Anal sac diseases


The anal sacs (also called anal glands) are two small structures that are positioned under the skin, one on each side of the anus. The inner lining of each sac produces a substance (or discharge) that is released through a small opening near the anal opening. This substance has a strong, unpleasant odor, and it can vary in color and consistency.  

Under normal circumstances, it is released when there is pressure against the anal sacs as the dog defecates. We can also observe the spontaneous release of this discharge when a dog is nervous or excited. A likely purpose of this substance is to serve as territorial scent marker.  

What problems are associated with anal sacs? 


One of the most common problems is impaction, which occurs when the sacs do not empty adequately. The contents of the sac will become thicker, and as the anal sac continues to fill, it will become enlarged and uncomfortable.  

Anal sacculitis 

Impaction can result in inflammation or infection in the anal sac, referred to as anal sacculitis.   This process can lead to abscess formation, and even cause the anal sac to rupture, releasing pus and even blood.  

Anal sac adenocarcinoma 

A very serious disease of the anal sacs is a type of cancer known as anal sac adenocarcinoma

What are signs of a problem? 

One of the most frequent signs is what we call “scooting,” which is when dogs drag their rear end along the floor, lawn or another surface. Additionally, dogs will often lick or bite themselves in the anal area.  

Owners will notice a characteristic “fishy” odor or see traces of discharge on the floor or other surfaces.  

Dogs may also hold their tail down, be reluctant to defecate, strain during defecation or act sensitive in the hind end area. Swelling, redness or discharge (which may be bloody) may be noted next to the anus.  

Are there any risk factors? 

Problems can occur across all breeds. However, smaller dogs tend to be affected more often than larger breed dogs. Among small breeds, one study found that Chihuahuas were the most commonly affected. For large breeds, German Shepherd Dogs may be over-represented.  

There is no predisposition based on sex, but it is typically seen in dogs over 1 year of age. Food allergy dermatitis and atopic dermatitis may contribute to anal sac disease. Other risk factors include anatomic abnormalities of the anal sacs, chronic diarrhea, constipation, obesity and a low-fiber diet.  

What can you do to help your dog? 

Your veterinarian will inspect the area and perform a digital rectal exam. Some dogs will benefit from sedation, as it may be an uncomfortable procedure. The anal sacs can be manually expressed if they are impacted. A sample of the discharge may be examined under the microscope for the presence of bacteria, yeast, white blood cells or red blood cells.  

If anal sacculitis is suspected, treatment will involve flushing the anal sac with saline or an antiseptic solution. Then a prepared solution that has a combination of antibiotics and a corticosteroid can be infused into the sac.  

If an abscess is present, additional sedation or anesthesia may be needed to ensure your dog’s comfort. The area will be shaved and cleaned, and if the abscess hasn’t already ruptured, it can be drained. Your vet will prescribe antibiotics and pain medications, and an Elizabethan collar can be used to prevent your dog from licking the area while it heals.  

For dogs with recurrent issues, your veterinarian may advise that the anal sacs be palpated and expressed periodically to help prevent impaction. In more severe cases, removal of the anal sacs (anal sacculectomy) may be recommended — but the risks of infection and fecal incontinence need to be taken into consideration.  


The prognosis for dogs with non-cancerous anal sac disease is good. Recurrences may be minimized with regularly scheduled veterinary exams and by addressing underlying conditions.   

Weight loss and the addition of fiber to the diet can be beneficial. Removal of the anal sacs can be considered for dogs with recurrent disease.