Predictive equations measuring lung and lung lobe volumes in dogs based on thoracic height and width show promise with adjustments for some breeds.

Breed-specific lung lobe volume equations show ~20% error, requiring adjustments especially for brachycephalic breeds.

This retrospective study developed and evaluated predictive equations for total lung volume (TLV) and individual lung lobe volumes in five dog breeds (Shiba Inu, French Bulldog, Chihuahua, Miniature Dachshund, and Toy Poodle) using thoracic CT measurements, specifically thoracic height and width. Forty-seven dogs without respiratory or circulatory disease were included, with CT data collected over approximately six years. Seven lung lobes and the thoracic cavity were volumetrically assessed. Key findings included significant between-breed differences in volumes of the middle lobe, accessory lobe, and caudal part of the left cranial lobe, while the TLV-to-thoracic volume ratio was consistent across breeds. Within most breeds, the combined left cranial lobe (cranial and caudal parts) was volumetrically equivalent to the right cranial lobe. Left and right caudal lobes were similarly matched in volume, as were the middle and accessory lobes in most breeds. Predictive equations derived via linear regression achieved mean error rates of approximately 20%, indicating moderate but imperfect accuracy. The study acknowledges breed-specific anatomical variation—particularly relevant for brachycephalic breeds such as French Bulldogs—as a factor requiring equation adjustments. This baseline dataset of CT-derived lobar volumes by breed may serve as a reference standard for future investigations into pathological changes in pulmonary lobe volumes, surgical planning, and respiratory disease monitoring in dogs.

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