Pete the Vet: I witnessed the death of a Golden Retriever with a malignant tumour

Do animals really need their spleen?

Pete the Vet: In January, I witnessed the death of a Golden Retriever with a malignant splenic tumour.

The spleen is a mysterious part of the anatomy to most people. We all have a spleen, animals and humans alike, but it isn’t something that we think about much. And, indeed, it can safely be ignored unless something goes wrong with it: it doesn’t play an obvious role in our day-to-day lives. In dogs and cats, the main reason to worry about the spleen is that it’s a common location for tumours to develop, especially in older pets.

In a healthy animal, the spleen has a number of important housekeeping functions, mostly involving blood cells. As well as storing up to 20% of the body’s red blood cells at any given time, the spleen produces various types of blood cells (both red and white), removes and processes ageing red blood cells, and it plays an important role in the immune system, helping to deal with antigens. However. it’s one of those organs that animals seem to be able to manage without (so it doesn’t create a big crisis if it’s removed for any reason).

It’s rare for spleens to cause problems in young animals, but tumours of the spleen are one of the most common types of cancers to affect older pets. The cause of splenic tumours remains unknown, although there’s a genetic element, with certain dog breeds being more commonly affected (e.g. German Shepherds, Golden Retrievers, Labradors and Boxers). In cats, a common virus (Feline leukaemia Virus, or FeLV) is sometimes involved.

Many cancers in other parts of the body cause problems because the abnormal cancer tissue disrupts the normal function of the organ (e.g. in liver or kidney cancer). When the spleen is the location of cancer, the effect on its function is not usually noticeable. Instead, one of two scenarios draws attention to the problem.

First, the sheer size of the cancer can cause a swollen abdomen, and the work of carrying the extra weight can cause affected animals to become dull and tired (a splenic mass can grow to the size of a football inside the abdomen of a large dog).

The second scenario happens when, as the tumour on the spleen grows, it eventually bursts, like an over-ripe tomato. When this happens, blood leaks into the abdomen, and this internal haemorrhage has the same impact on the animal as severe blood loss to the outside of the body. They develop severe anaemia, their gums turn pale, their heart races, and they often collapse. 

This is a serious crisis, and affected pets need to be rushed to the vet. The tumour is usually diagnosed by diagnostic imaging (either x-rays or ultrasound examinations), and once this has been identified, a decision has to be made on treatment.

The biggest challenge with splenic tumours is the fact that it is impossible to know what type of tumour is present without carrying out laboratory analysis of the tumour itself. We know that around one-third of tumours on the spleen are completely benign. In these cases, if the tumour can be successfully removed and the dog recovers, they will return completely to normal, and live the rest of their life as if nothing had happened.

In contrast, around two-thirds of tumours on the spleen are malignant. If these tumours are removed, again, once the dog survives the operation, they may seem to return to normal health at first, but it’s inevitable that the cancer will return. Most dogs with malignant splenic tumours live for less than six months after the operation.

This means that when a dog presents with a tumour on their spleen, owners need to make a difficult decision. 

All that we can tell them, as vets, is that there is a one-in-three chance of their dog making a full recovery, but a two-out-of-three chance of their pet only living for a few more months. 

It’s only after the spleen has been removed, then sent off to the laboratory for analysis, that a detailed prognosis can be given.

Whether the tumour is benign or malignant, the only possible way forwards is surgical removal of the spleen, including the tumour. This is a major operation: if you can imagine extricating a football with a rich blood supply from the depths of a dog’s abdomen, you’ll get the picture. It’s a time-consuming and expensive procedure, with a high risk of mortality during the operation, and an uncertain prognosis even if they pull through. 

Many dogs need intensive care, with blood transfusions and around-the-clock monitoring. Understandably, because of the questionable prognosis, and the high cost, some owners decide not to proceed with the operation, choosing euthanasia instead of putting their animal through such a major event.

There is no easy answer for this situation: it is impossible to accurately predict, at the time, whether a tumour on the spleen is benign or malignant.

The best approach, if possible, is just to do whatever is necessary to save the animal’s life by carrying out the operation and then sending off the tumour to have it analysed. After the dog, hopefully, recovers from the surgery, the uncertainty just has to be accepted for a week or so, until the results arrive from the laboratory.

This is a common problem: as a vet in a busy practice, I see cases like this around once a month. In January, I witnessed the death of a Golden Retriever with a malignant splenic tumour. Last week, a Spaniel had a splenic tumour, of almost an identical size and appearance, removed. The laboratory results have just come back: this one was benign, and the great news is that this much-loved pet will now go on to live a normal length of life.