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Last updated: March 25, 2020


Croup (acute laryngotracheobronchitis) is one of the most common infectious pediatric emergencies seen in winter. Commonly caused by the parainfluenza virus, croup is characterized by inflammation of the larynx and trachea. The clinical presentation varies depending on the severity of airway obstruction, but typically includes a barking cough, hoarse voice, and inspiratory stridor, all of which tend to occur at night. In moderate to severe cases, respiratory distress with subcostal and intercostal retractions occurs. Croup is primarily a clinical diagnosis, although a chest x-ray may be used to support diagnosis; laboratory tests and pulse oximetry help assess the severity of disease. In mild cases, treatment aims at alleviating symptoms and involves cold, moist air, calming the child, and corticosteroids. Moderate to severe cases require racemic epinephrine. Complications are rare: in cases of respiratory insufficiency, supplemental oxygen is necessary or even sedation and intubation. The prognosis of uncomplicated croup is good, with complete recovery occurring 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.




Clinical features

Prodromal phase

Laryngotracheal inflammation phase

  • Duration: 2–7 days
  • Presentation
    • Symptoms of croup primarily occur during the late evening/night.
    • Mild: seal-like barking cough, hoarseness, and mild inspiratory stridor due to subglottic narrowing
    • Moderate: dyspnea at rest, pronounced thoracic retractions, pallor, tachycardia > 160/min
    • Severe
      • Upper airway obstruction can cause pulsus parodoxus.
      • Severe tachydyspnea at rest with increasing respiratory failure, cyanosis, hypoxemia, bradycardia, and altered mental status.
    • Infants may become agitated as a result of breathing difficulties → worsens agitation and obstruction → in severe cases, exhaustion leads to the infant being unable to breathe on his or her own.



Croup is primarily a clinical diagnosis, but imaging may be considered in mild cases of suspected croup. Other tests (e.g., pulse oximetry, blood gas analysis) help to assess the severity of disease. Identification of the viral pathogen is rarely necessary.

  • Based on clinical findings (see “Symptoms/clinical findings” above)
  • Pulse oximetry
  • X-ray of chest and neck: helps to verify subglottic narrowing, usually called steeple sign
  • In suspected cases of respiratory insufficiency: blood gas analysis (BGA)
  • If pneumonia or bacterial tracheitis is suspected: CBC
  • PCR: To identify the viral pathogen in tissue (e.g., nasopharyngeal washing)


Differential diagnoses

Croup (subglottic laryngitis; laryngotracheitis) Epiglottitis (supraglottic laryngitis)

Laryngeal diphtheria

Foreign body (FB) aspiration
  • Accidental aspiration of a foreign body (e.g., nuts, raisins, seeds, pieces of toys)
  • Slow: 12–48 hours
  • Sudden: 4–12 hours
  • Initially slow, then sudden onset of symptoms after 4–5 days
  • Sudden
  • If the initial aspiration and choking episode is not witnessed, onset of symptoms (persistent or recurrent cough) days or weeks later
General condition
  • Does not appear toxic
  • Toxic appearance, possible swollen neck
  • Barking
  • Absent
  • Barking
  • Choking
  • Hoarse
  • Muffled
  • Hoarse
  • Hoarseness or inability to speak indicate a laryngotracheal FB
Difficulty swallowing/drooling
  • Absent
  • Present
  • Present
  • Depends on the location of the FB
X-ray findings
  • Most FB are radiolucent; focal overinflation of the distal lung may be visible
  • Approx. 16% of FB in larynx or trachea and 60% in the right lung
Response to inhalators
  • Mild croup: improvement after cool mist inhalation
  • Moderate to severe croup: improvement after epinephrine inhalation
  • No improvement
  • No improvement
  • No improvement
  • Removal of FB via rigid bronchoscopy
  • Heimlich maneuver if the child is in respiratory distress and cannot speak or cry




The differential diagnoses listed here are not exhaustive.


Severity Treatment
Mild croup
  • Decrease infant's anxiety
  • Cool mist inhalation
  • Placing infant to sleep in an upright position
  • Breathing cool air at night (especially in the winter) helps to soothe symptoms
  • Dexamethasone
    • Reduces airway swelling within 6 hours
    • Long-lasting effect
    • Oral syrup, IV or IM injection
Moderate to severe croup

Intubation in severe croup is difficult due to subglottic narrowing → anesthesiologist required!




We list the most important complications. The selection is not exhaustive.


  • The prognosis in uncomplicated cases is good, with full recovery.
  • Parents should be aware that croup tends to recur.



  1. Le T, Bhushan V, Bagga HS. First Aid for the USMLE Step 2 CK. McGraw-Hill Medical ; 2009
  2. Woods CR. Croup: Approach to Management. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/croup-approach-to-management.Last updated: August 2, 2016. Accessed: March 18, 2017.
  3. Simons KJ, Simons FER. Epinephrine and its use in anaphylaxis: current issues. Curr Opin Allergy Clin Immunol. 2010; 10 (4): p.354-361.
  4. Defendi GL. Croup. In: Steele RW, Croup. New York, NY: WebMD. http://emedicine.medscape.com/article/962972. Updated: September 27, 2016. Accessed: March 18, 2017.
  5. Woods CR. Patient education: Croup in infants and children (Beyond the Basics). In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. http://www.uptodate.com/contents/croup-in-infants-and-children-beyond-the-basics.Last updated: May 6, 2016. Accessed: March 18, 2017.
  6. Lowen AC, Mubareka S, Steel J, Palese P. Influenza virus transmission is dependent on relative humidity and temperature. PLos Pathog. 2007; 3 (10): p.1470-6. doi: 10.1371/journal.ppat.0030151 . | Open in Read by QxMD
  7. Woods CR. Croup: Clinical Features, Evaluation, and Diagnosis. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/croup-clinical-features-evaluation-and-diagnosis.Last updated: May 10, 2016. Accessed: March 18, 2017.
  8. Steeple Sign (Trachea). https://radiopaedia.org/articles/steeple-sign-trachea. . Accessed: March 18, 2017.
  9. Lovinsky-Desir S. Laryngomalacia. In: Windle ML, Laryngomalacia. New York, NY: WebMD. https://emedicine.medscape.com/article/1002527. Updated: April 21, 2017. Accessed: December 12, 2017.
  10. Concepcion E. Pediatric Airway Foreign Body. In: Sharma GD, Pediatric Airway Foreign Body. New York, NY: WebMD. http://emedicine.medscape.com/article/1001253. Updated: October 13, 2015. Accessed: February 18, 2017.
  11. Ruiz FE. Airway Foreign Bodies in Children. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/airway-foreign-bodies-in-children.Last updated: April 6, 2016. Accessed: February 18, 2017.
  12. Luszczak M. Evaluation and management of infants and young children with fever. Am Fam Physician. 2001; 64 (7): p.1219-1227.
  13. Epiglottitis. https://radiopaedia.org/articles/epiglottitis. . Accessed: March 18, 2017.
  14. Herold G. Internal Medicine. Herold G ; 2014
  15. Le T, Bhushan V, Chen V, King M. First Aid for the USMLE Step 2 CK. McGraw-Hill Education ; 2015
  16. UpToDate. Westley croup severity score. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/image?imageKey=PEDS%2F100744&topicKey=PEDS%2F6004&rank=1~60&source=see_link&search=croup&utdPopup=true.Last updated: January 1, 2017. Accessed: March 18, 2017.
  17. Patient Care Part 1. http://www.cumc.columbia.edu/harlemhospital/surgery-residency/generalsurgerydept/Patient%20Care%20part1. . Accessed: March 18, 2017.
  18. Rosenfeld GC, Loose DS. Pharmacology. LWW ; 2013