Canine calvarial subperiosteal hematomas are fluid to soft tissue attenuating mass-like lesions with smoothly marginated peripheral mineralization on CT.

Subperiosteal hematomas are accumulations of blood between a bone and the periosteum leading to elevation of the periosteum. When ossified they have a mineralized outer rim. For this retrospective, multi-institutional case series, medical records were searched to identify dogs that underwent CT for focal calvarial swellings noted acutely after trauma. A total of four dogs were included. Computed tomography images were reviewed for each case. The focal swellings had progressed in size during the weeks after the head trauma until the time of imaging. Findings in all cases included a fluid to soft tissue attenuating mass-like lesion with smoothly marginated peripheral mineralization. Diagnosis was confirmed in two cases by cytology and/or histopathology. Therefore, authors recommend that subperiosteal hematoma be included in the differential diagnosis list for dogs with these clinical and CT characteristics. Based on our review of the literature, this is the first report to describe the CT features of calvarial subperiosteal hematomas in dogs.