By Dr. Gail Mason, DVM, MA, DACVIM
Staff Internist, Portland Veterinary Emergency & Specialty Care
The spleen is an intraabdominal organ that is located just below the stomach. The spleen plays an important role in the immune system of the body while producing certain types of white blood cells that can clear infections. It also acts like a processing plant for red blood cells in that it removes old or defective red blood cells and can readily produce new ones. Unfortunately, the spleen is a common site for the development of tumors, especially in older dogs. Because the spleen stores and produces red blood cells, even benign tumors risk eventual rupture and acute hemorrhage. Breeds at higher risk include German shepherds, Golden retrievers, Labrador retrievers, boxers, standard poodles, Bernese Mountain dogs, and flat-coated retrievers.
Tumors of the spleen are classified as benign (noncancerous), malignant (cancerous), primary (originating in the spleen itself), or metastatic (spread from another site of cancer). Types of splenic malignancies Include lymphoma, mast cell disease, multiple myeloma, histiocytic sarcoma, leiomyosarcoma, carcinoma, and hemangiosarcoma.
How are they discovered?
The best-case scenario is when a splenic mass is suspected or detected upon physical examination by a veterinarian in a patient showing no symptoms. This emphasizes the importance of at least annual physical examinations for older animals and gives the owner the opportunity to collect more information in an organized way. However, palpation cannot distinguish a benign vs. a malignant tumor. Most frequently, an abdominal ultrasound is performed as the next diagnostic step. While no test is 100% accurate, a detailed ultrasound can give information as to whether or not the tumor is confined to the spleen and therefore may be removed. Additionally, the clinician may want to sample the mass (most frequently via a needle biopsy) to help determine diagnosis and prognosis. Sometimes, splenic masses are found on radiographs (X-rays) or ultrasounds as incidental findings.
What’s the emergency?
Unfortunately, because most splenic tumors do not cause the animal any pain, they are discovered only when they are large enough to rupture. This can happen with either benign or malignant tumors, and it constitutes a medical emergency. Rupture of the spleen can result in acute hemorrhage or loss of blood into the dog’s abdomen. This can be very sudden in nature and the most typical “shock” symptoms include acute collapse, pale to white gums, increased respiratory rate, increased heart rate, and distension of the abdomen. This is secondary to blood loss and a rapid drop in the dog’s blood pressure. Some dogs will have a minor hemorrhage and after a bit of rest, their blood pressure normalizes. While they may seem “normal”, there is an extremely high risk that a more serious hemorrhage will occur within a short time. This results in an extremely stressful situation for dog owners!
What to do?
If your dog should manifest any of these symptoms, seek emergency care at once as this scenario is truly life-threatening. The emergency doctor will likely do a quick assessment, treat the dog for shock, and do some preliminary screening blood work. Most emergency hospitals have access to ultrasound which can be crucial in decision-making. The doctor must determine if the tumor appears to be confined to the spleen, its general characteristics, and the nature of the fluid within the abdomen. Regardless of tumor size or type, some dogs require blood transfusions to stabilize their cardiovascular system. Though the exact diagnosis may not be known, if there is no direct evidence of metastatic disease in the abdomen or lungs, then surgical removal of the spleen is feasible. The surgery can certainly be lifesaving, and although all surgeries carry some risk, they are generally successful. Dogs can live fine without their spleens, and in a relatively stable patient hospitalization is only 1 or 2 days.
If the tumor is determined to be benign in nature, then surgery would be expected to be curative. Slow-growing malignancies can also result in a fair to a good prognosis. The overall odds, however, are against this scenario. Approximately 83% of all splenic tumors in dogs are malignant, with approximately 87% of those tumors resulting in a diagnosis of hemangiosarcoma (HSA).
This common splenic tumor has an extremely aggressive biological nature. Survival times for dogs with HSA after splenectomy alone, range from only 1 to 2 months. There are treatments that include chemotherapy and targeted drugs for this disease which can extend excellent quality of life for approximately 6 to 8 months. The diagnosis and treatment of splenic malignancies are highly active areas of research. There are currently several screening blood tests for malignancies called “liquid biopsies,” which are noninvasive and improving in accuracy. This is a good time to make an appointment for your senior dog’s annual or semi-annual physical examination!