Viral croup (i.e., acute laryngotracheobronchitis) is an inflammation of the upper airway that occurs in young children. It is most often caused by the parainfluenza virus. This condition is characterized by a barking cough, hoarse voice, and inspiratory stridor, all of which often worsen at night. More severe symptoms are associated with higher degrees of airway obstruction and include , which can rarely progress to respiratory failure. Croup is primarily a clinical diagnosis, and diagnostic studies are only performed for severe disease, diagnostic uncertainty, or recurrent episodes of croup. All patients with viral croup should receive glucocorticoids (preferably dexamethasone) and supportive treatment. Patients with moderate or severe croup should also be evaluated for admission and receive nebulized racemic epinephrine and supplemental oxygen. The prognosis of uncomplicated croup is good, and complete recovery typically occurs within seven days of onset.
- Peak incidence: 6 months to 3 years
- Most common in fall and winter
Epidemiological data refers to the US, unless otherwise specified.
- Important membrane-bound virulence factors of parainfluenza virus include:
- Viral infection → inflammation of the upper airway with edema formation and infiltration of inflammatory cells → narrowing of subglottic airway (inspiratory stridor) and increased work of breathing
- Prodromal phase: 1–2 days of upper respiratory tract infection symptoms (rhinitis, low-grade fever, sore throat) 
- Symptoms of croup ; last 2–7 days and typically manifest in the late evening/night. 
Characteristic features include seal-like barking cough, hoarseness, and inspiratory stridor due to subglottic narrowing. 
- Mild croup: Stridor may be absent or only manifest in agitated individuals.
- Moderate croup
- Severe stridor and dyspnea are present at rest.
- Air entry is decreased.
- Hypoxemia, an altered mental state, and/or other signs of impending respiratory failure may be present.
- Upper airway obstruction can cause pulsus paradoxus. 
- Agitation can worsen symptoms and precipitate complete airway obstruction.
General principles 
- Croup is most commonly diagnosed based on the presence of characteristic .
- Diagnostic studies are not routinely required; do not delay treatment in unstable patients to obtain studies.
- Indications for diagnostic studies include:
- Atypical presentation or diagnostic uncertainty, to rule out
- Severe disease
- Recurrent episodes of croup
Do not delay treatment of stridor to perform diagnostic studies.
- X-ray chest and neck (anteroposterior and lateral) 
- CT chest and neck: usually performed for differential diagnoses or suspected underlying congenital abnormalities 
- Laryngoscopy/bronchoscopy: may be performed for suspected foreign bodies or atypical croup 
- Respiratory viral panel
- CBC: may help distinguish between bacterial and viral infections 
- Blood gas 
Keep the patient calm and minimize distress.
- Allow the patient to maintain a comfortable position (usually semi-upright). 
- Examine the child in the parent's lap. 
- Avoid examining the throat as this may precipitate airway obstruction. 
- Hypoxemia/signs of impending respiratory failure: Initiate immediate stabilization (e.g., supplemental oxygenation, intubation).
- Perform a croup severity assessment to guide treatment; consider using a scoring system (e.g., Westley croup score).
- Regularly reassess patients. 
- Admit patients with severe croup, age < 6 months. , e.g.,
Agitation can worsen symptoms and precipitate complete airway obstruction; keep children calm and defer distressing procedures (e.g., IV placement) until facilities are in place for immediate intubation if required. 
Humidified air, both in the hospital and as a home remedy (e.g., steam inhalation), has been used to treat croup, but there is no evidence that it is effective. 
Immediate stabilization 
- Contact anesthesia or ENT early because children with croup have difficult airways.
- Initiate respiratory support.
- Hypoxemia (e.g., pulse oximetry < 92%) and/or signs of respiratory distress
- Respiratory failure or signs of impending respiratory failure 
Croup severity assessment
- Follow local or institutional protocols where available.
- Croup scoring systems are susceptible to interobserver variability. 
- The most commonly used score is the Westley croup score. 
|Westley croup score |
|Level of consciousness||Normal||0|
Over 80% of croup cases are mild. 
- Give dexamethasone (off-label). 
- Reduces airway swelling within 6 hours
- Effects last up to 72 hours.
- Start supportive care. 
- Moderate croup/severe croup: Add nebulized epinephrine. 
Suspect other upper respiratory infection and if symptoms do not respond to treatments for croup. if there are no symptoms of an
- Discharge home with return precautions can be considered in the following cases:
- Patients with severe croup or other risk factors should be admitted; consider pediatric ICU.
Admission criteria for croup 
|Overview of differential diagnoses of stridor |
|Characteristics||Croup (subglottic laryngitis; laryngotracheitis)|| |
Spasmodic croup (atypical croup) 
|Epiglottitis (supraglottic laryngitis)||Foreign body (FB) aspiration|
|Cause|| || || |
|Onset|| || || || |
| || || || |
|Cough|| || || || || |
|Voice|| || || || || |
|Difficulty swallowing/drooling|| || || || || |
|X-ray neck and chest findings|| |
Response to therapy for croup
| || || |
Additional differential diagnoses 
- Asthma/virus-induced wheeze
- Retropharyngeal abscess
- Bacterial tracheitis
- Subglottic stenosis
- Subglottic hemangioma
The differential diagnoses listed here are not exhaustive.
- The prognosis in uncomplicated cases is good, with full recovery.
- Parents should be aware that croup tends to recur.
- Keep the child calm and allow them to choose a comfortable position.
- Assess for signs of impending respiratory failure; if present contact ENT/anesthesia and prepare for .
- Start supplemental oxygen if needed.
- Give dexamethasone.
- Assess for features of moderate and severe croup; if present give nebulized racemic epinephrine.
- Regularly reassess the patient; start continuous monitoring for patients given nebulized racemic epinephrine.
- Screen for admission criteria for croup and arrange admission if present.