Updated September 25, 2026. Fact-checked against veterinary sources; review by a licensed veterinarian is in progress. See our editorial policy.
Quick answer: An enlarged spleen in cats is often found by a vet feeling the belly or on imaging. Common causes include mast cell tumors (the most common splenic cancer in cats), lymphoma, infections, immune-related anemia, and the spleen making extra blood cells. Signs may be vague, such as vomiting, poor appetite, and weight loss. Many cats with splenic mast cell tumors do well after the spleen is removed.
Signs
- Vomiting
- Poor appetite and weight loss
- Lethargy
- A swollen belly
- Pale gums if anemia is present
Causes
- Mast cell tumors
- Lymphoma
- Infections, such as blood parasites or FIP
- Immune-mediated anemia
- Extramedullary hematopoiesis (the spleen making blood cells)
Diagnosis
- Bloodwork
- Abdominal ultrasound
- Fine needle aspirate of the spleen
- Tests for infectious disease
Treatment
- Splenectomy for mast cell tumors, often with good outcomes
- Chemotherapy for lymphoma
- Treatment of infections or immune disease
- Antihistamines and stomach protectants for mast cell disease
Sources
- Merck Veterinary Manual: Mast cell tumors
- Merck Veterinary Manual: Lymphoma in cats
- Evans BJ, et al. Treatment outcomes and prognostic factors of feline splenic mast cell tumors: a multi-institutional retrospective study of 64 cases. Vet Comp Oncol. 2018
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