By Dr. Laura Hady
The spleen’s vital functions of storing blood, filtering pathogens, removing old blood cells and storing platelets often go unnoticed. In humans, the fist-sized spleen is on the left side of the abdomen. In dogs and cats, the spleen is flatter, has a tongue shape and extends from the left to right side of the abdomen. The following are bits of information about the spleen and health issues that may arise as our pets age.
- When your pet’s body is under severe stress, during strenuous exercise, or experiencing low oxygen (think trauma), the spleen can contract to release a high percentage of red blood cells into circulation that help bring oxygen to tissues and platelets, which are cells that help clot blood. On a day-to-day basis, the spleen produces white blood cells that help fight infections by destroying and removing bacteria and viruses. Finally, the spleen removes old and non-functional red blood cells from circulation.
- In deep-chested, large breed dogs, the stomach can become distended with gas and then twist on itself, a condition known as gastric dilatation-volvulus. When this happens, the spleen, which is attached to the stomach by a ligament, may also twist around the curtain of mesenteric tissue (volvulus), which holds the organs in place. The result is a cut-off of blood flow to the spleen, resulting in congestion and damage. In this case, the spleen will need to be carefully removed so as not to release blood clots into the circulation. Despite animals’ ability to live without a spleen, the stomach will need to be surgically attached to the abdominal wall because it can bloat and twist again due to the extra space left when the spleen is removed.
- Blood pockets (hematomas) and nodules on the spleen are common, age-related and non-cancerous. According to the American College of Veterinary surgeons, these hematomas and nodules account for 20%-41% of all splenic lesions. About 78% of pets live longer than two years after surgical removal. It may be advised that owners of older pets request a screening ultrasound scan of their pet’s abdomen to check for abnormal masses.
- Hemangiosarcoma is the most common malignant (harmful) tumor of the spleen in a dog, while lymphomas are the most common in cats. Hemangiosarcomas arise from the cells that line blood vessels, so they can also form in the heart, skin and muscle, and can quickly spread (metastasize) to the liver. Mild signs of hemangiosarcomas include decreased energy and appetite as well as weakness. However, most dogs with splenic or heart-based hemangiosarcomas often collapse, have an increased breathing rate or difficulty breathing, pale gums due to internal bleeding and even sudden death. If you have to bring your animal to a veterinarian, they will recommend stabilizing the animal, surgically removing the spleen, and send it off to determine if it is benign or malignant. The vet may also provide a referral for chemotherapy. Surgery and chemotherapy may extend your pet’s life for about a year, but there is often aggressive microscopic disease that may be elsewhere in the body.
While there is no way to prevent splenic cancer in pets, newer blood tests (liquid biopsy) can detect the DNA fragments of the tumor in the bloodstream. A liquid biopsy helps early detection, is less invasive than other biopsies and can help direct therapy.
Vivesto is a company that is enrolling pets in the Paccal Vet Hemangiosarcoma trial, based on a drug used in human medicine and with no cost to the pet owner. It also does not include a placebo group so that all participatingdogs receive active treatment. Other research trials involve stimulating the immune system via a vaccine, using older drugs such as rapamycin in combination with newer drugs, and exploring the role of herbs as adjunctive treatment for this devastating disease.
I am excited for these research advances because I lost my dog Sprite to hemangiosarcoma when it spread from his heart to his spleen. I would love to see other pet owners have better outcomes for their beloved cats and dogs.
