Viral Pneumonia: This is the most common cause of perihilar prominence in pediatric patients, especially in the emergency room setting. Viral infections such as respiratory syncytial virus (RSV) are prevalent and often present with perihilar infiltrates on chest X-ray.

Asthma: Asthma is a common condition in pediatric patients and can cause perihilar prominence due to bronchial wall thickening and peribronchial cuffing.
Allergic Reaction: An allergic reaction can cause increased bronchial secretions and edema, leading to perihilar prominence on chest X-ray.
Bacterial Pneumonia: While less common than viral pneumonia, bacterial pneumonia can also cause perihilar infiltrates, especially in younger pediatric patients.

Pulmonary Edema: Although less common, pulmonary edema can present with perihilar prominence and is a life-threatening condition that requires prompt recognition and treatment.
Congenital Heart Disease: Certain congenital heart diseases, such as total anomalous pulmonary venous return, can cause perihilar prominence due to increased pulmonary blood flow.
Cystic Fibrosis: Cystic fibrosis is a genetic disorder that can cause chronic pulmonary infections and inflammation, leading to perihilar prominence on chest X-ray.

Lymphoma: Lymphoma is a rare cause of perihilar prominence in pediatric patients, but it can cause mediastinal masses and hilar lymphadenopathy.
Sarcoidosis: Sarcoidosis is a rare condition in pediatric patients, but it can cause hilar lymphadenopathy and perihilar infiltrates.
Histoplasmosis: Histoplasmosis is a fungal infection that can cause perihilar prominence, especially in endemic areas.