Croup, also called acute laryngotracheobronchitis is due to viral infection of the upper airway by parainfluenza virus or respiratory syncytial virus (RSV).
Croup has a peak incidence before the age of 1 (typically between 3 and 6 months of age), and is the most common cause of upper respiratory distress in infants and young children.
Clinically it presents with protracted barking cough and inspiratory stridor due to mucosal oedema resulting in tracheal narrowing.
X rays are not always required, as the diagnosis is often made clinically. X-rays when obtained are usually to exclude other causes of a similar presentation. There are however typical radiographic findings.
- steeple sign - seen on AP radiographs of the neck or chest and neck demonstrates uniform narrowing of the subglottic airway. Also referred to as a 'wine bottle' sign.
- distension of the hypopharynx is also seen due to the patient's attempt at decreasing airway resistance (case 3)
- lateral radiograph of the upper airway will show a normal epiglottis and narrowing of the subglottic region.
Treatment and prognosis
Croup is usually self-limited, with a good prognosis.
Treatment is directed toward improving air exchange. Conservative measures, nebulized racemic epinephrine, and corticosteroids are commonly used.
General imaging differential considerations include
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