• Bronchiolitis is diagnosed based on patient history & presentation

Diagnostic criteria for bronchiolitis include, but are not limited to, the following:

• Exposure to persons with viral upper respiratory infection
• Preceding upper respiratory illness
• Signs of lower respiratory illness which may include wheezing, retractions, oxygen (O₂₎ desaturation, nasal flaring, & other signs & symptoms described above
• Apnea, especially in premature or low birth-weight infants
• Signs of dehydration

• Wheezes or fine inspiratory crackles with prolonged expiratory phase of breathing
• Barely discernible breath sounds due to bronchiolar obstruction suggest severe disease
• Palpable liver & spleen due to hyperinflation of the lungs

• Eg Complete blood count (CBC) & chest x-ray (CXR) offer little helpful information in bronchiolitis patients
  
  • Chest X-ray (CXR) image may show hyperinflation due to air trapping
  • Chest X-ray (CXR) may be done when the diagnosis is uncertain to rule out other diseases

• Arterial blood gas (ABG) should be considered in patients with severe symptoms of bronchiolitis
• Viral cultures of nasopharyngeal secretions are not recommended

• Viral infections
• Asthma
• Foreign body aspiration
• Anatomic abnormalities (ie tracheoesophageal fistula, laryngeal cleft, airway hemangioma, mediastinal tumor, bronchial cyst, vascular ring)
• Congenital heart disease
• Immunodeficiency states (ie IgA deficiency, AIDS, bronchiectasis)
• Mucociliary clearance disorders (ie cystic fibrosis, primary ciliary dyskinesia)
• Aspiration syndrome (ie gastroesophageal reflux disease, phayngeal dysfunction)
• Anaphylaxis