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Why do dogs scoot or chase their tails?

Updated: Jun 22, 2021



There are times that your pet starts scooting across the floor, rubbing his/her rear end, licking his/her bottom more than usual. When you check, the area around the anus is swollen and inflamed. This swollen area around the anus is occupied by what are called anal glands or anal sacs.

What are anal glands or anal sacs?


Anal glands are part of a normal pet's anatomy. These are two small pockets located on either side of the dog's bottom, opening into the surface of the anal opening at about the 4 and 8 o'clock positions.

Anal glands (sacs) location around the anal region

What is the importance of anal glands (anal sacs)?


The anal glands or sacs produce a strongly scented substance that is deposited on the faeces. The passage of faeces usually results in emptying of the glands in healthy dogs. Anal sacs may also occasionally be emptied in times of distress or panic, e.g. a dog fight or a road traffic accident, resulting in a strong smell coming from the injured dog. The secretion usually has an unusual fishy odour, unpleasant to the human nose.

The importance of the glands and their contents include:-

1. Territorial marking in dogs.

2. The strong scent, designed to last a long time in the environment, is part of how dogs communicate with one another.

What causes anal glands (sacs) problems?


The glands are designed to excrete a smelly fluid during defecation. They give a particular scent to the stool. When a pet doesn't have regular bowel movements or only a small stool volume, the following can happen:-

Blocked or impacted anal sacs or glands:

Blocked anal gland (sac)

Glands become blocked or impacted, most commonly due to the retention of anal sac secretions often leading to inflammation and infection. Possible causes include:-

  1. The ducts leading to the anal surface are too narrow

  2. Diets, leading to too loose consistency of the dog's faeces

  3. External anal sphincter dysfunction,

  4. Undersized anal sac ducts,

  5. Tapeworm heads lodged in the anal sac duct orifice.

The problem is more common in small dogs. When they get full, they cause discomfort showing clinical signs as:

  1. Licking and biting at the tailhead region of the anal area excessively.

  2. Chasing the tail.

  3. Sitting down abruptly and clamping the tail.

  4. Dragging the bottom along the ground ('scooting') - often misunderstood by owners as a symptom of worms.

  5. General irritability and restlessness.

  6. Pain on defecation.

  7. Redness and swelling over the anal sac region.

  8. Faecal tenesmus.

Infected anal sacs or anal sac abscess

Anal gland abscess (ulcerated)

The anal sacs can become infected, possibly as a result of chronic blockage (see above). If an abscess develops, the symptoms can be severe. All the signs of anal sac blockage may be present and the affected dog may be very uncomfortable and even aggressive if the hindquarters are approached or touched. The abscess may burst out to the surface, producing a foul-smelling or bloody discharge. Symptoms usually ease off at this point as pressure is released and pain decreases.

Anal gland carcinoma

In some dogs, the glandular tissue in the anal sacs develops into a tumour (cancer). Since the disease is more common in some breeds of dogs, it is suggested that genetic factors are involved but no one really knows for sure why some dogs develop the disease. In many cases, this is the only site in which the tumour is growing but sometimes the tumour may spread to the lymph nodes or via the bloodstream to places like the lungs, liver and spleen.

Anal sacculitis

Anal sacculitis refers to the Inflammation and enlargement of the anal sacs and is associated with pain and discomfort to the perineal region. Sacculitis is characterised by a thin greenish or creamy yellow secretion some- times flecked with blood. The causes are similar to those of anal gland impaction. The clinical signs include:-

  1. Faecal tenesmus,

  2. Redness and swelling over the anal sac region.

  3. Palpation of the anal sacs evokes a great deal of pain.

  4. A thin, sanguineous and sometimes purulent discharge is seen when sacs are expressed.

  5. Severe cellulitis or abscess formation.

Anal sac disease is a common problem in dogs but infrequent in cats.

How are anal sac problems treated?

  1. Periodic emptying of the anal glands by a veterinary surgeon is required every 4-8 weeks.

  2. Changing the composition of the diet helps. Adding more fibre to promote a bulkier stool is often recommended.

  3. If an infection is present, a course of antibiotics may be needed.

  4. The anal sacs may also be flushed with saline or dilute antiseptic solutions under sedation or anaesthesia to help eliminate the problem.

  5. Abscesses may require surgery to aid drainage and resolution of the infection, together with a course of antibiotics and, often, painkillers.

  6. Persistent anal sac problems may be treated by surgical removal of the anal sacs.



Gallagher, A. (2021). Anal Sac Disease in Dogs and Cats. In M. S. Corp., Merck Veterinary Manual. Kenilworth, NJ, USA: Merck Sharp & Dohme Corp. Retrieved from

Halnan, C. R. (1976~). Therapy of anal sacculitis in the dog. Journal of Small Animal Practice, 17, 685-691.

Halnan, C. R. (1976a). The frequency of occurrence of anal sacculitis in the dog. Journal of Small Animal Practice, 17, 537-541.

Halnan, C. R. (1976b). The diagnosis of anal sacculitis in the dog. Journal of Small Animal Practice, 17, 527-535.

Robson, D. C., Burton, G. G., & Lorimer, M. F. (2003, Jan-Feb;). Cytological examination and physical characteristics of the anal sacs in 17 clinically normal dogs. Aust Vet J., 81(1-2), 36-41. doi:10.1111/j.1751-0813.2003.tb11418.x.

van Duijkeren, E. (1995, January). Disease conditions of canine anal sacs. Journal of Small Animal Practice, 36(1), 12-6. doi:10.1111/j.1748-5827.1995.tb02756.x.

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