eMedicine Specialties > Pediatrics: General Medicine > Infectious Disease

Croup: Differential Diagnoses & Workup

Author: Antonio Muñiz, MD, Associate Professor of Emergency Medicine and Pediatrics, University of Texas Medical School at Houston; Medical Director of the Pediatric Emergency Department, Children's Memorial Hermann Hospital
Coauthor(s): Rona E Molodow, MD, JD, Clinical Professor, Department of Pediatrics, Olive View-University of California Los Angeles Medical Center; Germaine L Defendi, MD, MS, FAAP, Associate Clinical Professor, Department of Pediatrics, Olive View-UCLA Medical Center
Contributor Information and Disclosures

Updated: Nov 18, 2009

Differential Diagnoses

Airway Foreign Body
Mononucleosis and Epstein-Barr Virus Infection
Bacterial Tracheitis
Peritonsillar Abscess
Diphtheria
Retropharyngeal Abscess
Epiglottitis
Sarcoidosis
Inhalation Injury
Subglottic Stenosis
Laryngeal Fractures
Vascular Ring, Right Aortic Arch
Laryngomalacia
Measles

Other Problems to Be Considered

Angioneurotic edema
Allergic reaction
Laryngeal web
Laryngeal papillomatosis
Laryngeal hemangioma
Spasmodic croup
Subglottic hemangioma
Vocal cord paralysis
Uvulitis
Laryngeal tuberculosis
Tracheomalacia
Deep space neck infection
Innominate artery compression
Double aortic arch
Aberrant subclavian artery
Pulmonary artery sling
Wegener granulomatosis
Neoplasm (compressing trachea)

Workup

Laboratory Studies

  • The diagnosis of croup is largely clinical, based on the presenting history and physical examination findings.
  • Laboratory test results rarely contribute to the diagnosis. The CBC count is usually nonspecific, although the WBC count and differential may reveal a viral pattern with lymphocytosis. Identification of specific viruses is also not typically necessary but may be useful in determining isolation needs or, in the case of influenza A, deciding whether antiviral therapy is indicated.
  • ABG measurements are unnecessary and do not reveal hypoxia or hypercarbia unless respiratory fatigue ensues.

Imaging Studies

  • Plain films can verify a presumptive diagnosis or exclude other disorders, such as an aspirated foreign body, epiglottitis, bacterial tracheitis, or retropharyngeal abscess.
  • Plain films should not be used as the only means of making a diagnosis and are not required in uncomplicated cases.
  • The posterior-anterior chest radiograph classically reveals a steeple sign, which signifies subglottic narrowing, whereas the lateral view may reveal a distended hypopharynx (ballooning) during inspiration. However, these findings are not observed in as many as 50% of children with croup. Also, a steeple sign may be observed in patients without croup, representing a false positive.

  • Steeple sign on radiograph.

    Steeple sign on radiograph.

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    Steeple sign on radiograph.

    Steeple sign on radiograph.

Other Tests

  • Although pulse oximetry findings are within the reference range in most patients, such monitoring is helpful to assess the degree of respiratory compromise in severe cases. 
  • Arterial blood gases are unnecessary and show neither hypoxia nor hypercarbia unless respiratory fatigue ensues.

Procedures

  • Laryngoscopy is required only in unusual circumstances (eg, the course of illness is not typical, the child has symptoms that suggest an underlying anatomic or congenital disorder). It may also be required in patients with bacterial tracheitis to obtain the necessary cultures.

More on Croup

Overview: Croup
Differential Diagnoses & Workup: Croup
Treatment & Medication: Croup
Follow-up: Croup
Multimedia: Croup
References
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Further Reading

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Keywords

croup, barking cough, laryngotracheitis, stridor, laryngotracheobronchitis, spasmodic croup, influenza A, inspiratory stridor, parainfluenza virus 1, parainfluenza virus II, parainfluenza virus III, steeple sign, upper respiratory infection

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Contributor Information and Disclosures

Author

Antonio Muñiz, MD, Associate Professor of Emergency Medicine and Pediatrics, University of Texas Medical School at Houston; Medical Director of the Pediatric Emergency Department, Children's Memorial Hermann Hospital
Antonio Muñiz, MD is a member of the following medical societies: American Academy of Emergency Medicine, American Academy of Pediatrics, American College of Emergency Physicians, American Heart Association, American Medical Association, Society for Academic Emergency Medicine, and Southern Medical Association
Disclosure: Nothing to disclose.

Coauthor(s)

Rona E Molodow, MD, JD, Clinical Professor, Department of Pediatrics, Olive View-University of California Los Angeles Medical Center
Rona E Molodow, MD, JD is a member of the following medical societies: American Academy of Pediatrics and American Professional Society on the Abuse of Children
Disclosure: Nothing to disclose.

Germaine L Defendi, MD, MS, FAAP, Associate Clinical Professor, Department of Pediatrics, Olive View-UCLA Medical Center
Germaine L Defendi, MD, MS, FAAP is a member of the following medical societies: Ambulatory Pediatric Association and American Academy of Pediatrics
Disclosure: Nothing to disclose.

Medical Editor

David Jaimovich, MD, Chief Medical Officer, Joint Commission International and Joint Commission Resources
David Jaimovich, MD is a member of the following medical societies: American Academy of Pediatrics
Disclosure: Nothing to disclose.

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from financial planner; Avanir Pharma Stock Investment from financial planner ; WebMD Salary and stock Employment and investment from financial planner

Managing Editor

Joseph Domachowske, MD, Professor of Pediatrics, Microbiology and Immunology, Department of Pediatrics, Division of Infectious Diseases, State University of New York-Upstate Medical University
Joseph Domachowske, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Pediatrics, American Society for Microbiology, Infectious Diseases Society of America, Pediatric Infectious Diseases Society, and Phi Beta Kappa
Disclosure: Nothing to disclose.

CME Editor

Robert W Tolan Jr, MD, Chief, Division of Allergy, Immunology and Infectious Diseases, The Children's Hospital at Saint Peter's University Hospital; Clinical Associate Professor of Pediatrics, Drexel University College of Medicine
Robert W Tolan Jr, MD is a member of the following medical societies: American Academy of Pediatrics, American Medical Association, American Society for Microbiology, American Society of Tropical Medicine and Hygiene, Infectious Diseases Society of America, Pediatric Infectious Diseases Society, Phi Beta Kappa, and Physicians for Social Responsibility
Disclosure: GlaxoSmithKline Honoraria Speaking and teaching; MedImmune Honoraria Speaking and teaching; Merck Honoraria Speaking and teaching; sanofi pasteur Honoraria Speaking and teaching; Baxter Healthcare Honoraria Speaking and teaching

Chief Editor

Russell W Steele, MD, Head, Division of Pediatric Infectious Diseases, Ochsner Children's Health Center; Clinical Professor, Department of Pediatrics, Tulane University School of Medicine
Russell W Steele, MD is a member of the following medical societies: American Academy of Pediatrics, American Association of Immunologists, American Pediatric Society, American Society for Microbiology, Infectious Diseases Society of America, Louisiana State Medical Society, Pediatric Infectious Diseases Society, Society for Pediatric Research, and Southern Medical Association
Disclosure: None None None

 
 
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