April 12, 2023 Cats Dogs Internal Medicine

The Spleen: Do Dogs and Cats Really Need One?

Anatomy of a cat

The Spleen: Do Dogs and Cats Really Need One?

Through the centuries, medical practitioners have ascribed many functions to the spleen. In the Middle Ages, physicians thought the spleen produced black bile, the cause of melancholy. In later years, doctors believed the spleen served as a filter for the liver. Today, we know the spleen is an organ of the immune system. Removal of the spleen is a common surgical procedure in veterinary medicine (a “splenectomy”), and it is used to treat a number of diseases. In this blogpost, I’ll discuss the unique properties of the spleen in dogs and cats and when it may be necessary to remove it.

What is the Spleen?

The spleen is a dark red organ that resides in the abdomen and is loosely attached to the border of the stomach by a thin veil of tissue and blood vessels. In most pets, the spleen is about as long as their forearm. It functions to help the body fight off infections and removes aged, nonfunctioning red blood cells from circulation. Neither dogs nor cats suffer long-term effects from the lack of a spleen, which is different than in humans. Humans without a spleen need to take special precautions to protect themselves from a serious infection.

Splenic Torsion in Dogs

Due to the loose attachment of the spleen to the stomach in dogs, the spleen can sometimes twist around itself and block the blood flow to the organ. This requires an emergency splenectomy. The lack of blood supply makes the dog acutely ill and, on examination, the ER veterinarian will feel a very enlarged spleen. The cause of this disorder is unknown, but surgery is curative. The twisting of the stomach in bloat or gastric dilation/volvulus can also disrupt the blood supply to the spleen and necessitate a splenectomy.

Increased Osmotic Fragility of Erythrocytes in Cats

One of the normal functions of a spleen is to remove old red blood cells. In cats with an unusual and as of yet unexplained disease, red blood cells are cleared at a more rapid rate than normal, resulting in anemia and an enormously enlarged spleen. This disease is known as increased osmotic fragility of erythrocytes, and removal of the spleen benefits the cat by improving the anemia.

Splenic Tumors in Dogs and Cats

Because dogs and cats tolerate removal of their spleens so well, splenectomy is a common treatment for tumors of the spleen. In dogs, the most common tumor of the spleen is hemangiosarcoma. Hemangiosarcoma is a tumor found in dogs and cats, but not in people. This tumor bleeds easily, and the first sign of hemangiosarcoma is often collapse due to blood loss from the spleen. Emergency splenectomy stops the bleeding. The abdominal x-ray below is typical of a dog with a rare splenic tumor called hemophagocytic histiocytic sarcoma. The x-ray of a cat’s abdomen shows an enlarged spleen due to mast cell tumor, the most common spleen tumor in the cat.

X-ray of a dog with a rare splenic tumor called hemophagocytic histiocytic sarcoma
Abdominal x-ray of a dog with a splenic tumor called hemophagocytic histiocytic sarcoma.
X-ray of a cat’s abdomen shows an enlarged spleen due to mast cell tumor
Abdominal x-ray shows a cat’s enlarged spleen due to mast cell tumor.

In Summary: Yes, Dogs and Cats Can Live Without a Spleen!

Although none of us want our pet to have a serious disease requiring splenectomy, a splenectomy often results in a dramatic improvement in a pet’s quality of life without long-term negative consequences.

Tags: anemia, animal medicine, hemangiosarcoma, spleen, splenectomy, veterinary medicine,

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