pneumonitis, pleurisy, spontaneous pneumothorax, or mass Foreign bodies ingested and lodged in the esophagus can be visualized if radiopaque (e.g., coins) In the cervical esophagus, they will lie flat and be fully visible in the posteroanterior view of the chest A foreign body such as a coin in trachea typically appears “on end” on the posteroanterior view of the chest Airway foreign-body aspiration most frequently manifests, however, by hyperinflation or atelectasis on radiographs because most tracheobronchial foreign bodies are not radiopaque Inspiratory and expiratory films or decubitus CXR may demonstrate focal hyperinflation (i.e., the lobe with an obstructed bronchus remains inflated in expiration or when placed on the dependent side on a decubitus film) Other characteristic radiographic changes include the wide mediastinum from an aortic aneurysm, abnormal cardiac silhouette related to a pericardial effusion or cardiomegaly, rib fractures, or bone changes of metabolic bone derangements A calcified ring may be visualized in approximately one-third of patients with a history of Kawasaki disease The presence of atelectasis may suggest mucous plugging or may be subtle evidence of pulmonary infarction from an embolus or a vasoocclusive crisis of sickle cell anemia The presence of a wedge-shaped pulmonary infiltrate with an ipsilateral elevated hemidiaphragm is suggestive of a pulmonary embolism Studies other than CXR and EKGs are rarely necessary Laboratory studies (such as troponin) are typically not needed in the workup of most patients with chest pain However, if there is clinical suspicion for cardiac abnormalities such as myocarditis, pericarditis, or acute MI based on history or an abnormal EKG, then selective use of a troponin assay is warranted In general, myocarditis is often the cause of increased troponin as the diagnosis of acute MI is extremely low in children Of note, troponin levels may be elevated in noncardiac disease states such as sepsis B-type natriuretic peptide (BNP) can be useful in children with pre-existing heart disease or in those who are in congestive heart failure Toxicologic screens are useful if the patient is considered at risk of drug abuse, particularly cocaine, or if the diagnosis remains unclear An hCG (human chorionic gonadotropin) level should be considered in postpubertal females to assist with diagnosing pregnancy An elevated leukocyte count with a shift to the left may point toward infection as the cause of pain in patients with a systemic illness Examination of a peripheral smear and a hemoglobin electrophoresis are indicated in the child suspected of having sickle cell disease as the cause of chest pain In children with sickle cell disease, a CBC, reticulocyte count, and blood culture are indicated to assist in ascertaining acute chest syndrome or pneumonia, as well as the presence