Diagnosis, Perioperative Management, and Surgical Treatment of Suspected Functional Pheochromocytoma in Two Dogs: Surgical Complexity in the Absence of Planned Venotomy.

Functional pheochromocytoma is an uncommon canine adrenal tumor associated with substantial surgical and anesthetic challenges. This report describes two dogs with suspected functional pheochromocytoma that exhibited distinct causes of surgical complexity. Both underwent endocrine evaluation, contrast-enhanced CT, adrenalectomy, and histopathology. In Case 1, severe perivascular adhesion resulted in an iatrogenic caudal vena cava laceration despite the absence of definitive vascular invasion, requiring primary venorrhaphy. In Case 2, marked tumor-induced vascular distortion obscured critical anatomical landmarks, necessitating staged surgical management. Three-dimensional vascular reconstruction facilitated refinement of the surgical approach, while individualized anesthetic management enabled successful surgery despite marked intraoperative hemodynamic fluctuations. Histopathology confirmed pheochromocytoma in both dogs, including malignant pheochromocytoma in Case 2. Case 1 developed chronic kidney disease during long-term follow-up, whereas no clinical evidence of local recurrence or distant metastasis was observed during the available follow-up. These cases demonstrate that surgical complexity may arise from severe perivascular adhesion and tumor-induced vascular distortion, even without planned vascular lumen entry or advanced vascular procedures. Patient-specific anatomical assessment, individualized perioperative planning, and selective 3D vascular reconstruction may improve surgical safety in complex adrenal tumors.