Splenic Mass Assessment (Double Two-Thirds Rule)
Clinical judgment required. This calculator is a decision-support tool, not a substitute for veterinary consultation.
Splenic Mass Assessment (Double Two-Thirds Rule)Canine
Estimate probability of malignancy for splenic masses in dogs using the double two-thirds rule and clinical modifiers. Approximately 2/3 of splenic masses in dogs are malignant, and of those, 2/3 are hemangiosarcoma (HSA). Adjusts probability based on presence of hemoabdomen, thrombocytopenia, and mass characteristics. Based on published retrospective studies. Used for surgical decision-making, prognosis discussions, splenic tumor evaluation, and pre-operative counseling for splenectomy in dogs.
Is there free abdominal fluid consistent with hemorrhage?
Platelet count below reference range?
Evidence of mass rupture on imaging?
Estimated Benign Probability
33.3%
Estimated HSA Probability
44.5%
Estimated Malignancy Probability
66.7%
66.7 %
50 %
75 %
Moderate
High
High
High—66.7 %
Moderate-high risk of malignancy — discuss prognosis and staging