Imaging diagnosis: Disseminated hemangiosarcoma in a Welsh pony.

Imaging techniques, particularly contrast-enhanced CT scans, were used to diagnose disseminated hemangiosarcoma in a Welsh pony presenting with epistaxis and neurological signs. Postmortem examination confirmed widespread hemangiosarcoma affecting the sinonasal region, brain, cervical vertebra, and multiple thoracoabdominal sites.

Case Presentation and Initial Diagnosis

• A 16-year-old Welsh pony gelding showed symptoms of epistaxis (nosebleed) and a head tilt.
• Initial skull radiographs suggested the presence of an ethmoid hematoma, a benign mass in the sinus region.
• Neurologic abnormalities alongside these findings prompted further diagnostic imaging.

Advanced Imaging and Findings

• A contrast-enhanced computed tomography (CT) scan was performed on the head and cranial neck.
• The CT scan revealed multiple hyperattenuating (high-density) masses in the brain and paranasal sinuses.
• A large osteolytic (bone-destroying) mass was identified in the second cervical vertebra, extending into the vertebral canal.
• This vertebral lesion caused focal extradural compressive myelopathy, meaning compression of the spinal cord outside the dura mater leading to neurological impairment.
• These CT findings did not match those expected from an ethmoid hematoma.

Differential Diagnosis and Clinical Considerations

• Because of the CT findings, metastatic hemangiosarcoma or malignant melanoma were considered likely causes rather than ethmoid hematoma.
• Hemangiosarcoma is a malignant tumor arising from blood vessel cells that can spread (disseminate) widely.
• This malignancy can cause multiple masses in various tissues including bone, brain, and sinonasal regions, correlating with the pony’s clinical signs.

Postmortem Examination and Final Diagnosis

• Postmortem (necropsy) examination confirmed that the masses in the sinonasal region, intracranial space, and vertebra were hemangiosarcoma.
• Additionally, numerous metastatic lesions were found throughout the thorax and abdomen, along with areas of hemorrhage.
• The diagnosis was disseminated hemangiosarcoma, indicating widespread metastatic disease.

Significance of Imaging in Diagnosis and Management

• Contrast-enhanced CT was crucial for accurately assessing the extent and nature of the lesions.
• The imaging revealed the regional involvement of neural structures, such as the brain and spinal cord.
• This detailed characterization of disease severity and spread influenced clinical management decisions for the pony.
• The study highlights the importance of advanced imaging techniques in differentiating between similar presenting conditions and guiding diagnosis in equine patients.