Splenic Haemangiosarcoma

Splenic haemangiosarcoma is a serious cancer that affects the spleen in dogs. It develops from cells associated with blood vessels and tends to bleed easily. Some tumours cause small, intermittent bleeds. Others rupture suddenly and cause life-threatening blood loss.

Because the signs can be subtle at first, and because the tumour can spread before it is found, understanding this disease can help owners notice problems earlier and make informed decisions.

Splenic haemangiosarcoma is a malignant cancer that develops from cells associated with blood vessels in the spleen.

The tumour contains abnormal, fragile blood vessels and tends to bleed easily. It may bleed slowly over time or rupture suddenly, causing a large amount of blood to collect inside the abdomen.

Splenic haemangiosarcoma is also an aggressive cancer that tends to spread early. Cancer cells may already be present elsewhere in the body by the time the tumour is diagnosed, even when no visible metastases are found on the scans.

When the tumour is small and the bleeding is mild, there may be almost no symptoms.

The patient may occasionally seem quieter or less energetic than usual. These changes can resolve quickly if a small bleed stops and the circulation stabilises.

As the tumour becomes larger or the bleeding becomes more significant, the symptoms usually become more noticeable.

One sign to look for is an abdomen that appears gradually larger or more bloated, even though the patient has not gained weight and may be losing weight elsewhere.

Other symptoms can include:

A patient may be weak or quiet for several hours and then appear almost normal again. This can happen when the tumour has a small bleed that temporarily stops.

Bring your dog to a veterinarian immediately if your dog:

These signs may mean that the tumour has ruptured and the patient is losing a significant amount of blood into the abdomen.

A large splenic mass may sometimes be felt during a physical examination. It may also be visible on an abdominal X-ray.

However, an abdominal ultrasound is usually the most useful test. It allows the veterinarian to examine the spleen, assess the size and appearance of the mass and check whether blood has collected inside the abdomen.

The rest of the abdomen should also be examined carefully, particularly the liver, to look for any visible signs that the cancer has spread.

Blood tests may show anemia, a low platelet count or other changes associated with blood loss. Blood-clotting tests may also be recommended, particularly if the patient is bleeding.

Further staging tests may include:

Scanning the heart is useful for checking for a concurrent cardiac mass or possible spread involving the heart before surgery is considered.

An ultrasound can show that a splenic mass is present, but it cannot reliably confirm that the mass is haemangiosarcoma. Benign splenic haematomas and other non-cancerous growths can look very similar.

The definitive diagnosis is usually made after the spleen has been surgically removed and the mass has been sent for histopathology. This means that a veterinary pathologist examines the tissue under a microscope.

The main options are surgery, chemotherapy and palliative care. The most appropriate choice depends on whether the tumour has ruptured, whether there is visible spread and how stable the patient is.

If the tumour has ruptured, the immediate priority is to stabilise the patient and manage the blood loss.

Treatment may include:

The treatment needed will depend on the amount of blood lost, the patient's blood pressure, red blood cell count and overall condition.

Surgical removal of the spleen is known as a splenectomy.

Surgery is most commonly recommended when staging has not found obvious metastases in the liver or elsewhere in the body, and the patient is well enough to undergo anaesthesia.

Removing the spleen stops the bleeding from the primary tumour and provides the tissue needed for a definitive diagnosis.

If the mass is benign, surgery may be curative.

If the mass is haemangiosarcoma, surgery removes the primary tumour but does not usually cure the cancer. Microscopic cancer cells may already be present elsewhere, even when the liver, chest and heart scans appear clear.

When visible metastases are already present, surgery is less likely to provide meaningful additional time. However, in selected patients, emergency surgery may still be considered to control active bleeding.

Chemotherapy is usually recommended after the spleen has been removed and haemangiosarcoma has been confirmed.

Doxorubicin-based chemotherapy is most commonly used. Its purpose is to slow the growth of microscopic cancer cells that may remain elsewhere in the body.

Chemotherapy may extend survival, but it does not usually cure splenic haemangiosarcoma.

Veterinary chemotherapy protocols are planned with quality of life in mind. Many dogs tolerate treatment reasonably well, although possible side effects include:

Chemotherapy may sometimes be considered when surgery is not possible. However, chemotherapy alone does not remove the splenic tumour or eliminate the risk of another internal bleed.

Some families decide not to proceed with surgery or chemotherapy. In these patients, treatment shifts towards maintaining comfort and reducing blood loss where possible.

Depending on the individual patient, medications such as Yunnan Baiyao, tranexamic acid and vitamin K may be considered.

These medications can sometimes be helpful in reducing blood loss during smaller, intermittent bleeds. However, they do not all work in the same way and are not suitable for every patient.

Tranexamic acid helps to slow the breakdown of blood clots. Vitamin K is most likely to be helpful when there is a vitamin K deficiency or another vitamin K-responsive clotting problem.

The choice of medication and dose should be decided by the veterinarian after considering the patient's blood results, other illnesses and current medications.

These medications do not shrink the cancer or prevent the tumour from rupturing. They also cannot control a major internal bleed.

Other parts of a palliative care plan may include:

A patient who collapses, develops pale gums, becomes suddenly weak or starts breathing rapidly still requires immediate veterinary attention.

The prognosis remains guarded even when no metastases are visible at diagnosis.

In one study of dogs with stage I or II splenic haemangiosarcoma that appeared confined to the spleen at surgery, the median survival time after splenectomy alone was 86 days. The mean survival time was 116 days, and approximately 6% were alive one year later.

A larger study subsequently reported a median survival of approximately 1.6 months for dogs treated with splenectomy alone across all stages.

This is why a clear liver scan or chest X-ray does not mean that surgery will be curative. The cancer may already have spread at a microscopic level.

When splenectomy is followed by chemotherapy, current reviews generally report a median survival time of approximately four to seven months. A veterinary oncology consensus review reported a mean survival time of approximately 170 days, or five and a half months.

In a study of dogs with no visible metastases that underwent splenectomy and chemotherapy, median survival was 238 days when chemotherapy began within 21 days of surgery. It was 146 days when chemotherapy began later. This does not mean every patient must begin chemotherapy within that exact timeframe, but it supports discussing treatment promptly once the patient has recovered from surgery.

Even with surgery and chemotherapy, fewer than 10% of patients are generally alive one year after diagnosis.

These figures describe groups of dogs and cannot predict exactly how long an individual patient will live. The outlook also depends on:

It usually has not appeared suddenly.

A splenic haemangiosarcoma may have been growing quietly for months before it becomes large enough to be noticed by the family or felt during a physical examination.

Most patients compensate remarkably well for gradual blood loss. They may continue eating, walking and behaving normally while the tumour is bleeding slowly.

By the time the abdomen looks enlarged or the patient becomes noticeably weak, the tumour may already be quite large. For many patients, the first obvious sign is a significant bleed.

No. Benign splenic haematomas and other non-cancerous growths can also rupture and bleed.

These growths may look very similar to haemangiosarcoma on an ultrasound. If the mass is benign, removing the spleen may be curative. Histopathology is usually needed to determine what type of mass it is.

Sometimes.

For my older patients, particularly predisposed breeds such as German Shepherds, Golden Retrievers and Boxers, I advise routine abdominal ultrasound screening.

An ultrasound may identify a splenic mass while it is still relatively small and before it has ruptured. Finding a mass at this stage gives us more time to assess the patient and consider the available treatment options.

An ultrasound cannot usually determine whether a mass is benign or malignant, and a normal result does not guarantee that a tumour will not develop later. The screening interval should be individualised according to the patient's age, breed, health and previous results.

Dr Kelly Yeo graduated from the University of Melbourne in 2009 and has extensive experience in companion animal medicine, with a special interest in geriatric care, chronic disease management, palliative care and canine longevity.

Her work focuses on helping dogs live longer, healthier and more comfortable lives through early detection, thoughtful nutrition, practical preventive care and compassionate support for owners.