Don’t worry – anal gland problems are very common! In this blog, we’re going to look at your dog’s anal glands – how they’re supposed to work, what sort of things go wrong, and how to fix them again.


What are anal glands?

Strictly speaking, they should probably be called anal sacs; they are a pair of hollow sacs just inside the dog’s bottom. If you look at your dog from behind, they sit at roughly 4 o’clock and 8 o’clock, one on each side. You won’t see the draining ducts though – they open inside the rectum. Within each sac are lots of tiny microscopic glands that secrete a vile-smelling fluid.


What are they for?

Essentially, dogs use them for scent marking. Dogs like to recognise who else is around by scent, so they need some way of making their faeces smell unique. However, as dogs in the wild generally have a pretty similar diet, this individuality maintained by producing slightly different smells in the anal glands.


How do they work?

Well, as the glands secrete the fluid, the sacs fill up. Then, when the dog goes to the toilet, the faeces passing by compress the gland between the faecal matter and the bone of the pelvis, squeezing out some of the liquid. This coats the faeces, giving them a scent that to dogs is like the best cologne or perfume. To us, however, it smells like rotten fish!


So what can go wrong?

By far the most common problem is that the glands don’t empty properly, which can cause anything from a minor annoyance to a major infection. The other possibility is a cancerous growth in the gland – although this is pretty rare (about 2% of all skin tumours) it tends to be quite aggressive, so is always something we check for in an older dog.


1) Anal sac impaction

This is by far the most common problem – essentially, the anal sacs don’t empty properly, for some reason. The most likely underlying cause is a mild bout of diarrhoea – wet soggy faeces don’t squeeze the sacs as well as nice firm ones, so the fluid doesn’t get emptied out. Normally, it will drain once the faeces return to normal consistency; however, occasionally they get so full and so stretched that they can’t empty out. This is uncomfortable for the dog, and often they’ll try to empty them by rubbing their bottoms on the floor or the furniture, along with periodic licking.


2) Anal sac infection

Once an impaction becomes established, it isn’t uncommon for bacteria to set up home inside, resulting in infection. This causes increased pain and local swelling which may make it even harder for the gland to empty. The inflammation may mean that attempts to empty the sac (by the dog, who may by now be frantically licking the area) result in bleeding.


3) Anal sac abscesses

If the infection can’t come out through the sac’s normal draining ducts, pus starts to build up in it, until eventually, the gland ruptures, draining out through the skin outside the anus. This will resolve the infection, but does raise the risk of an anal fistula (an unnatural opening) forming in the medium term.


Treatment for an anal sac impaction is easy – bring your dog into is and one of our vets will empty (or “express”) the sac. They’ll do this by putting a finger up the dog’s bottom (with a glove on, of course) and gently squeezing to empty it, replicating the normal function. If the sac is too swollen and infected, however, they may be unable to empty it, and may need to give a course of antibiotics and anti-inflammatories to bring the swelling down so it can be expressed in a few days time.

Anal abscesses need more aggressive treatment, with flushing of the area and antibiotics, to make sure the infection is completely resolved. Occasionally, surgery is required as well.


Most dogs will develop an anal impaction at some point in their lives, and usually, getting it expressed will resolve the problem. However, some dogs are very prone to repeated impactions, probably because of the exact way their sacs drain (or rather, fail to). In mild cases, it may be possible to use a fibre supplement (e.g. ProFibre) to firm up the faeces so they squeeze the sacs more effectively. In the most severe cases, though, surgical removal of the anal sacs is required.


Anal sac adenocarcinoma

This is a malignant tumour of the anal sacs, and most commonly presents as an uncomfortable (but not generally painful) lump in one of the sacs. Anal sac tumours are also prone to causing problems with the dog’s ability to regulate their blood calcium, so they are sometimes diagnosed following a blood test for something else that picks up abnormally high calcium levels. These need urgent surgery, and sometimes chemotherapy or radiotherapy as well.


If your dog seems to be having bottom problems, make an appointment to get it checked out by one of our vets!