From the Guidelines
Perihilar interstitial infiltrates in pediatric patients usually indicate viral respiratory infections, particularly bronchiolitis or viral pneumonia. These radiographic findings appear as increased lung markings or haziness around the hilum (where the bronchi and vessels enter the lungs) and often represent inflammation in the small airways and surrounding tissues. The most common causative pathogens include Respiratory syncytial virus (RSV), influenza, adenovirus, and human metapneumovirus 1. Management typically involves supportive care including:
- Adequate hydration
- Fever control with acetaminophen (10-15 mg/kg every 4-6 hours) or ibuprofen (10 mg/kg every 6-8 hours) if age-appropriate
- Respiratory support as needed Antibiotics are generally not indicated unless there is strong suspicion of bacterial superinfection. The infiltrates occur because viral infections trigger inflammatory responses in the bronchiolar epithelium and surrounding interstitium, leading to edema, mucus production, and cellular infiltration that appears as increased density on chest radiographs. While these findings are typically benign and self-limiting in otherwise healthy children, they may represent more serious conditions in immunocompromised patients or those with underlying lung disease, warranting closer monitoring and potentially more aggressive intervention. It's also important to consider the child's overall clinical presentation, including signs of respiratory distress, such as tachypnea, retractions, and grunting, as well as the presence of any underlying comorbid conditions, when determining the need for hospitalization or more intensive management 1. In addition, the American Thoracic Society has published guidelines for the classification, evaluation, and management of childhood interstitial lung disease, which may be relevant in certain cases 1.
From the Research
Perihilar Interstitial Infiltrates in Pediatrics
Perihilar interstitial infiltrates are a common radiographic finding in children under 3 years of age who are hospitalized with acute respiratory symptoms 2. The presence of perihilar interstitial infiltrates can indicate various conditions, including:
- Viral pneumonia, which may be underrecognized and misdiagnosed as certain interstitial lung diseases (ILDs) 3
- Interstitial lung disease (ILD), a group of rare chronic and complex disorders of variable pathology 4, 5
- Acute respiratory distress of unknown cause, which may require lung biopsies for diagnosis 4
Characteristics and Correlations
The degree of perihilar interstitial infiltrates has been correlated with:
- Overinflation (r = 0.45, P < 0.01) 2
- Patient temperature (r = 0.22, P < 0.05) 2
- Antibiotic usage and supplemental oxygen administration 2 However, perihilar interstitial infiltrates are not associated with:
- Duration of admission 2
- Presence of wheeze 2
- Use of nebulized bronchodilators 2
- RSV positivity 2
Diagnostic Approaches
The diagnosis of perihilar interstitial infiltrates can be challenging due to substantial interobserver variability (k = 0.29) 2. A multidisciplinary approach, including clinical, radiological, genetic, and histological findings, is recommended for the diagnosis and management of ILDs 4, 5. High-resolution computed tomography (HRCT) is the best radiological approach for the diagnosis and differential diagnosis of COVID-19 and other ILDs 6.