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What Is The Spleen?

Written by Staff Veterinarian

What is the spleen?

The spleen is a tongue shaped organ of the abdomen that acts as a reservoir for blood as well as filters the circulating blood. It removes and recycles old red blood cells and attacks any blood borne pathogens like bacteria and parasites commonly associated with tick borne diseases via its large volume of lymphoid tissue (immune system).

Canine and feline spleens may distend and contract to help increase circulating blood volume and this can be influenced by anesthetic medications. Spleens can be surgically removed without significant compromise to our pets’ long term health.

When does an enlarged spleen need to be further evaluated?

Patients may be presented to a veterinarian for a variety of non-specific signs of illness resulting from an enlarged spleen or splenic mass. Vomiting, inappetence, weight loss, low energy, pale mucus membranes (gums), or simply enlargement of their abdomen can be symptoms that a pet exhibits when there is a problem with their spleen. A veterinarian may incidentally find a mass when palpating the abdomen on yearly health exams. Splenic masses can be caused by a variety of diseases ranging from infection (abscess) to a tumor (benign vs. malignant), which is more common. Additionally, systemic diseases or malpositioning of the spleen may also increase its overall size. Diagnostic tools veterinarians have to differentiate these multitude of diseases are x-rays (radiographs), abdominal ultrasound, CT (computed topography), and sometimes MRI (magnetic resonance imaging).

Radiographs give an excellent over-view of a patient’s abdomen and help to appreciate the overall size and shape of organs in comparison to the rest of the patients’ abdominal organs. Abdominal ultrasound is superior at looking at the inside architecture of abdominal organs and can determine different characteristics of the enlarged spleen or splenic mass that help guide treatment recommendations and provide tentative prognoses.

The abdominal ultrasound can determine the location of a mass and whether it is associated with the spleen. Unfortunately, tumors of the spleen are reported to be a malignant cancer more often than not. Because tumors of the spleen typically arise from the blood vessels (hemangiosarcoma), the spread or metastasis of the tumor has already occurred at time of diagnosis and or the tumors have ruptured and are actively bleeding into the patients’ abdominal cavity. The liver is commonly affected with metastasis of splenic cancers, so evaluation with an abdominal ultrasound can help determine if this is apparent. Additionally, bleeding into the abdomen from the spleen can be assessed and diagnosed via abdominal ultrasound.

What are common tumors of the spleen?

The most common splenic tumor is the malignant cancer, hemangiosarcoma. This is a tumor of the blood vessels and as a result can easily rupture and cause life threatening bleeding. Unfortunately, diagnosis of a hemangiosarcoma requires tissue analysis (histopathology), which is typically completed with surgical removal of the spleen, and stops the active bleeding. There are less concerning tumors of the spleen that can also rupture (hemangioma, hematomas) that once removed surgically are curative and should not affect your pet’s long term survival. Other tumors include different sarcomas, lymphoma, and mast cell tumors (more commonly in cats). Non-tumor diseases like infection (abscess) and splenic torsion (strangulation of splenic blood vessels), are also causes of an enlarged spleen, necessitating surgery.

What does surgery entail for your pet if they have been diagnosed with a splenic tumor or general enlargement of the spleen?

Canine and feline patients will be assessed thoroughly by a veterinarian to ensure they are stable and safe to proceed with surgery. This typically entails complete blood work, chest x-rays, and blood type check to ensure that if a blood transfusion is needed the hospital is prepared.  Your family member will be put under general anesthesia and will have their abdomen clipped of hair for sterility purposes. Through a long incision, the entire abdomen and abdominal organs will be thoroughly evaluated for abnormal changes. Samples of other organs will be safely obtained if deemed necessary. The spleen will then be isolated and removed. Often using special vessel sealing and incising devices, LigaSure, adopted from human surgeons, will be used to safely and quickly remove the spleen stopping any current bleeding and obtaining the necessary tissue for analysis (histopathology).

How long does my pet need to recover from surgery?

Following their successful recovery from anesthesia, your pet will need to be in the hospital for a couple of days for close monitoring. Blood transfusions can be common for patients that were bleeding from their masses before surgery. Bleeding after surgery is unlikely, but possible, and this will be closely monitored. Heart arrhythmias (irregular heart rhythm and activity) can be present that may need to be treated with medications. As your pet improves, they will be transitioned to oral medications and prepared to discharge home for further recovery. Typically patients need 2 weeks of strict exercise restriction and rest. Monitoring their incision for signs of infection and supportive care with medications are the mainstay of their at home recovery. After 2 weeks of a successful recovery, they are allowed to go back to normal activity.

If my pet is diagnosed with hemangiosarcoma, what is their prognosis?

Unfortunately, hemangiosarcoma is a very serious and debilitating cancer. The average patient following a diagnosis of splenic hemangiosarcoma will only have a life expectancy of around 3 months. Chemotherapy may extend survival with hemangiosarcoma and we advise meeting with one of our oncologists after a diagnosis of hemangiosarcoma to see if further treatment would be appropriate for you and your pet. Chemotherapy is well tolerated in our canine and feline patients. They receive intermittent injections or pills on an outpatient basis and only a small percentage (less than 15% will experience nausea, vomiting, or low white blood cells requiring antibiotics. There are ongoing studies and trials occurring nationwide trying to find drugs that could improve survival following a diagnosis of hemangiosarcoma.