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Overview
Dogs may develop masses in their spleens. These masses can be benign or malignant, but because they are blood-filled, life-threatening bleeding can occur if they rupture. Surgical removal is usually recommended to find out the exact cause of the mass and to prevent or stop bleeding.
Causes
Most splenic nodules are benign hyperplastic lymphoid nodules and/or hematomas. Some nodules are malignant tumors. Half of the tumors in the spleen are hemangiosarcomas, which are blood-filled malignant tumors of the spleen that rapidly spread to other organs. The rest are a variety of tumor types, with varying degrees of malignancy.
Incidence and Prevalence
Splenic lesions (masses and other diseases) represented 1.3% of the specimens submitted to a large pathologic laboratory over a 50 month period. In a study of 500 dog spleens submitted for examination, 50% had cancer, while 50% had diseases other than cancer. Half of the dogs with cancer had hemangiosarcoma, while half had other tumors. Thus the odds that the cancer is hemangisarcomic are 50:50 and the odds that a splenic mass in a dog is hemangisarcomic are roughly 1:4. However, if the dog has splenic rupture and life-threatening abdominal hemorrhage, the chances that the dog has hemangiosarcoma increase, with approximately 70% having hemangiosarcoma.
Signs and Symptoms
Dogs with splenic masses frequently show no signs of disease. They may develop vague weakness or lethargy if they become anemic. If the mass becomes large, dogs may have some difficulty breathing or sleeping comfortably. If large, the mass may be able to be seen or felt. If the mass ruptures, the dog usually collapses and becomes pale and weak, or if the blood loss is severe, death may occur rapidly.
Risk Factors
Older, large breed dogs are at increased risk of having a splenic mass. German Shepherd Dogs, Golden Retrievers and Labrador Retrievers are most commonly affected.
When to Seek Veterinary Surgical Advice
If your dog collapses due to bleeding into the abdomen, this is a surgical emergency. Transfusion is often needed, the bleeding must be controlled and the spleen should be removed as soon as possible. If a splenic mass is found on radiographs or ultrasound, but your animal is not bleeding, you should discuss removal of the spleen with your veterinarian. Your regular veterinarian may perform this surgery, or may wish to refer you to a surgical specialist. To find an ACVS veterinary surgeon in your area, click here: Find a Surgeon.
Exam, Screening Tests and Imaging
If your dog collapses and bleeding into the abdomen is suspected, a sample of abdominal fluid will be obtained to confirm the hemorrhage. Ultrasound may be used to confirm that blood is present in the abdomen and to see the extent of the splenic mass, but in very critical cases your dog may be rushed to surgery to stop the bleeding without imaging. For less critical cases, radiographs or ultrasound are used to image splenic masses. If a mass is felt on a physical exam or if a blood test shows that your dog is anemic or has abnormal red blood cells, your veterinarian may suggest that the spleen be imaged.
Differential Diagnosis
It is not usually possible to determine what type of splenic mass is present without examining it carefully under the microscope (histopathology). Some masses are easily determined to be benign or malignant, but there are a number of splenic nodules that have some, but not all, the characteristics of malignancy. The pathologist will grade these tumors and the animal's prognosis will depend on the grade. Splenic nodules with a high ratio of histiocytes to lymphocytes (two cell types) or a high mitotic index have a poorer prognosis. Mitotic index is a measure of the growth rate of the tumor. A high mitotic index indicates that the tumor is rapidly dividing.
Complications Caused by the Disease
Abdominal bleeding due to rupture of the mass is the major complication.
Treatment Options
Partial or complete removal of the spleen is the main treatment for splenic masses. (Figures 1 and 2). Most owners choose to have the spleen removed once they know a mass is present, because there is the potential for a benign mass to become malignant over time. Owners of dogs with no clinical signs and small splenic masses that appear benign on a needle aspirate may elect not to have surgery performed. The mass should be followed over time with an ultrasound exam. If the mass becomes larger or clinical signs develop, it should be removed.
Figure 1. A splenic mass at the time of surgery. The spleen has been removed from the abdomen and the surgeon's hand is on the mass. The normal portion of the spleen is to the right of the large mass.
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Figure 2. A spleen with a large splenic mass following complete removal of the spleen at surgery.
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Potential Complications Following Surgery
In the immediate post-operative period, heart rhythm abnormalities may develop. Post-operative bleeding may occur. Removal of the spleen may make the dog more susceptible to certain blood parasites such as Ehrlichia canis.
Aftercare
Many large vessels are ligated during splenectomy. There is a long abdominal incision. The dog must be kept quiet for 10-14 days after surgery to prevent bleeding or incisional problems. If your dog starts licking at the incision, a body sock or head collar may be recommended.
Prognosis
The prognosis for dogs with benign hyperplastic nodule/hematoma lesions is excellent. The prognosis for dogs with lymphocytic/histiocytic nodules depends on exact cell mixture in the mass and the mitotic index of the mass, with survival ranging from 0-15 months. The prognosis for dogs with splenic sarcomas other than hemangiosarcoma depends on the mitotic index. Median survival time for dogs with hemangiosarcoma treated with splenectomy is 3-4 months. Dogs treated with splenectomy and chemotherapy have a median survival time of 6-8 months.
Prevention
There is no known prevention for the development of splenic masses.
—Elizabeth Hardie, DVM, PhD
Diplomate ACVS
Posted 8/13/2004
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