A bum note

A question I get asked a lot (often during coffee break):

If a dog is on a good diet why does he regularly require his anal glands emptying? And is there any truth in 'once he has had them emptied as a puppy, he will need them emptying for the rest of his life?

Thanks,

Tony C, by email




Alison Logan, vet, advises...

There are two anal sacs, as they should strictly be termed because they do not have a lining of secretory cells. They lie just inside the anus at approximately 4 and 8 o’clock if you were to imagine the anus as the face of a clock. They fill with a foul, often fishy smelly fluid or thicker secretion which should be naturally emptied onto the faeces as they pass through the back passage. They can also be released when frightened, hence the smell you may notice if dogs have a confrontation or are scared.

There are so many stories and myths about anal sacs, and a true, full explanation has not yet materialised as far as I am aware! Certainly, I will always check the anal sacs if a dog presents with an ear infection or skin infection, and they are invariably full. Whether that is coincidence is hard to know. There are vets who boast of having never emptied an anal sac during their professional lives – lucky them! I do seem to have days when most consultations have involved this less than pleasant task. Sometimes there is an infection within the anal sac, indicated by the presence of blood in the material expressed, and occasionally a dog will present in a great deal of pain because of an abscess. Would these have been prevented if the anal sacs had been more regularly emptied? – who can tell?

Dogs who drag their rears across the ground, or scoot, often have full anal sacs. Some poor individuals need their anal sacs emptied on a regular basis, others once in a blue moon. Having the anal sacs emptied as a puppy is not a red light to me for a lifetime of impacted anal sacs – the gut of a puppy is developing, and the faeces are often variable, especially if there is a change in diet (intentional or inadvertent such as through scavenging!). Sometimes, though, the anal sacs are empty and the scooting is a reflection of an itchy backside associated with allergic skin disease, so a young adult showing perineal irritation for the first time may indeed experience this for the rest of his or her life.

I have also noticed that an older dog may start to need the anal sacs emptying, which I attribute to changes in the stance adopted when passing faeces, secondary to joint pain and arthritis.

Increasing the fibre content of the diet may help anal sac impaction. This is achieved by adding bran (not high fibre breakfast cereals which have other ingredients) or a specific canine high fibre formulation.