Just like every other bronchial pattern....

Veterinary Radiology & Ultrasound, 2020.

Author

Obi Veterinary Education
September 08, 2025

Ashley L. Melco, Nicholas P. Petrovitch, Adam J. Birkenheuer, Tzushan S. Yang, Megan E. Schreeg, Mason Savage.

Background
Cytauxzoon felis is a tick-borne protozoan parasite that causes severe and often fatal disease in domestic cats. Histopathologic studies have documented significant pulmonary involvement in cytauxzoonosis, but there is little information on thoracic radiographic findings in affected cats. This study aimed to describe radiographic abnormalities in cats with confirmed acute cytauxzoonosis and evaluate their correlation with histopathologic lung lesions.

Methods
This retrospective study reviewed thoracic radiographs of 37 cats diagnosed with acute cytauxzoonosis based on blood smear or histopathologic findings. Radiographs were evaluated for pulmonary patterns, pleural effusion, pulmonary vascular distension, and cardiomegaly. A subset of seven cats underwent postmortem histopathologic lung evaluation to assess vascular and parenchymal changes.

Results
Radiographs revealed bronchial patterns in 73% of cats, interstitial patterns in 46%, and alveolar patterns in 24%. Pulmonary vascular distension was observed in 57%, and cardiomegaly in 51%. Pleural effusion was present in 32% of cases. Histopathologic evaluation confirmed vascular occlusion and interstitial pneumonia, but these findings were not consistently evident on radiographs. Despite severe histologic lung pathology, no single radiographic pattern was pathognomonic for cytauxzoonosis.

Limitations
This study was limited by its retrospective nature, small sample size for histopathologic evaluation, and lack of standardized imaging protocols. Additionally, some cats may have had concurrent respiratory conditions, confounding radiographic interpretation.

Conclusions
Thoracic radiographs in cats with acute cytauxzoonosis show variable pulmonary patterns but lack specific pathognomonic findings. Despite significant pulmonary pathology on histology, radiographic changes were inconsistent. Clinicians should consider cytauxzoonosis as a differential diagnosis for febrile cats in endemic areas with nonspecific respiratory abnormalities. Alternative imaging modalities, such as point-of-care ultrasound, may provide additional diagnostic value while minimizing stress in critically ill patients.

Left lateral thoracic radiograph. The most prominent intrathoracic features include a generalized bronchial and interstitial pulmonary pattern, arterial distention and cardiomegaly (VHS 8.55). Digital radiography images were obtained with Canon CXDI-50G Digital Flat Panel using CCR Software Version 81103, Canon Medical Systems Tustin, CA, USA; technique ranges were between 78–85 kVp and 2–2.5 mAs without a grid. For larger patients a 103 lines per inch grid with a ratio of 10:1 was used and techniques ranged from 87–95 kVp and 2.5–2.8 mAs

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