Correlation of thoracic radiograph measurements with age in adolescent Chinese rhesus macaques (Macaca mulatta).

Thoracic radiography has been applied extensively to cardiovascular or respiratory disorders in veterinary practice and in research using animal models. To establish baseline measures for various parameters of thoracic radiography, we used a cross-sectional method to collect the lung length (LL), maximum interior thoracic breadth (TBr), maximum breadth of the cardiac silhouette (CBr), cardiothoracic ratio (CR), and right hilar height ratio (RHHR) of random healthy captive Chinese rhesus monkeys (age, 1 to 5 y; 89 male, 64 female). Significant sex-associated differences occurred in TBr among 1-y-old subjects and RHHR in 2- and 3-y-old monkeys. In addition, LL, TBr, and CBr were significantly correlated with age in both sexes. Finally, stepwise multiple regression revealed that LL and CBr were predictors of age in female monkeys, whereas LL and TBr were age-predictive in male macaques. The current data may suggest caveats regarding the use of thoracic radiography for evaluating disease processes, including pulmonary tuberculosis, hydropericardium, and heart failure, and for assessing physical development in adolescent rhesus macaques.