A 3 year old male intact Greater Swiss Mountain dog presented to the Emergency Service at Cornell on 3/16/09 with lethargy, abdominal distension, and pale mucous membranes. Two weeks prior to presentation, patient was witnessed having several seizures and was started on phenobarbital by his regular vet without further incident. The following week, the patient's abdomen was noticed to be distended and he was lethargic. He did not improve and on 3/15, the owners noticed he was very lethargic and his gums were pale. He was stabilized and referred to Cornell University Hospital for Animals Emergency and Critical Care Service for further work up. Upon arriveal at Cornell, there was a large mass effect palpated on the ventral abdomen extending up the abdominal wall. An abdominal ultrasound revealed splenic infarction and necrosis. Findings were consistent with a splenic torsion, though the torsion could not be visualized. An abdominal exploratory was performed. Under general anesthesia, the patient developed a ventricular tachycardia and runs of premature ventricular complexes. A splenic torsion and a very large, necrotic spleen were found at surgery. The thrombosed vessels and spleen were resected at the level of the torsion. The arrhythmia resolved and a prophylactic gastropexy and castration were performed simultaneously. This report will discuss clinical and diagnostic signs associated with splenic torsion, differential diagnoses to rule out, and prognosis. Speculative causes for splenic torsion will be discussed, though the exact etiology is unknown.