Understanding Splenomegaly in Dogs: Common Causes & Diagnosis
- Dr. Zeke Zekoff
- Apr 23
- 2 min read
The spleen is a vital organ responsible for filtering blood, supporting immune function, and storing red blood cells and platelets. When it becomes enlarged—known as splenomegaly—dogs may experience symptoms ranging from mild discomfort to life-threatening conditions like hemoabdomen. Identifying the cause of splenomegaly is crucial for determining appropriate treatment.
Top 5 Causes of Splenomegaly in Dogs
Hemangiosarcoma – The most common splenic malignancy, hemangiosarcoma arises from the vascular endothelium, often leading to large cavitary masses. It frequently affects older, larger breeds and can cause anemia, hypovolemia, and collapse due to internal bleeding. Diagnosis involves imaging, blood tests, and histopathology. Prognosis is generally poor, but surgical removal followed by chemotherapy can extend survival.
Extramedullary Hematopoiesis (EMH) – This occurs when blood cell production takes place outside the bone marrow, typically in response to an underlying hematologic disorder. It causes diffuse splenic enlargement and is associated with conditions such as immune-mediated hemolytic anemia. Diagnosis is made through fine-needle aspiration and blood work.
Multicentric Lymphoma – Lymphoma is a systemic cancer that often infiltrates the spleen, creating a distinct “honeycomb” pattern seen on ultrasound. Diagnosis can be confirmed with cytology or flow cytometry. Chemotherapy remains the primary treatment, leading to high remission rates and extended survival.
Nodular Hyperplasia & Hematoma – These benign lesions develop from hyperplastic nodules and may result in hemorrhaging. They appear as focal or diffuse masses in imaging but cannot be distinguished from malignant tumors without histopathology. While typically non-cancerous, they can cause hemoabdomen and require surgical removal.
Congestion – Conditions such as sedation, anesthesia, heart failure, thrombosis, or portal hypertension can lead to splenic congestion. This can result in severe enlargement, as the spleen stores significant amounts of blood. Treating the underlying disorder can often resolve splenomegaly, but surgical removal may be necessary in cases of splenic torsion.
Diagnosis & Treatment
Dogs with splenomegaly often present with lethargy, vomiting, abdominal enlargement, and, in severe cases, shock. Diagnosis involves physical exams, imaging (ultrasound, X-rays), and fine-needle aspiration or biopsy. Understanding whether the condition is benign or malignant is critical, as treatment options range from medical management to surgical intervention.
While splenic enlargement can be alarming, early detection and proper veterinary care can improve outcomes. Pet owners should seek immediate veterinary attention if their dog exhibits symptoms of splenomegaly.
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