Latero‐lateral radiograph of the craniodorsal thorax; cranial is to the left, image on admission. Due to the presence of air in the mediastinum the outlines of the mediastinal contents such as the oesophagus (O), major vessels (A) aorta, (PA) pulmonary arteries, (PV) pulmonary veins, (CVC) caudal vena cava‐cardiac outlines (black arrows) and outlines of the trachea (T) are abnormally well visualised. A pneumomediastinum was diagnosed. (H) heart, (D) diaphragm