Anal Sacs

What are anal sacs?

The anal sacs are glands located on either side of the anus at the 8:00 and 4:00 positions. They are positioned within the muscle of the anal sphincter. They connect to the outer skin of the anus by means of small canals or ducts. Anal sacs produce and store a smelly dark brown fluid. Anal sacs are a kind of scent gland. The anal sacs can be emptied if the dog is very frightened or sometimes during normal defaecation. If the sacs are rarely emptied, the fluid builds up, solidifies, and becomes an ideal environment in which bacteria can grow.

What can go wrong with anal sacs?

1. Impaction: When the fluid becomes thick and solidified, it is hard for the gland to empty normally. This is called impaction.

2. Infection: When bacteria grow in this material producing a yellow or bloody pus.

3. Abcessation: If an infection builds up, it can involve surrounding tissues, causing heat, pain and swelling. The pus can burst through the skin, causing a bloody pus discharge and a visible sore

4. Cancer : Anal sac tumours can occur in dogs and are often malignant.

What are the signs of anal sac disease?

Signs your dog is not happy with their anal sacs are:

1. Scooting or dragging the anal area.

2. Excessive licking around the tail.

3. Pain around the tail or anus.

4. Swelling or redness at the side of the anus.

5. Bloody or yellow discharge from sores near the anus.

6. Difficulty or pain when passing stools.


For Impaction, the vet will gently squeeze out (express)the contents of the anal sac. For infection, the sacs must be expressed and antibiotics administered to kill the bacteria. If there is an abcess, this will need surgical draining by your veterinary surgeon and antibiotics administered.

Occasionally lumps near the anus can be tumours or hernias. The vet may collect a needle biopsy or a surgical biopsy to diagnose the type of tumour. The treatment and prognosis (long term outlook) will depend on the type of tumour.

Surgical treatment for recurrent disease:

It is not uncommon for dogs to have recurrent anal sac disease. Some breeds of dogs, such as Poodles, commonly have this problem. If a dog has several episodes of anal sac disease, the anal sacs can be removed surgically. Because these sacs are virtually unused, there is no loss to the dog. It is the only way to permanently cure the problem.

Are there any complications of the surgery?

Surgery requires general anaesthesia which always carries some degree of risk, whether the patient is a dog or a person. However, modern anaesthetics make this risk very minimal for dogs that are otherwise healthy.

Some dogs will experience lack of good bowel control. They may drop faecal balls as they walk. This occurs because the nerves that control the anus are very near the anal sacs and may be damaged during surgery. However, this is almost always a temporary problem that will usually resolve in a few weeks.

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