WHAT ARE THEY
Anal sacs are small paired pockets located between the internal and external anal sphincter muscles, one on each side of the anus at the 4 and 8 o’clock position.  The sac empties through a short and narrow duct to the surface near the inside edge of the anus.  Each sac is lined with abundant sebaceous (oil) glands and numerous apocrine (sweat) glands.  The secreted substance is a semi-oily, brownish fluid that packs an odor strong enough to gag a maggot!  For unknown reasons some dogs' anal sacs produce a rather thick, semi-solid material which is much more prone to impacting the sac due to the sac's inability to pass this semi-solid material through the narrow duct to the outside.  In many of these cases the sac will become infected, cause pain and inflammation and even break through to the skin surface.  The abscessed anal sac may need surgery to provide drainage and curettage of the damaged and infected sac and surrounding tissue.  Antibiotics are indicated in abscessed anal sac disease.

WHAT THEY DO
One study indicated that anal sac disorders affects about 12% of dogs. There are a number of theories why dogs, cats, skunks, and other mammals have anal sacs and what possible use they may have.  One theory states that anal sac contents, when excreted with the passing stool or by anal sphincter muscle contraction, act as a powerful territorial scent marker somewhat akin to humans posting a No Trespassing sign.  Another theory states that the anal sac material lubricates hard stool, which makes passage easier.  Humans do not have anal sacs.  It’s bad enough that some humans get hemorrhoids, which are dilated, irritated blood vessels at the anus; luckily, dogs do not get hemorrhoids. 

CAUSES OF ANAL SAC PROBLEMS 
There are no predictable antecedents to painful anal sac disorders.  Infections, obstruction and subsequent overfilling (called impaction), and rupture with drainage through the perianal skin are the most common clinical presentations.  Anal sphincter muscle dysfunction, enlarged anal sacs that are not compressed properly by the anal sphincter muscle, hypersecretion from the anal sac lining, obstructed or constricted anal sac ducts all may be predisposing circumstances for anal sac problems.

IMPACTED ANAL SACS
Some dogs may be born with very narrow channels that lead from the sacs to the edge of the anus, thereby obstruction the flow of anal sac material.  Acquired damage to the duct can occur when perianal infections, trauma, allergies and inflammation compress or obstruct the narrow channel leading from the sac to the surface.  For unknown reasons some dogs produce a thick or dry material from the sac lining which makes passage of the material through the narrow ducts impossible. 

AGE/BREED CONSIDERATIONS
There is no age or sex predisposition to anal sac pathology.  Uncommon in large breeds, infections and impactions are often experienced by small breeds such as Toy and Miniature Poodles, Chihuahuas, and Lhasa Apsos.  Cocker Spaniels, Basset Hounds, and Beagles rank high on the list of breeds affected by anal sac difficulties.

DIET
Some groomers and animal health care workers believe feeding a diet rich in fiber aids in emptying the sacs. The pressure of the firm stool against the colon wall near the anus may help to express the anal sac contents.  Dogs that have an existing problem such as infection or obstructed ducts, though, probably won’t respond to dietary changes; modifying the diet with more or less fiber yields inconsistent benefits.  As a practitioner for over 35 years I have seldom seen a change of diet have any beneficial impact on the frequency of anal sac problems.

GROOMERS
There is a difference of opinion regarding routine expressing of the anal sacs.  For example, veterinarian Mark Thompson in his presentation about anal sacs in Current Veterinary Therapy XIII, suggests routine manual expressing of the anal sacs should not be done in a normal dog with no anal sac issues.  Many groomers make it a matter of routine, though, to express the anal sacs of their dogs.  Certified Master Groomer Sherri Glass, for example, has been grooming dogs for 14 years and has taught grooming for 5 years at Cornerstone Dog Grooming Academy in Clyde, OH.  She relates, “I teach students to empty anal glands on all small dogs, about 20 pounds or less in size.  We also do any size dog at owners request.  If dog owners would meet their dogs nutritional needs with high quality food, keep them at proper weight, and provide plenty of good exercise, most dogs would not have to have the anal sacs expressed.”   Mr. Jeffrey Reynolds, Director of the National Dog Groomers Association of America says “In states were it is legal for groomers to express anal sacs, many groomers express them externally only either as a part of the grooming procedure or at the owners request. When there is evidence that the sacs are impacted, then they are not expressed and the owner is advised to bring the dog to the vet.” 

HOW TO RECOGNIZE A PROBLEM
There is an 88 percent chance the thought of anal sacs will never even occur to you.  However, if your dog is one of the 12 percent that scoots his rear bumper along the carpet, frequently turns to lick or bite at the base of his tail or anal region, or displays discomfort when passing stool, it would be advisable to make an appointment with the veterinarian.  If left untreated, anal sac impactions, infections and abscesses can be a reoccurring nuisance for your dog so be proactive about an evaluation if your dog displays any discomfort in the tail or anal region.

THE ULTIMATE SOLUTION
“Do-it-yourself-anal-sac-expressing” can be done at home once your veterinarian has instructed you.  (Yuck… be careful about contact with anal sac secretions or you’ll be very unpopular with yourself and others!)  Some cases respond to infusion of the sacs with antibiotics in addition to oral medication.  In chronic cases, careful surgical removal of the anal sacs can be curative; the dog never has another annoying bout of anal sac disease.  Be sure to discuss the pros and cons of surgery if chronic problems lead you in that direction. 

	Surgery performed by Dr. Dan Paretsky, Eagle River, WI The patient is a six year old Bassett Hound that had chronic, unresponsive anal sac infections and impactions. The surgical removal of the sacs completely resolved the problems. Click on an image for a close-up view in a new window
The veterinarian points to a swollen anal sac abscess			Infected fluid is shown seeping for each anal sac duct
Dr. Paretsky infuses the left anal sac with paraffin in order to facilitate location and removal of the sac.	Locating and isolating the sac. Careful dissection of the sac is imperative to preserve anal sphincter muscle.	With minimal bleeding and little trauma to the anal sphincter muscle, an excellent outcome is expected.	A view of the resected anal sacs... The patient recovered well and greatly benefited from the anal sac surgery.