Does the computed tomographic appearance of the lung differ between young and old dogs?

In computed tomographic (CT) images of humans, decreased lung attenuation, bronchial dilation, and/or thickening, air trapping, cysts, and thickened interlobular septa have been associated with increasing age. To determine if there are differences in the CT appearance of the lungs of young and old dogs that could affect interpretation of diagnostic studies, pulmonary CT images of dogs with conditions unrelated to the thorax were reviewed retrospectively in a case-control study. Computed tomography studies of 42 young dogs (range 0.3-4.8 years) and 47 old dogs (range 9-15.1 years) were jumbled and reviewed by an observer blinded to dog age. Computed tomography was performed under sedation in 62 (70%) dogs and under general anesthesia in 27 (30%). Heterotopic bone was more prevalent (62% vs. 14%) in old dogs. Lung collapse was significantly associated with old age, greater body weight, and anesthesia. There were no significant differences in median lung attenuation or occurrence of ground glass pattern, cysts, bronchial thickening, bronchial dilation, or degree of tracheal calcification. No examples of reticular pattern, emphysema, pleural thickening, or septal thickening were observed in any dog. Despite previous studies describing age-related changes in the radiographic appearance of the lungs of old dogs, it appears that there are minimal observable differences in CT images. Old dogs are more likely to have visible foci of heterotopic bone and may be more prone to lung lobe collapse than young dogs, but neither of these differences should contribute to misdiagnosis of pulmonary disease.