Patient X, a male, castrated, mixed breed dog, presumed to be approximately 3 years old, presented to Cornell University's CPS for evaluation of a rectal mass. Two days prior to presentation, the owner had noted that X had dyschezia, along with runny dark colored stool, and upon closer examination found the rectal mass. At the time of initial presentation a rectal exam was unable to be performed due to the patient's level of discomfort, however, abdominal palpation revealed a soft tissue mass in the caudal left abdomen that was independent of the bladder. An abdominal ultrasound was performed and disclosed an 8 x 4 x 5 cm heterogeneous mass occupying a large portion of the pelvic inlet. The left iliac artery and immediate downstream arterial branches were closely associated with the dorsal aspect of the mass. The mass was not directly associated with other caudal abdominal or pelvic viscera. Complete blood count and serum chemistry were found to be unremarkable. Surgical consultation was sought following which it was decided that X would undergo general anesthesia and ultrasound guided fine needle aspiration for cytological characterization of the mass. Cytology was inconclusive and surgical exploration of the caudal abdomen and mass excision was undertaken which ultimately required ligation and excision of the left iliac vessels. This case report reviews the regional anatomy of the caudal abdominal vasculature and autonomic nervous system and discusses potential devastating consequences of extensive caudal abdominal dissection and vascular occlusion.