Although investigation of lower respiratory disease is one of the major indicators for thoracic radiology in practice, radiographs can provide information on the other thoracic structures. The heart can be assessed for changes in size and/or shape – an enlarged cardiac silhouette can be seen with myocardial or pericardial disease, while reduced cardiac size can be an indicator of hypovolaemia, while the lungs can be assessed for evidence of congestive failure. Changes to the shape of the heart can indicate enlargement of a specific chamber or vessel. Although many mediastinal structures cannot usually be identified when normal, abnormalities may be readily detected on radiographs. Thoracic lymph node enlargement can be seen as areas of increased opacity in specific locations (e.g. dorsal to the second sternebra for the presternal lymph node), while oesophageal dilation may create the appearance of a tracheal stripe sign and potentially (if severe enough) cause ventral deviation of the trachea. Oesophageal foreign bodies are most commonly located at the thoracic inlet, over the base of the heart or immediately cranial to the diaphragm, and if perforation of the oesophagus has occurred there may be evidence of pneumomediastinum (increased definition of the mediastinal vessels). Pleural effusion and pneumothorax generate typical radiographic changes, and lesions of the thoracic wall (e.g. ribs) can also be identified.