Emergency en Bloc Resection of a Ruptured Hemangiosarcoma Anatomically Associated with the Right Retroperitoneal Space, Kidney, and Caudate Hepatic Lobe in a Dog.

A 13-year-old, spayed female Maltese dog presented with acute collapse and profound lethargy of approximately 1 h duration. On admission, the dog was in hypovolemic shock, with severe hypotension, marked pallor, tachycardia, and hemoperitoneum identified by focused abdominal ultrasonography. Ultrasonography also revealed a ruptured hemorrhagic mass in the right retroperitoneal space. Because the patient was hemodynamically unstable and ongoing life-threatening hemorrhage was suspected, preoperative computed tomography was considered unsafe, and emergency exploratory laparotomy was performed following transfusion-based resuscitative stabilization. Intraoperatively, the lesion was found to involve the right kidney and caudate hepatic lobe. En bloc resection, including right nephrectomy, partial hepatectomy, and excision of the retroperitoneal-associated mass, was completed while preserving the right adrenal gland and adjacent major vasculature. Histopathologic and immunohistochemical evaluation supported a diagnosis of solid-pattern hemangiosarcoma, although a single primary site of origin could not be definitively assigned. The dog recovered without major perioperative complications, was discharged in stable condition, and maintained good quality of life for approximately 1 year; however, late clinical decline suspicious for recurrence or progression was not objectively confirmed. This case highlights the practical utility of focused ultrasonography, rapid surgical decision-making, and carefully planned en bloc resection for emergency hemorrhage control in a dog when advanced imaging was considered unsafe.