Radiographic reference values for canine baculum length: association with body-weight category in dogs aged at least 1 year.

The canine baculum is routinely visible on abdominal and pelvic radiographs, yet radiographic reference data for its length are scarce. This retrospective single-centre study aimed to characterise radiographic baculum length in male dogs aged at least 1 year and to determine whether baculum length was associated with body-weight category, age, neuter status or mixed-breed status. Lateral radiographs from 62 dogs were reviewed, and baculum length was measured on a single optimal projection. Mean ± SD baculum length increased from 68.4 ± 9.1 mm in dogs < 10 kg to 105.9 ± 26.7 mm in dogs 10-30 kg and 131.2 ± 18.6 mm in dogs > 30 kg (Kruskal-Wallis P < 0.001). In multivariable ordinary least-squares linear regression, body-weight category remained strongly associated with baculum length after adjustment for age, neuter status and mixed-breed status (robust F(2,56) = 67.65, P < 0.001; adjusted R² = 0.609). No evidence of association was detected for age, neuter status or mixed-breed status. These descriptive data may support radiographic interpretation of the canine baculum but should not be used as diagnostic thresholds.