Some weeks seem to have a medical theme. For me, this week’s theme is the spleen or, more accurately, the absence of one as I wrote earlier this week about the case of Walker. Many of my patients this week have had their spleen surgically removed, a procedure called a splenectomy.
The spleen is a dark red organ which 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 as part of the immune system, helping the body to fight off infections and removing aged, non-functioning 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.
Veterinarians don’t know the cause, but several different disorders affect the spleen and disturb its normal function. Some disorders require a splenectomy as part of the treatment.
The loose attachment of the spleen to the stomach can sometimes result in the need for an emergency splenectomy in a dog if the spleen twists around itself and blood flow to the organ is blocked. 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.
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. In this disease, known as increased osmotic fragility of erythrocytes, removal of the spleen benefits the cat by improving the anemia.
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.
The x-ray of a dog’s abdomen (shown below) is typical of a dog with a rare splenic tumor called hemophagocytic histocytic 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.
Although removal of an organ is medically serious, a splenectomy often results in a dramatic improvement in a pet’s quality of life without long-term negative consequences.
Outlined is a very large, but smooth spleen in a cat. This is due to a mast cell tumor.
Outlined is a very large, but irregular spleen in a dog. This is due to hemophagocytic histocytic sarcoma.