Dog Anal Gland Infection

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A female vet examines a dog in an exam room.
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Characterized by swollen, red swelling on either side of a dog's anus, anal gland infection is caused by bacteria that enters the gland, most likely through the duct. Affected dogs may bite or lick the area beneath their tail, or scoot their bottoms on the ground to alleviate discomfort. Untreated infections may cause the anal sacs to burst, causing damage to the dog's anus and rectum.


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Healthy Anal Sac Function

Present in all predatoray animals, anal glands are two small pockets located below and to either side of the anus. The sacs are lined with sebaceous glands and apocrine, or sweat, glands that produce an oily brown fluid. The fluid empties through a short, slender duct near the inside edge of the anus. When the dog passes stool, pressure on the anal sacs causes them to release their pungent liquid onto the surface of the stool, which facilitates dogs' marking of territory and identification of other dogs by their glands' unique scents.


Causes and Risk Factors

Certain factors may create circumstances that encourage the infection of a dog's anal glands. Small breeds of dogs, such as the Chihuahua and toy and miniature poodles are particularly susceptible, according to Pet MD. Although the causes of infection may be unknown, dogs producing chronically soft feces or recovering from bouts of diarrhea may be prone to anal sac infection. Certain dogs may produce higher amounts of glandular secretions, resulting in impactions; others may have poor anal muscle tone and are thus unable to excrete the excess fluid. Anal sac infection may occur more frequently in a dog diagnosed and treated for anal sac carcinoma.


Dietary Factors

Many dogs are sensitive to the processed grains present in commercial pet food, and anal gland infections may be a result of this sensitivity. According to Dr. Karen Becker, a Chicago veterinarian with a website sponsored by Mercola, foods that contain corn, potatoes, soy, wheat, oatmeal and rice can trigger in canines an autoimmune response that results in the buildup of fluid in the dog's anal sacs. Dogs may experience similar symptoms due to the consistent consumption of only one or two types of protein. Becker suggests feeding a species-appropriate diet along with probiotics and digestive enzymes to ease digestion and avoid infections. Dogs with chronically soft stools may benefit from a fiber supplement, such as bran, to add bulk.


Diagnosis and Treatment

If the dog's anal glands are infected, the veterinarian will perform a physical exam and may inquire about the dog's history, when symptoms appeared, and what may have occurred to aggravate the condition. A blood chemical profile, electrolyte panel, urinalysis and complete blood count may be performed to rule out other causes. The vet may take a sample of fluid from the infected sac for testing and culture, and will express the sacs if they have not ruptured. Once drained, the sacs can be cleaned and flushed, then treated with antibiotics. If the dog's conformation prevents the anal sacs from emptying naturally, surgical correction may be required to prevent future infections.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.