A pre-surgical auscultation of the heart and lungs can identify some cardiac or respiratory issues that could cause anesthetic problems. However, thoracic radiographs are even more sensitive for identifying issues like cardiac enlargement, collapsing trachea, and various different forms of lung disease that could go undiagnosed without imaging. These disease processes can have minor or major effects on anesthesia and surgery. Correctly identifying them and addressing them as needed can greatly improve anesthesia. In addition, these radiographs can be used as a baseline to identify mild changes in the future that might otherwise go unnoticed.
These are radiographs of the thorax of a dog that was preparing for surgery for the removal of a mass on his leg. Unfortunately, these radiographs show that the cancer has spread to the lungs and surgical removal of the primary tumor on the leg would not be beneficial. Notice the multiple circular white spots through out the lungs? Especially when compared to the normal lungs at the top of the page. These are all metastases of the tumor on the leg.