A prospective observational study of 345 canines with ruptured splenic tumors suggests benign lesions are more common than previously reported.

Objective: To define the histopathologic diagnoses and clinical stage from a prospectively enrolled cohort of dogs with spontaneous hemoperitoneum (SH) of splenic origin undergoing splenectomy.

Methods: This post hoc analysis of prospective data evaluated canine patients presenting with SH enrolled into a nationwide study of ruptured splenic tumors undergoing splenectomy from October 2020 to June 2024.

Results: This study enrolled 345 dogs with SH secondary to a ruptured splenic tumor. Benign lesions accounted for 35.7% of all dogs (n = 123), and malignant tumors accounted for 64.3% of all dogs (222). Of the malignant tumors, hemangiosarcoma (HSA) represented 56.2% of all dogs (n = 194) and other malignant tumors represented 8.1% of dogs (28). The median weight in kilograms and age in years for all dogs enrolled were 27.9 kg (5.4 to 84.5 kg) and 10 years (3 to 15 years), respectively.

Conclusions: While splenic HSA (spHSA) has remained the most common cause of SH in canines, benign lesions had a higher prevalence in this study at 35.7% (n = 123) than previously reported. There was no statistically significant difference identified when comparing body weight or age between the groups.

Clinical relevance: This study did not identify a statistically significant correlation between age or weight with the development of spHSA and reported an overall higher incidence of benign lesions, thus calling for an adjustment to the narrative claiming that old large-breed dogs have a higher prevalence of spHSA. The published data represent the largest prospective study on SH of splenic origin in canines and can be utilized by the practicing clinician to provide a comprehensive discussion when recommending surgical intervention.