Incidental findings are common on thoracic CT of older cats

Journal of Small Animal Practice, 2016

Author

Obi Veterinary Education
August 22, 2025

C. R. Lamb, I. D. Jones

Background
Thoracic computed tomography (CT) is increasingly used in feline medicine for detecting respiratory diseases. However, many abnormalities detected on CT scans may be incidental or subclinical. This study aimed to assess the prevalence of subclinical thoracic abnormalities in cats and examine associations between CT findings and respiratory signs.

Methods
A retrospective review was conducted on 352 cats that underwent thoracic CT scans at a veterinary referral hospital. Signalment, clinical signs, and indications for CT were recorded. CT abnormalities were categorized into pulmonary collapse, bronchial disease, space-occupying lesions, pulmonary nodules, and other findings. Multivariable regression analysis was used to determine associations between respiratory signs and CT findings.

Results
Thoracic abnormalities were identified in 77% of asymptomatic cats, with pulmonary atelectasis (41%) and bronchial disease (24%) being the most common. Among cats with respiratory signs, dyspnea was significantly associated with space-occupying lesions, pulmonary consolidation, and atelectasis. Cough and tachypnea were also linked to space-occupying lesions. Older cats were more likely to show CT evidence of bronchial disease, and higher body weight was associated with pulmonary atelectasis. Despite significant associations, many abnormal findings occurred in cats without respiratory symptoms, complicating clinical interpretation.

Limitations
This was a retrospective study with inherent limitations, including variability in CT interpretation and lack of histopathologic confirmation of findings. Many cats had incidental CT abnormalities, raising concerns about overdiagnosis. The study did not assess the severity of detected lesions or their progression over time.

Conclusions
CT scans frequently reveal thoracic abnormalities in cats, including those without respiratory signs. While certain findings correlate with clinical signs, the high prevalence of incidental abnormalities complicates diagnosis. Careful clinical correlation is needed to avoid overdiagnosis and unnecessary treatments. Future studies should explore the clinical relevance of subclinical CT findings and their long-term impact on feline health.

Examples of CT images reported as showing signs of pulmonary atelectasis. All are transverse images displayed with window 1500 HU and centre −500 HU. (A) Sublobar atelectasis affecting the tip of the right cranial lobe (arrowheads) in a cat with chronic cough. There is mediastinal shift to the right. Other images showed signs of bronchial disease. (B) Bronchocentric atelectasis affecting the left cranial lobe (arrowhead) in a cat with metastatic adenocarcinoma and no history of respiratory signs. (C) Lobar atelectasis affecting the right middle lobe (between arrowheads) in a cat with chronic cough. The heart (H) is displaced to the right. Other images showed signs of bronchial disease. (D) Unilateral left lung atelectasis (*) in an anaesthetised cat that had CT scan in left lateral recumbency because of trauma and suspected spinal fracture. The heart (H) is displaced to the left

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