Cats, dogs, ferrets, and most animals have pouches on each side of the anus. These are called anal sacs. A foul-smelling, brown liquid is secreted from the sac lining whenever the animal defecates. Although the exact function is unknown, it can be that the animals mark their territory and communicate this to other animals in the area by secreting this liquid.

When these sacs become inflamed, blocked, or have an infection, the animal tends to rub its anus on grass or similar surfaces, as well as lick the affected area. This should alert you to the fact that the animal is experiencing discomfort and should be taken for a checkup. Usually, a blockage can be resolved by the veterinarian pushing excess fluid out of the sacs. This might need to be done occasionally.

It is rare, but these sacs around the rectum can develop tumours. They are known as apocrine gland adenocarcinomas. Their presence is serious because they grow into the tissue around the anus. These growths can then spread elsewhere is the body. Tumours usually exist in one of the two glands. Tumours found in two glands concurrently are very rare. When these tumours are present, elevated calcium levels found in the blood (hypercalcemia) occurs in one quarter of the cases. This can lead to kidney failure in the affected animal.

This medical condition occurs in both genders of dogs, where one gender is not less prone than the other. The conditions can present in every breed of dog; however, Spaniels tend to be more prone. Most dogs experience this discomfort at approximately ten years of age. Cats are infrequently affected.

Signs and Symptoms:

There are many signs to show that your animal has a tumour of the anal sac. These symptoms are varied and can present in different combinations. First signs are swelling of the perianal area. On examination, a lump might be easy to feel in the area. Constipation can be present, as well defecation being painful and difficult. On examining the excrement, it may be laced with blood. As mentioned earlier, certain cases can cause failure of the kidneys. This is caused by high calcium levels which causes what is known as malignancy hypercalcemia. If this is the case, the dog will be extremely thirsty and need to urinate more frequently. The animal may throw up and lose its appetite. Extreme weakness and fatigue may occur.


Your veterinarian will suggest tests and imaging be done in order to make a proper diagnosis. These tests will also clarify the clinical status of your dog and its general health. They are also be used to check for metastasized growths and spreading of the cancer to lymph nodes or other organs.

Firstly, a sample from the tumour will be taken by inserting a needle into the lump to get some cells. This is called a biopsy. The sample will be analyzed for any abnormalities that can be seen under a microscope. It will show whether the lump is caused by swelling and infection, or if it is cancerous. The next test will be to take blood samples which will determine if kidney failure has been caused by high calcium levels. Infection will also show in a high white blood cell count.

Radiographic imaging can be done to see if there are any secondary growths in the heart or lungs. An ultrasound will show lymph enlargements or signs of cancer that has spread to other abdominal organs. If there are secondary cancers, treatment is more complicated and drops the prognosis rate dramatically.


You may be referred to a specialist surgeon so that you can weigh up various treatment options.

Operating is usually required and is proven to be the only way to extend the lifespan of the animal. The procedure involves an incision being made next to the anus, exactly where the tumour is located. The tumour is removed with as little tissue being excised as possible due to the small structure of the annual opening. If the tumour is very big, extra tissue surrounding the anus might be excised as well. Since the lining of the anus is so thin, it may not always be possible to remove the entire mass.

Should there be any lymph nodes that are enlarged they need to be excised by performing an abdominal operation concurrently. Node enlargement occurs in approximately half of the cases.

If hypercalcemia has occurred, fluids and medication are given before the surgery to stabilize the dog prior to surgery. The calcium levels will need to be returned to normal. Sometimes, failure of the kidneys is permanent. Radiation therapy and chemotherapy may be needed afterwards. This can increase your pet’s lifespan.

Aftercare and Outcome:

The animal is usually kept in hospital for s day or two. You will be given an appointment date where your dog’s progress is monitored, and any stitches are removed. You will also be given pain tablets so that you can manage the dog’s pain at home.

The dog will have a collar which restricts movement for about two weeks post-surgery to prevent it from biting or licking the wound site. Laxatives may be needed until your dog has healed. Try to limit movement of the dog so that healing can take place.

Complications post-surgery:

Complications that might occur are infections of the operation incision, dehiscence (or breakdown) of the wound, and incontinence. Incontinence is usually of a temporary nature. Kidney damage can also be permanent.

The type of treatment that was used on apocrine gland adenocarcinoma usually determines the prognosis of the dog. The tumour size that was found can affect the success of the procedure as well. If hypercalcemia occurred kidney damage will be assessed, and additional treatment may be necessary to extend the dog’s life. Whether lymph nodes were affected can also influence the outcome.

The anal sacs should be examined in your dog’s regular checkups. If problems are detected early, survival rates are greatly improved.

Anal sac adenocarcinoma tumour removal: