sac disease?
It is unknown why our domesticated pets have anal sac issues.  It may be related to breed, weight, or underlying skin disease (the anal sacs are lined with cells similar to the skin).  Diarrhea or low fiber diets may also contribute to disease.

What are symptoms of anal sac disease?
Pets with anal sac disease often will scoot their bottoms or lick excessively at their anus.  In some pets the material in the anal sacs will become impacted or “plugged”.  The fluid in these cases is often thicker than usual contributing to swelling, blockage, and eventual infection.  With complete blockage, the anal sac can rupture through the skin near the anus leaving a large open wound or matted fur near the anus.  Pets with severe infection may show signs of general illness including lethargy, painful defecation, and anorexia.  If you suspect your pet has an anal sac abscess do not attempt to handle their back end as they may unintentionally bite due to pain.

How is anal sac disease treated?
An isolated episode may only require manual expression of the fluid in the anal sac.  This can be done externally but is more effectively accomplished by a trained professional rectally.  In cases of impaction or abscess, wound care (cleaning, flushing) with sedation is often necessary along with oral antibiotics, anti-inflammatories, and pain medication.  An Elizabethean collar will also be necessary to prevent further self-trauma.  Reevaluation by rectal palpation after infection resolution is necessary to ensure no residual disease or masses are present.

How is anal sac disease prevented?
There is no definitive way to prevent anal sac disease.  Some pets have their anal sacs expressed on a regular basis to prevent issues, but this may also contribute to their inflammation.  Weight control and exercise along with increased fiber intake (idea being that a bulkier stool increases stimulation and thus expression of anal sac material) may help prevent episodes.  In cases of recurrent anal sac disease, diagnostics for food or inhalational allergies (atopy) is recommended.  Surgical removal is an option, but should be avoided at all costs due to likelihood of complications.