Anal cancer in dogs: signs, diagnosis and care

A dog may develop a mass in the anal sac, skin around the anus or nearby tissues. Possible changes include swelling beside the anus, straining to pass stool, scooting, licking, bleeding or a change in stool shape. Anal tumours can also be found during a routine veterinary examination before the dog seems unwell.

The term anal cancer does not name a single disease. Tumours can arise from anal sac glands, skin glands or other local tissues, and their behaviour differs. Infection, an abscess, an impacted anal sac and benign growths may cause similar outward signs, so appearance alone cannot establish the cause.

The veterinarian may examine the rectum and anal sacs, sample the lump with a needle or biopsy, and order blood tests. Imaging of the abdomen, chest or local area can help show the mass boundaries and whether nearby lymph nodes or other organs need attention. A laboratory tissue diagnosis guides treatment choices.

Book a veterinary appointment for any persistent lump, discharge, bleeding or difficulty passing stool. Note when the change began, whether it is growing and how the dog's appetite, thirst, urination, stools and activity have changed. Prevent licking if the area is raw, but do not squeeze a mass or apply human creams.

Management is tailored to the tumour type, location, extent and the dog's overall health. Options may include surgical removal, radiation treatment, systemic medicine or comfort-focused care. Ask how each option could affect bowel control, wound care, pain relief and daily quality of life.

Contact a veterinarian promptly if your dog repeatedly strains, cries during defecation, has ongoing bleeding, develops a rapidly enlarging swelling or becomes unusually weak. Emergency assessment is appropriate if the dog cannot pass stool or urine, collapses, has uncontrolled bleeding, repeatedly vomits or cannot keep water down.

Ask which tissue the tumour arose from, whether a pathology sample is needed, what imaging could change the plan and whether lymph nodes appear involved. It is also useful to discuss pain control, likely toileting needs after treatment and which changes should trigger an urgent return visit.