From the Life's Abundance May 2014 Newsletter:
If you’ve ever noticed a foul odor wafting from your pet’s hind end, there's a chance that anal sacs may be the source of the problem. As any pet parent will tell you, nothing smells as uniquely terrible as the material emitted from these glands. In some mammals, including dogs and cats, anal sacs are small pouches which store secretions from the glands between the internal and external sphincter muscles. A dog or cat can discharge the material collected in the sac through these ducts.Dr. Jane Bicks
One thing this liquid has in common: it almost always has a terribly offensive odor, and one that is difficult to remove from carpets, beds and clothing. The function of these small but potent scent glands is believed to be for territorial marking and communication. Those unfortunate enough to have unexpectedly frightened a dog may have experienced the canine’s ability to ‘spray’ their glandular contents - sometimes as far as six feet! Some biologists believe, for the ancestors of modern day dogs and cats, these organs were not only used in communication, but could also have been used as defense (much as a skunk sprays for self-preservation).
I can assure you that when the trapped substances are released, they’re sufficiently foul to ward off any human predators! In most animals, anal glands function completely normally. For the most part, if it’s not a problem, you’d never have a reason to know about them. Many pet parents don’t even know that their pet has anal glands. However, for some dogs and cats, anal glands can be a real pain in the tukkis. With long-term inflammation, the sacs can become impacted and infected. In severe cases, they can actually rupture. The first sign of trouble is when your dog or cat hunches up and scoots his butt across the floor. That, or repetitively and excessively licks his hind end. If you notice either of these signs, a trip to the vet’s office is warranted. If the problem recurs, pet parents can feel helpless in warding off this noxious – not to mention, painful - problem. Adding fiber to the diet (such as a tablespoon of sweet potato with meals) can provide some relief. Some pet kids (dogs more often than cats) will need to have their glands emptied on a regular basis.
While some groomers offer this service, veterinarians and vet technicians are trained in techniques to completely drain the glands. Which is to say, if your pet is predisposed to this sort of problem, I recommend that a medical professional do the procedure (referred to as ‘expressing’). If the area becomes infected or impacted, understand that the condition is very painful, and should be addressed as soon as possible. They may require pain medication, and perhaps even a course of antibiotics. For some pets with chronic cases, vets may advocate surgically removing the glands entirely.
If you’re looking for a culprit, know that this is just an unfortunate consequence of genetics. While not unheard of, this medical issue is less of a problem for large and giant breeds. Even if your dog isn’t one of the small-to-medium size dogs predisposed to the difficulty, should you notice any signs of discomfort, don’t rule out anal sac problems. Thank you for all you do to make the world a better place for companion animals.