What are the indications for splenectomy in dogs and how does splenic mass histology affect prognosis?

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Splenectomy is indicated in dogs for splenic masses, torsion, trauma, immune-mediated hemolytic anemia, immune-mediated thrombocytopenia, generalized or localized splenomegaly, and splenic infarction. 111 Splenic masses are the most common surgical disease of the spleen, and histopathologic diagnosis after splenectomy is the primary determinant of long-term prognosis. 7 The malignant-to-benign ratio of splenic masses depends heavily on whether hemoperitoneum is present. In dogs presenting with nontraumatic hemoperitoneum, 73% of masses are malignant and 87% of those malignancies are hemangiosarcoma (HSA). 9 In dogs without hemoperitoneum, 70% of splenic masses are benign. 9 Across all dogs undergoing splenectomy for a splenic mass regardless of hemoperitoneum status, 52.9% have malignant disease and 46.8% have benign disease. 10 Small-breed dogs are 2.3 times more likely than large-breed dogs to have benign disease, and when small-breed dogs do have malignant disease, they are one-third as likely as large-breed dogs to have HSA. 14 HSA carries the worst prognosis of all splenic malignancies. Median survival time after splenectomy alone ranges from 19 to 132 days, extending to 144 to 277 days with adjuvant chemotherapy. 4 The 1-year survival rate is 6% to 12% with splenectomy alone and 8% to 23% with splenectomy followed by chemotherapy. 4 HSA has a metastatic rate of approximately 50% to 80%, with concurrent hepatic metastasis in 50% to 67% of cases. 7 Splenic spindle cell sarcomas (fibrosarcoma, myxosarcoma, leiomyosarcoma, liposarcoma, and undifferentiated stromal sarcoma) carry a median survival time of 1 to 9 months, with 59.4% of dogs succumbing to metastatic disease within 12 months of diagnosis. 4 Pleomorphic stromal cell sarcomas have reported survival times following splenectomy ranging from 16 to 650 days. 5 Localized splenic histiocytic sarcoma (HS) has a substantially better prognosis than disseminated HS. Dogs with localized splenic HS treated with sple