DOGS · Condition guide
Anal sac disease in dogs: impaction, infection, and rupture
Anal sac disease affects roughly 1 in 20 dogs each year — high enough to be in the UK top-10 of primary-care diagnoses, but most owners only learn about it the first time their dog starts scooting across the carpet. The sacs sit at the 4 and 8 o'clock positions next to the anus and normally empty during defecation. When they don't, the secretion thickens, becomes irritating, and eventually infected (anal sacculitis) — and in the worst cases ruptures through the skin as a painful abscess.
Repeated impactions are common in small breeds, overweight dogs, and dogs with soft stools. Most cases resolve with manual expression and (if infected) antibiotics. Less common but important: anal sac adenocarcinoma is a malignant tumour that produces a firm mass at the sac site — every persistent or unilateral swelling deserves a careful exam, not just another expression.
What vets typically check for
- Digital rectal exam to assess sac size, contents, and any firm masses.
- Cytology of expressed contents if infection or atypia is suspected.
- Fine-needle aspirate of any firm swelling — rule out anal sac adenocarcinoma.
- Bloodwork including ionised calcium when malignancy is suspected (paraneoplastic hypercalcemia).
- Surgical sacculectomy for chronic recurrent disease or confirmed neoplasia.
Not a replacement for veterinary care. Use this to walk into the conversation prepared, not to self-diagnose.
Real cases from the veterinary literature
Peer-reviewed reports our semantic search surfaces for Anal sac disease in dogs. Click into any case for the full abstract — or run a personalised search with your pet's exact details.
- Cytologically atypical anal sac adenocarcinoma in a dog.
Veterinary clinical pathology · 2012 · Japan
A 10-year-old female Shetland Sheepdog had a lump near her anus and was straining to defecate. Tests showed two different types of abnormal cells in the mass, which were loosely grouped together. The mass was made up of gland-like structures and had some secretory material inside. Based on the tests and the location of the mass, the diagnosis was anal sac adenocarcinoma, a type
- A Cross-Sectional Study on Canine and Feline Anal Sac Disease
Animals · 2021 · CH
This study looked at anal sac disease in dogs and cats, which is a condition that isn't caused by tumors. It found that about 15.7% of dogs and only 0.4% of cats have this issue, with certain factors like diarrhea, skin problems, and being a small breed dog or an overweight dog increasing the risk. The diagnosis is usually made by checking for specific symptoms and examining th
- Temporally separated bilateral anal sac gland carcinomas in four dogs.
The Journal of small animal practice · 2013 · United States
Anal sac gland carcinoma arising from the apocrine secretory epithelium in the anal sac wall, is locally invasive and highly metastatic.
- Canine Apocrine Gland Anal Sac Adenocarcinoma: A Review.
Topics in companion animal medicine · 2022 · United States
Apocrine gland anal sac adenocarcinoma (AGASAC) is a type of cancer that can occur in dogs, making up about 17% of cancers found near the anus. Dogs with this condition may show signs like trouble passing stool due to the tumor or swollen lymph nodes, and they might also experience high calcium levels in their blood, which can cause various health issues. The main treatment usu
- Evaluation of an anal sac adenocarcinoma tumor in a Spitz dog.
Asian Pacific journal of tropical biomedicine · 2013 · United States
A 9-year-old neutered male Spitz dog was having trouble with straining to poop and was also constipated. He had a lump near his anus and had been drinking and peeing a lot more than usual. Blood tests showed some unusual results, including high cholesterol and calcium levels, which can indicate health issues. After examining the cells from the lump, the diagnosis was an anal sa
Frequently asked questions
- How often should I have the glands expressed?
- Only when there's a clinical sign — scooting, licking, swelling, or discomfort. Routine prophylactic expression in dogs that aren't symptomatic isn't recommended; it can actually irritate the sacs and trigger problems.
- Could it be cancer instead of just impaction?
- Yes. Anal sac adenocarcinoma is uncommon but serious. Warning signs are a firm, unilateral swelling that doesn't go away with expression, persistent straining, or high blood calcium on bloodwork. Always have a persistent or asymmetric mass at the sac aspirated.
- Does diet help?
- Sometimes — adding fibre (pumpkin, psyllium, or a high-fibre prescription diet) bulks the stool so it puts more pressure on the sacs during defecation and helps them empty naturally. Weight loss helps in overweight dogs.