Clinical features and imaging characteristics of penile hematoma mimicking priapism in a dog

A 2-year-old, castrated male Jindo dog presented with 6 days of penile swelling and protrusion, suggesting priapism. Blood gas was analyzed by aspirating the corpus cavernosum to differentiate the type. However, the results were ambiguous. Ultrasound and computed tomography revealed a well-encapsulated mass ventral to the urethra. Magnetic resonance imaging showed a mass (T2-hyperintense, T1-hypointense, with no contrast enhancement) located ventral to the urethra. Cytology revealed only red blood cells, confirming a hematoma. Penile hematoma mimicking priapism was diagnosed. After 11 weeks of glucocorticoid administration, the hematoma and the protruded penis resolved. This case suggests that penile hematoma can be confused with priapism in dogs. MRI can be useful for evaluating penile membranous structures in dogs with swollen penises.