Anal Glands

The anal glands (or anal sacs) are two small pouches located on either side of the anus at approximately the four o’clock and eight o’clock positions. The walls of the sac are lined with a large number of sebaceous (sweat) glands that produce a foul smelling fluid. The fluid is stored in the anal sacs and is released through a small duct or canal that opens just inside the anus. The anal sacs are commonly called ‘anal glands’. The sacs are present in both male and female cats and dogs.

There are several theories for the existence of these glands.

• Dogs often express these glands when frightened. This may have been used by our pet dog’s wild ancestors to scare away predators. These glands are highly developed in the skunk.
• As some of the secretion are expressed when the dog defecates, this is probably why dogs smell each other’s faeces and bottoms.
• Wild dogs use the glands to scent mark vertical surfaces by rubbing their bottoms on them.

In the modern-day domestic dog, they are unnecessary and really serve no useful purpose. The anal sac secretion contains chemicals that act as territorial markers or ‘dog calling cards’. The secretions are similar to those produced by a skunk, which are used to repel enemies and alert other animals to their presence. Anal sac fluid is usually squeezed out by muscular contractions whenever the dog passes a bowel movement, providing a distinctive odour (or individual ‘scent signature’) to the faeces. This is why dogs are so interested in smelling one another’s faeces.

There are three progressive stages of anal sac disease. These stages include anal sac impaction, anal sacculitis, and anal sac abscess.

• Anal sac impaction occurs when the liquid accumulates and thickens, causing the anal glands to become distended and difficult to empty. This can usually be relieved by expressing the glands manually.
• Anal sacculitis is inflammation of the anal sac. In this stage, the anal sac material continues to accumulate and may become infected by bacteria.
• The final stage is the formation of an abscess. This is the most severe and painful stage and generally requires surgical intervention. Sometimes the abscess can rupture through the skin, leaving a hole that is visible next to the anus. Under sedation or anaesthesia the anal gland is cleaned and flushed.

The reasons for the gland not expressing can include:

• A recent bout of diarrhoea or soft faeces which causes less pressure on the glands when the dog defecates.
• Overweight dogs are more susceptible as excess fat around the ducts can cause them to block.
• Some dogs are simply born with very small ducts, which do not allow the glands to express easily. This particularly applies to small breeds.

As the secretion builds up in the gland it causes irritation and eventually pain. The dog will scoot their bottom along the ground to try and relieve this. Scooting can also be caused by tapeworm infestation, skin problems or allergies, but anal gland impaction or infection is by far the most common reason. A drop of foul smelling material may be left where the dog has scooted. Dogs will often lick around their anus or thighs and sometimes bite at their tail. As defecating can become painful, dogs may cry out or yelp while trying to pass a motion. If an infection or abscess is present pus or blood may be seen. Some dogs have glands that drain continuously due to very open ducts, which can lead to frequent drops of anal gland secretion on furniture or around the house.

Diet

Increasing the amount of fibre in the diet can assist with the anal glands emptying by increasing the bulk of the faeces, which then puts greater pressure on the glands when a motion is passed. This can be achieved by adding bran or psillium husk into the food. However, this does not work in a majority of dogs as the duct openings are often just too small to drain properly.

Weight loss

Overweight dogs tend to present more often for anal gland problems and sometimes the problem resolves by simply losing some weight.

Expressing anal glands

Impaction of the anal glands can be treated by manual expression of the glands by your veterinarian (who can also teach you how to do this if you are interested!). Dogs vary in their production of anal gland secretion, so some effected dogs only need this done every few months, particularly if the glands occasionally express on their own, whereas other dog’s glands may fill up in just a week or two.

Anal gland infection/abscess

A prolonged course of antibiotics is needed. Often a swab is taken to determine the right type of antibiotic. Some dogs require sedation to flush the anal gland and pack it with antibiotic ointment.

Anal gland removal

If anal glands continually refill within a short space of time, and your pet is in continual discomfort from anal gland disease, the anal glands can be surgically removed. This procedure can result in complications, and is only recommended for severe cases of anal gland disease. The tissue around the anal glands is very delicate. If the anal sphincter muscle is damaged in the operation, faecal incontinence may result. This usually resolves after one to two weeks, but very rarely can be permanent. If part of the gland is not completely removed, the secretion can build up under the skin without any means of drainage, resulting in an abscess, requiring a repeat surgery to remove more tissue. Barring these possible complications, surgical removal does result in complete resolution of anal gland problems.