Anal sac disease in dogs (impaction, inflammation, abscess)
Dogs have two small pouches on either side of the anus called anal sacs. They contain a brownish fluid with a very strong odor, normally expelled in small amounts with bowel movements, and serve a marking function. When this fluid does not...
What is it?
Dogs have two small pouches on either side of the anus called anal sacs. They contain a brownish fluid with a very strong odor, normally expelled in small amounts with bowel movements, and serve a marking function.
When this fluid does not drain properly, the pouch fills up and becomes blocked—this is impaction, the most common form. The pouch may then become inflamed, then infected and form an abscess: a painful swelling, red or purplish in color, beside the anus, which sometimes ruptures.
This is a very common problem in dogs, especially small breeds, and tends to recur.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
The dog scoots its rear along the ground.
It licks or nibbles the anal area or underside of the tail persistently, or turns abruptly toward its hindquarters.
The area beside the anus is red or swollen; a lump may appear on one side.
A strong, unpleasant odor comes from the hindquarters, sometimes with traces of brownish fluid where the dog has sat.
With an abscess: a warm lump that is red-purplish and painful, then a small wound draining beside the anus, with bloody or purulent discharge.
Discomfort or straining during bowel movements; some dogs hold back and become constipated.
A dog with an abscess may be lethargic and run a fever.
To distinguish: a hard, minimally painful lump beside the anus in an older dog should raise concern for an anal sac tumor.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
Poor drainage of the sacs, for example when feces remain too soft for a period of time and no longer compress the pouches as they pass.
Thickened anal sac fluid that does not drain well.
Inflammation of the skin around the anus.
Bacterial infection, which turns simple impaction into an abscess.
In many dogs, no specific cause is found.
Small breeds: large breeds are affected less often.
Previous episodes: recurrence is common.
Prolonged soft stools.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The vet examines the area around the anus and palpates the anal sacs, usually through gentle rectal palpation.
He or she observes the appearance of the fluid expressed: normal, thick, bloody, or purulent.
The vet distinguishes anal sac disease from other causes of anal discomfort: tapeworms, allergies that also cause ear and paw itching, diarrhea, tumors.
In an older dog, a firm mass in an anal sac prompts investigation for a tumor: the vet may then recommend testing the mass and bloodwork.
In case of abscess, the vet assesses the extent of infection and takes the temperature.
Treatment
An impacted sac is emptied by the vet, sometimes under sedation if the area is very painful.
In case of inflammation or infection, the sacs may be flushed and treatment is prescribed: antibiotic and anti-inflammatory as needed, applied locally or given by mouth.
An abscess is opened, cleaned, and treated; home care such as warm compresses may be recommended by the vet.
The underlying cause is addressed, particularly persistent soft stools.
If problems recur repeatedly, surgical removal of the anal sacs may be suggested.
Do not attempt to puncture or empty a swelling next to the anus yourself: the area is painful and improper handling can worsen the infection.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
There is no reliable prevention.
Have diarrhea or soft stools that persist treated promptly.
In a dog that has had problems before, the vet may recommend regular anal sac emptying; how often this is done should be decided with your vet.
In a dog that has never had a problem, routine emptying is not necessary.
A dog that scoots or licks the anus constantly should be examined.
Possible complications
Abscess rupturing next to the anus.
Recurrence of impaction or infection.
Constipation when the dog avoids defecating because of pain.
Fistula, a small channel that continues to drain when infection persists.
When to see a veterinarian
Your dog strains without passing anything and is not urinating: seek emergency care.
You see a warm, red-purple swelling or a draining wound next to the anus: consult the same day.
The dog has fever, is lethargic, and has a swelling near the anus: consult the same day.
The dog scoots or licks the anus persistently.
The dog has pain or strains prolonged during defecation.
You feel a firm mass next to the anus, especially if the dog is drinking and urinating more than before.
Prognosis
The prognosis is good: most cases of impaction and abscess heal well with appropriate care.
Recurrence is common; it is managed by treating the underlying cause, through regular emptying or, if it recurs, by surgery.
Frequently asked questions
My dog is dragging its rear end: anal glands or worms?
Both are possible. If you see small white grains resembling rice around the anus, on its bedding, or in its stool, these are likely tapeworm segments. A lump, redness, or a draining wound right next to the anus points more toward anal gland issues.
He also scratches his ears, paws, or belly: is it still the anal glands?
Itching in several areas suggests an allergy, either skin-related or food-related. It can coexist with an anal sac problem: only a veterinary examination can distinguish between the two.
A lump next to the anus—is it necessarily an abscess?
No. An abscess appears within a few days; it is warm, reddish-purple, and very painful. A hard lump that is not very painful in an elderly dog, especially if it drinks and urinates a lot, should prompt investigation for an anal gland tumor. In both cases, a veterinarian should be consulted.
Should I regularly empty my dog's anal sacs?
Not in a dog that has never had a problem. In a dog prone to impactions, regular emptying may be helpful: the frequency should be decided with your veterinarian.
References
Content reviewed by the TunisieVet editorial team · Updated 10 October 2026
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