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Charles R Woods, MD, MSSection Editors

Sheldon L Kaplan, MDGregory Redding, MD

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Carrie Armsby, MD, MPH

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Croup: Clinical features, evaluation, and diagnosis

All topics are updated as new evidence becomes available and our peer review process is complete.Literature review current through: Oct 2015. | This topic last updated: Feb 18, 2015.

INTRODUCTION — Croup is a respiratory illness characterized by inspiratory stridor, cough, and hoarseness.These symptoms result from inflammation in the larynx and subglottic airway. A barking cough is the hallmark ofcroup among infants and young children, whereas hoarseness predominates in older children and adults.Although croup usually is a mild and self­limited illness, significant upper airway obstruction, respiratory distress,and, rarely, death, can occur.

The clinical features, evaluation, and diagnosis of croup will be discussed here. The management of croup isdiscussed separately. (See "Croup: Approach to management" and "Croup: Pharmacologic and supportiveinterventions".)

DEFINITIONS — The term croup has been used to describe a variety of upper respiratory conditions in children,including laryngitis, laryngotracheitis, laryngotracheobronchitis, bacterial tracheitis, or spasmodic croup [1].These terms are defined below. In the past, the term croup also has been applied to laryngeal diphtheria(diphtheritic or membranous croup), which is discussed separately. (See "Epidemiology and pathophysiology ofdiphtheria" and "Clinical manifestations, diagnosis and treatment of diphtheria".)

Throughout this review, the term croup will be used to refer to laryngotracheitis. Laryngotracheobronchitis,laryngotracheobronchopneumonitis, bacterial tracheitis, and spasmodic croup are designated specifically assuch.

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Laryngitis refers to inflammation limited to the larynx and manifests itself as hoarseness [2]. It usuallyoccurs in older children and adults and, similar to croup, is frequently caused by a viral infection. Theetiology, management, and evaluation of other causes of hoarseness are discussed in detail separately.(See "Hoarseness in children: Etiology and management" and "Hoarseness in children: Evaluation".)

Laryngotracheitis (croup) refers to inflammation of the larynx and trachea [2]. Although lower airway signsare absent, the typical barking cough will be present.

Laryngotracheobronchitis (LTB) occurs when inflammation extends into the bronchi, resulting in lowerairway signs (eg, wheezing, crackles, air trapping, increased tachypnea) and sometimes more severeillness than laryngotracheitis alone [2]. This term commonly is used interchangeably with laryngotracheitis,and the entities are often indistinct clinically. Further extension of inflammation into the lower airwaysresults in laryngotracheobronchopneumonitis, which sometimes can be complicated by bacterialsuperinfection. Bacterial superinfection can be manifest as pneumonia, bronchopneumonia, or bacterialtracheitis.

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ETIOLOGY — Croup is usually caused by viruses. Bacterial infection may occur secondarily, as described

above.

Parainfluenza virus type 1 is the most common cause of acute laryngotracheitis, especially the fall and winter

epidemics [4­6]. Parainfluenza type 2 sometimes causes croup outbreaks, but usually with milder disease than

type 1. Parainfluenza type 3 causes sporadic cases of croup that often are more severe than those due to types

1 and 2. In multicenter surveillance of children <5 years who were hospitalized with febrile or acute respiratory

illnesses, 43 percent of children with confirmed parainfluenza infection were diagnosed with croup [7]. Croup

was the most common discharge diagnosis for children with confirmed parainfluenza 1 (42 percent) and

parainfluenza 2 (48 percent) infections but was only diagnosed in 11 percent of children with confirmed

parainfluenza 3 infections.

The microbiology, pathogenesis, and epidemiology of parainfluenza infections are discussed separately. (See

"Parainfluenza viruses in children".)

A number of other viruses that typically cause lower respiratory tract disease also can cause upper respiratory

tract symptoms, including croup, as described below [6].

Bacterial tracheitis (also called bacterial croup) describes bacterial infection of the subglottic trachea,

resulting in a thick, purulent exudate, which causes symptoms of upper airway obstruction (picture 1). The

bronchi and lungs are typically involved, as well (ie, bacterial tracheobronchitis). Bacterial tracheitis may

occur as a complication of viral respiratory infections (usually those which manifest themselves as LTB or

laryngotracheobronchopneumonitis) or as a primary bacterial infection. (See "Bacterial tracheitis in

children: Clinical features and diagnosis".)

Spasmodic croup is characterized by the sudden onset of inspiratory stridor at night, short duration

(several hours), and sudden cessation [2]. This is often in the setting of a mild upper respiratory infection,

but without fever or inflammation. A striking feature of spasmodic croup is its recurrent nature, hence the

alternate descriptive term, "frequently recurrent croup". Because of some clinical overlap with atopic

diseases, it is sometimes referred to as "allergic croup".

We consider "spasmodic croup" to be distinct from "atypical croup," although the terms are sometimes

used interchangeably. Atypical croup may be defined as recurrent episodes of croup­like symptoms

occurring beyond the typical age range of six months to three years for "viral croup" or recurrent episodes

that do not appear to be simple "spasmodic croup" [3].

Respiratory syncytial virus (RSV) and adenoviruses are relatively frequent causes of croup. The

laryngotracheal component of disease is usually less significant than that of the lower airways. (See

"Respiratory syncytial virus infection: Clinical features and diagnosis", section on 'Clinical manifestations'

and "Epidemiology and clinical manifestations of adenovirus infection", section on 'Clinical presentation'.)

Human coronavirus NL63 (HCoV­NL63), first identified in 2004, has been implicated in croup and other

respiratory illnesses [8­10]. The prevalence of HCoV­NL63 varies geographically. (See "Coronaviruses",

section on 'Respiratory'.)

Measles is an important cause of croup in areas where measles remains prevalent. (See "Clinical

manifestations and diagnosis of measles".)

Influenza virus is a relatively uncommon cause of croup. However, children hospitalized with influenzal

croup tend to have longer hospitalization and greater risk of readmission for relapse of laryngeal symptoms

than those with parainfluenzal croup. (See "Seasonal influenza in children: Clinical features and

diagnosis".)

Rhinoviruses, enteroviruses (especially Coxsackie types A9, B4, and B5, and echovirus types 4, 11, and

21), and herpes simplex virus are occasional causes of sporadic cases of croup that are usually mild. (See

appropriate topic reviews).

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Croup also may be caused by bacteria. Mycoplasma pneumoniae has been associated with mild cases of croup.In addition, secondary bacterial infection may occur in children with laryngotracheitis, laryngotracheobronchitis,or laryngotracheobronchopneumonitis. The most common secondary bacterial pathogens includeStaphylococcus aureus, Streptococcus pyogenes, and S. pneumoniae [1].

EPIDEMIOLOGY — Croup most commonly occurs in children 6 to 36 months of age. It is seen in youngerinfants (as young as three months) and in preschool children, but it is rare beyond age six years [1,12]. It is morecommon in boys, with a male:female ratio of about 1.4:1 [1,12­14].

Family history of croup is a risk factor for croup and recurrent croup. In a case­control study, children whoseparents had a history of croup were 3.2 times as likely to have an episode of croup and 4.1 times as likely tohave recurrent croup as children with no parental history of croup [15]. Parental smoking, a well­recognized riskfactor for respiratory tract infections in children, does not appear to increase the risk of croup [15,16]. (See"Secondhand smoke exposure: Effects in children", section on 'Respiratory symptoms and illness'.)

Most cases of croup occur in the fall or early winter, with the major incidence peaks coinciding withparainfluenza type 1 activity (often in October) and minor peaks occurring during periods of respiratory syncytialvirus or influenza virus activity. (See "Respiratory syncytial virus infection: Clinical features and diagnosis",section on 'Seasonality' and "Seasonal influenza in children: Clinical features and diagnosis", section on'Influenza activity'.)

Emergency department (ED) visits for croup are most frequent between 10:00 PM and 4:00 AM. However,children seen for croup between noon and 6:00 PM are more likely to be admitted to the hospital [4,17]. Amorning peak between 7:00 AM and 11:00 AM in ED visits for croup also has been noted [14].

Hospital admissions for croup have declined steadily since the late 1970s. In an analysis of data from theNational Hospital Discharge Surveys from 1979 through 1997, the estimated number of annual hospitalizationsfor croup decreased from 48,900 to 33,500 [5]. Estimates of annual hospitalization rates for croup caused byparainfluenza virus types 1 to 3 from 1994 to 1997 were 0.4 to 1.1 per 1000 children for children younger thanone year and 0.24 to 0.61 per 1000 children for children between one and four years. Approximately one­half ofthese hospitalizations were attributed to parainfluenza type 1.

In a six­year (1999 to 2005) population­based study, 5.6 percent of children with a diagnosis of croup in the EDrequired hospital admission. Among those discharged home, 4.4 percent had a repeat ED visit within 48 hours[14].

PATHOGENESIS — The viruses that cause croup typically infect the nasal and pharyngeal mucosal epitheliainitially and then spread locally along the respiratory epithelium to the larynx and trachea.

The anatomic hallmark of croup is narrowing of the trachea in the subglottic region. This portion of the trachea issurrounded by a firm cartilaginous ring such that any inflammation results in narrowing of the airway. In additionto this "fixed" obstruction, dynamic obstruction of the extrathoracic trachea below the cartilaginous ring mayoccur when the child struggles, cries, or becomes agitated. The dynamic obstruction occurs as a result of thecombination of high negative pressure in the distal extrathoracic trachea and the floppiness of the tracheal wallin children.

Laryngoscopic evaluation of patients during acute laryngotracheitis shows redness and swelling of the lateralwalls of the trachea. In severe cases, the subglottic airway may be reduced to a diameter of 1 to 2 mm. Inaddition to mucosal edema and swelling, fibrinous exudates and, occasionally, pseudomembranes can build upon the tracheal surfaces and contribute to airway narrowing. The vocal cords and laryngeal tissues also canbecome swollen, and cord mobility may be impaired [2,18­20]. Autopsy studies in children with laryngotracheitisshow infiltration of histiocytes, lymphocytes, plasma cells, and neutrophils into edematous lamina propria,

Metapneumoviruses cause primarily lower respiratory tract disease similar to RSV, but upper respiratorytract symptoms have been described in some patients [11]. (See "Human metapneumovirus infections".)

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submucosa, and adventitia of the larynx and trachea [21­23].

In spasmodic croup, findings on direct laryngoscopy demonstrate noninflammatory edema [18]. This suggeststhat there is no direct viral involvement of the tracheal epithelium.

Patients with bacterial tracheitis have a bacterial superinfection that causes thick pus to develop within thelumen of the subglottic trachea (picture 1). Ulcerations, pseudomembranes, and microabscesses of the mucosalsurface occur. The supraglottic tissues usually are normal. (See "Bacterial tracheitis in children: Clinical featuresand diagnosis", section on 'Pathogenesis and pathology'.)

Host factors — Only a small fraction of children with parainfluenza virus infections develop overt croup. Thissuggests that host (or genetic) factors play a role in the pathogenesis. Host factors that may contribute to thedevelopment of croup include functional or anatomic susceptibility to upper airway narrowing, variations inimmune response, and predisposition to atopy [14].

Underlying host factors that predispose to clinically significant narrowing of the upper airway include:

The potential role of the immune response was demonstrated in studies that demonstrated increased productionof parainfluenza virus­specific IgE and increased lymphoproliferative response to parainfluenza virus antigen,and diminished histamine­induced suppression of lymphocyte transformation responses to parainfluenza virus inchildren with parainfluenza virus and croup compared with those with parainfluenza virus without croup [27,28].

CLINICAL PRESENTATION — The clinical presentation of croup depends upon the specific croup syndromeand the degree of upper airway obstruction. Although croup usually is a mild and self­limited illness, specificfeatures of the history and physical examination identify children who are seriously ill or at risk for rapidprogression of disease. (See 'Evaluation' below.)

Laryngotracheitis — Laryngotracheitis typically occurs in children three months to three years of age [2]. Theonset of symptoms is usually gradual, beginning with nasal irritation, congestion, and coryza. Symptomsgenerally progress over 12 to 48 hours to include fever, hoarseness, barking cough, and stridor. Respiratorydistress increases as upper airway obstruction becomes more severe. Rapid progression or signs of lowerairway involvement suggests a more serious illness. Cough usually resolves within three days [29]; othersymptoms may persist for seven days with a gradual return to normal [2]. Deviations from this expected courseshould prompt consideration of diagnoses other than laryngotracheitis. (See 'Differential diagnosis' below.)

The degree of upper airway obstruction is evident on physical examination, as described below. In mild cases,the child is hoarse and has nasal congestion. There is minimal, if any, pharyngitis. As airway obstructionprogresses, stridor develops, and there may be mild tachypnea with a prolonged inspiratory phase. Thepresence of stridor is a key element in the assessment of severity. Stridor at rest is a sign of significant upperairway obstruction. As upper airway obstruction progresses, the child may become restless or anxious. (See'Severity assessment' below.)

When airway obstruction becomes severe, suprasternal, subcostal, and intercostal retractions may be seen.Breath sounds can be diminished. Agitation, which generally is accompanied by increased inspiratory effort,exacerbates the subglottic narrowing by creating negative pressure in the airway. This can lead to furtherrespiratory distress and agitation.

Anatomic narrowing of the airway, from etiologies such as subglottic stenosis, laryngeal webs,tracheomalacia, laryngomalacia, laryngeal clefts, or subglottic hemangiomas [3]

Hyperactive airways, perhaps aggravated by atopy or gastroesophageal reflux, as suggested in somechildren with spasmodic croup or recurrent croup [24­26]

Acquired airway narrowing from respiratory tract papillomas (human papillomavirus), post­intubationscarring, or irritation from aspirations associated with gastroesophageal reflux

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Hypoxia and cyanosis can develop, as can respiratory fatigue from sustained increased respiratory effort. Highrespiratory rates also tend to correlate with the presence of hypoxia. Without intervention, the hypoxia or fatiguecan sometimes lead to death.

Spasmodic croup — Spasmodic croup also occurs in children three months to three years of age [2]. Incontrast to laryngotracheitis, spasmodic croup always occurs at night; the duration of symptoms is short, oftenwith symptoms subsiding by the time of presentation for medical attention; and the onset and cessation ofsymptoms are abrupt. Fever is typically absent, but mild upper respiratory tract symptoms (eg, coryza) may bepresent. Episodes can recur within the same night and for two to four successive evenings [30]. A strikingfeature of spasmodic croup is its recurrent nature, hence the alternate descriptive term, "frequently recurrentcroup". There may be a familial predisposition to spasmodic croup, and it may be more common in children witha family history of allergies [24].

Early in the clinical course, spasmodic croup may be difficult to distinguish from laryngotracheitis. As the courseprogresses, the episodic nature of spasmodic croup and relative wellness of the child between attacksdifferentiate it from classic croup, in which the symptoms are continuous.

Although the initial presentation can be dramatic, the clinical course is usually benign. Symptoms are almostalways relieved by comforting the anxious child and administering humidified air. Rarely, children may benefitfrom treatment with corticosteroids and/or nebulized epinephrine [31]. Other therapies generally are notindicated. (See "Croup: Approach to management".)

Bacterial tracheitis — Bacterial tracheitis may present as a primary or secondary infection [32]. In primaryinfection, there is acute onset of symptoms of upper airway obstruction with fever and toxic appearance. Insecondary infection, there is marked worsening during the clinical course of viral laryngotracheitis, with highfever, toxic appearance, and increasing respiratory distress secondary to tracheal obstruction from purulentsecretions. In both of these presentations, signs of lower airway disease, such as crackles and wheezes, maybe present. However, the upper airway obstruction is the more clinically significant manifestation [2,33]. (See"Bacterial tracheitis in children: Clinical features and diagnosis", section on 'Clinical features'.)

Recurrent croup — A child who has had recurrent episodes of classic viral croup may have an underlyingcondition that predisposes him or her to develop clinically significant narrowing of the upper airway. Recurrentepisodes of croup­like symptoms occurring outside the typical age range for "viral croup" (ie, six months to threeyears) and recurrent episodes that do not appear to be simple "spasmodic croup" should raise suspicion forlarge airway lesions, gastroesophageal reflux or eosinophilic esophagitis, or atopic conditions [3,34­38].

Children with recurrent croup may require radiographic evaluation or bronchoscopy. (See 'Host factors' aboveand 'Imaging' below.)

EVALUATION

Overview — The evaluation of children with suspected croup has several objectives, including promptidentification of patients with significant upper airway obstruction or at risk for rapid progression of upper airwayobstruction. In addition, there are some conditions with presentations similar to that of croup that require specificevaluations and/or interventions; these too must be promptly identified. (See 'Differential diagnosis' below.)

During the evaluation, efforts should be made to make the child as comfortable as possible. The increasedinspiratory effort that accompanies anxiety and fear in young children can exacerbate subglottic narrowing,further diminishing air exchange and oxygenation. (See 'Pathogenesis' above.)

Rapid assessment and initial management — Rapid assessment of general appearance (including thepresence of stridor at rest), vital signs, pulse oximetry, airway stability, and mental status is necessary to identifychildren with severe respiratory distress and/or impending respiratory failure. (See "Croup: Approach tomanagement", section on 'Respiratory care'.)

Endotracheal intubation is required in less than 1 percent of children with croup who are seen in the emergency

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department. However, the need for endotracheal intubation should be anticipated in children with progressiverespiratory failure so that it can be performed in as controlled a setting as possible. Respiratory failure isheralded by the following signs [1,39,40]:

A tracheal tube that is 0.5 to 1 mm smaller than would typically be used may be required. (See "Emergencyendotracheal intubation in children", section on 'Endotracheal tube'.)

In addition to establishment of an airway, children who have severe respiratory distress require immediatepharmacologic treatment, including administration of nebulized epinephrine and systemic or nebulizedcorticosteroids. (See "Croup: Approach to management", section on 'Moderate to severe croup'.)

Once control of the airway is established and pharmacologic treatment, if necessary, is under way, theremainder of the evaluation can proceed.

History — The history should include a description of the onset, duration, and progression of symptoms.Factors that are associated with increased severity of illness include:

Aspects of the history that are helpful in distinguishing croup from other causes of acute upper airwayobstruction include [1,41]:

The differential diagnosis of croup is discussed in greater detail below. (See 'Differential diagnosis' below.)

Examination — The objectives of the examination of the child with croup include assessment of severity ofupper airway obstruction and exclusion of other infectious and non­infectious causes of acute upper airway

Fatigue and listlessnessMarked retractions (although retractions may decrease with increased obstruction and decreased air entry)Decreased or absent breath soundsDepressed level of consciousnessTachycardia out of proportion to feverCyanosis or pallor

Sudden onset of symptomsRapidly progressing symptoms (ie, symptoms of upper airway obstruction after fewer than 12 hours ofillness)

Previous episodes of croupUnderlying abnormality of the upper airwayMedical conditions that predispose to respiratory failure (eg, neuromuscular disorders)

Fever – The absence of fever from onset of symptoms to the time of presentation is suggestive ofspasmodic croup or a noninfectious etiology (eg, foreign body aspiration or ingestion, acute angioneuroticedema).

Hoarseness and barking cough – Hoarseness and barking cough, characteristic findings in croup, aretypically absent in children with acute epiglottitis, foreign body aspiration, and angioneurotic edema.

Difficulty swallowing – Difficulty swallowing may occur in acute epiglottitis and foreign body aspiration. Alarge ingested foreign body may lodge in the upper esophagus, where it distorts and narrows the uppertrachea, thus mimicking the croup syndrome (including barking cough and inspiratory stridor).

Drooling – Drooling may occur in children with peritonsillar or retropharyngeal abscesses, retropharyngealcellulitis, and epiglottitis. In an observational study, drooling was present in approximately 80 percent ofchildren with epiglottitis, but only 10 percent of those with croup [41].

Throat pain – Complaints of dysphagia and sore throat are more common in children with epiglottitis thancroup (approximately 60 to 70 percent versus <10 percent) [41].

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obstruction, both of which are necessary in making management decisions.

The initial examination often can be accomplished by observing the child in a comfortable position with the

caretaker. Every effort should be made to measure the child's weight and vital signs.

Aspects of the examination that are helpful in assessing the degree of upper airway obstruction and severity of

illness include:

These aspects of the examination are often used in clinical scoring systems to evaluate the severity of illness

and/or in making decisions regarding the need for hospital admission. (See 'Severity assessment' below and

"Croup: Approach to management", section on 'Observation and disposition'.)

Components of the examination that are useful in distinguishing croup from other causes of acute upper airway

obstruction include [39,41]:

Overall appearance – Is the child comfortable and interactive, anxious and quiet, or obtunded? Is there

stridor at rest? Stridor at rest is a sign of significant upper airway obstruction. Children with significant

upper airway obstruction may prefer to sit up and lean forward in a "sniffing" position (neck is mildly flexed,

and head is mildly extended). This position tends to improve the patency of the upper airway.

Quality of the voice – Does the child have a hoarse or diminished cry? Is the voice muffled? A muffled "hot

potato" voice is suggestive of epiglottitis, retropharyngeal abscess, or peritonsillar abscess.

Degree of respiratory distress – Signs of respiratory distress include tachypnea, hypoxemia, and increased

work of breathing (intercostal, subcostal, or suprasternal retractions; nasal flaring; grunting; use of

accessory muscles)

Tidal volume – Does there appear to be good chest expansion with inspiration, indicating adequate air

entry?

Lung examination – Are there abnormal respiratory sounds during inspiration or expiration? Inspiratory

stridor indicates upper airway obstruction, whereas expiratory wheezing is a sign of lower airway

obstruction. If there is stridor, is it present at rest or only with agitation? As discussed above, stridor at rest

is a sign of significant upper airway obstruction. Stridor will be more obvious on auscultation, since the

inspiratory noise is transmitted through the chest. The presence of crackles (rales) also suggests lower

respiratory tract involvement (eg, laryngotracheobronchitis, laryngotracheobronchopneumonitis, or

bacterial tracheitis).

Assessment of hydration status – Decreased oral intake and increased insensible losses from fever and

tachypnea may result in dehydration. (See "Clinical assessment and diagnosis of hypovolemia

(dehydration) in children".)

Preferred posture – Children with epiglottitis usually prefer to sit up in the "tripod" or "sniffing position"

(picture 2A­B).

Examination of the oropharynx for the following signs:

Cherry red, swollen epiglottis, suggestive of epiglottitis•

Pharyngitis, typically minimal in laryngotracheitis, may be more pronounced in epiglottitis or laryngitis•

Excessive salivation, suggestive of acute epiglottitis, peritonsillar abscess, or retropharyngeal

abscess

•

Diphtheritic membrane•

Tonsillar asymmetry or deviation of the uvula suggestive of peritonsillar abscess•

Midline or unilateral swelling of the posterior pharyngeal wall suggestive of retropharyngeal abscess•

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The differential diagnosis of croup is discussed in greater detail below. (See 'Differential diagnosis' below.)

Severity assessment — The severity of croup is often determined by the clinical scoring systems. Althoughthere are a number of validated croup scoring systems, the Westley croup score [43] has been the mostextensively studied; it is described below. No matter which system is used to assess severity, the presence ofchest wall retractions and stridor at rest are the two critical clinical features.

The elements of the Westley croup score describe key features of the physical examination [43]. Each elementis assigned a score, as illustrated below:

Mild croup is defined by a Westley croup score of ≤2. Typically, these children have a barking cough and hoarsecry, but no stridor at rest. Children with mild croup may have stridor when upset or crying (ie, agitated) and eitherno, or only mild, chest wall/subcostal retractions [1,39].

Moderate croup is defined by a Westley croup score of 3 to 7. Children with moderate croup have stridor at rest,at least mild retractions, and may have other symptoms or signs of respiratory distress, but little or no agitation[1,39].

Severe croup is defined by a Westley croup score of ≥8. Children with severe croup have significant stridor atrest, although stridor may decrease with worsening upper airway obstruction and decreased air entry [1,39].Retractions are severe (including indrawing of the sternum) and the child may appear anxious, agitated, orfatigued. Prompt recognition and treatment of children with severe croup are paramount.

Imaging

Indications — Radiographic confirmation of acute laryngotracheitis is not required in the vast majority ofchildren with croup. Radiographic evaluation of the chest and/or upper trachea is indicated if the diagnosis is inquestion, the course is atypical, an inhaled or swallowed foreign body is suspected (although the majority arenot radio­opaque), croup is recurrent, and/or there is a failure to respond as expected to therapeuticinterventions. (See 'Differential diagnosis' below and "Croup: Approach to management".)

Findings — In children with croup, a posterior­anterior chest radiograph demonstrates subglottic narrowing,commonly called the "steeple sign" (image 1). The lateral view may demonstrate overdistention of thehypopharynx during inspiration [44] and subglottic haziness (image 2). The epiglottis should have a normalappearance.

Concerns have been raised about safety of examining the pharynx in children with upper airwayobstruction and possible epiglottitis since such efforts have been reported to precipitatecardiorespiratory arrest. However, in two series, each including more than 200 patients withepiglottitis or viral croup, direct examination of the oropharynx was not associated with sudden clinicaldeterioration [32,42].

Examination of the cervical lymph nodes, which can be enlarged in patients with retropharyngeal orperitonsillar abscesses.

Other physical findings may be present, depending on the particular inciting virus. As an example, rash,conjunctivitis, exudative pharyngitis, and adenopathy are suggestive of adenovirus infection.

Otitis media (acute or with effusion) may be present as a primary viral or secondary bacterial process.

Level of consciousness: Normal, including sleep = 0; disoriented = 5Cyanosis: None = 0; with agitation = 4; at rest = 5Stridor: None = 0; with agitation = 1; at rest = 2Air entry: Normal = 0; decreased = 1; markedly decreased = 2Retractions: None = 0; mild = 1; moderate = 2; severe = 3

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In contrast, the lateral radiograph in virtually all children with epiglottitis demonstrates swelling of the epiglottis,

sometimes called the "thumb sign" (image 3). (See "Epiglottitis (supraglottitis): Clinical features and diagnosis",

section on 'Radiographic features'.)

The lateral radiograph in children with bacterial tracheitis may demonstrate only nonspecific edema or

intraluminal membranes and irregularities of the tracheal wall (image 4) [45].

Laboratory studies — Laboratory studies, which are rarely indicated in children with croup, are of limited

diagnostic utility but may help guide management in more severe cases.

Blood tests — The white blood cell (WBC) count can be low, normal, or elevated; WBC counts >10,000

cells/microL are common. Neutrophil or lymphocyte predominance may be present on the differential [46,47].

The presence of a large number of band­form neutrophils is suggestive of primary or secondary bacterial

infection. Croup is not associated with any specific alterations in serum chemistries.

Microbiology — Confirmation of etiologic diagnosis is not necessary for most children with croup, since

croup is a self­limited illness that usually requires only symptomatic therapy. When an etiologic diagnosis is

necessary, viral culture and/or rapid diagnostic tests that detect viral antigens are performed on secretions from

the nasopharynx or throat. (See 'Etiologic diagnosis' below.)

DIAGNOSIS

Clinical diagnosis — The diagnosis of croup is clinical, based on the presence of a barking cough and stridor,

especially during a typical community epidemic of one of the causative viruses. (See 'Etiology' above.)

Neither radiographs nor laboratory tests are necessary to make the diagnosis. However, radiographs may be

helpful in excluding other causes if the diagnosis is in question. (See 'Differential diagnosis' below.)

Etiologic diagnosis — Although not typically required in most cases of croup, identification of a specific viral

etiology may be necessary to make decisions regarding isolation for patients requiring hospitalization or for

public health/epidemiologic monitoring purposes. Testing for influenza is indicated if the results will influence

decisions regarding treatment, prophylaxis of contacts, or performance of other diagnostic tests; laboratory

confirmation should not delay the initiation of antiviral therapy for influenza when clinical and seasonal

considerations are compatible with influenza as the potential etiology of croup. (See "Seasonal influenza in

children: Clinical features and diagnosis", section on 'Laboratory diagnosis' and "Seasonal influenza in children:

Prevention and treatment with antiviral drugs", section on 'Timing of treatment'.)

Diagnosis of a specific viral etiology can be made by viral culture of secretions from the nasopharynx or throat.

Rapid tests that detect viral antigens in these secretions are commercially available for many respiratory viruses.

The diagnosis of specific viral infections is discussed in detail in individual topic reviews:

Parainfluenza (see "Parainfluenza viruses in children", section on 'Diagnosis')

Influenza (see "Seasonal influenza in children: Clinical features and diagnosis", section on 'Diagnosis')

Respiratory syncytial virus (see "Respiratory syncytial virus infection: Clinical features and diagnosis",

section on 'Laboratory diagnosis')

Adenovirus (see "Diagnosis, treatment, and prevention of adenovirus infection", section on 'Diagnostic

tests of choice for different adenovirus syndromes')

Measles (see "Clinical manifestations and diagnosis of measles", section on 'Diagnosis')

Enteroviruses (see "Clinical manifestations and diagnosis of enterovirus and parechovirus infections",

section on 'Laboratory diagnosis')

Metapneumovirus (see "Human metapneumovirus infections", section on 'Diagnosis')

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In addition, multiplex tests, which assess the presence of multiple agents at the same time, and PCR­basedtests are becoming more widely available [48].

DIFFERENTIAL DIAGNOSIS — The differential diagnosis of croup includes other causes of stridor and/orrespiratory distress. The primary considerations are those with acute onset, particularly those that may rapidlyprogress to complete upper airway obstruction, and those that require specific therapy. Underlying anatomicanomalies of the upper airway also must be considered, since they may contribute to more severe disease. (See'Host factors' above.)

Important considerations include [1,12]:

Acute epiglottitis – Epiglottitis, which is rare in the era of vaccination against Haemophilus influenzae type b, isdistinguished from croup by the absence of barking cough and the presence of anxiety that is out of proportionto the degree of respiratory distress. Onset of symptoms is rapid, and because of the associated bacteremia, thechild is highly febrile, pale, toxic, and ill­appearing. Because of the swollen epiglottis, the child will have difficultyswallowing and is often drooling. The children usually prefer to sit up and seldom have observed cough [41].Epiglottitis occurs infrequently, and there is no predominant etiologic pathogen. (See "Epiglottitis (supraglottitis):Clinical features and diagnosis".)

Peritonsillar or retropharyngeal abscesses – Children with deep neck space abscesses, cellulitis of thecervical prevertebral tissues, or other painful infections of the oropharynx may present with drooling and neckextension and varying degrees of toxicity. Barking cough is usually absent. (See "Peritonsillar cellulitis andabscess", section on 'Presentation' and "Retropharyngeal infections in children", section on 'Presentation'.)

Foreign body – In foreign body aspiration, there often is a history of the sudden onset of choking and symptomsof upper airway obstruction in a previously healthy child. If an inhaled foreign body lodges in the larynx, it willproduce hoarseness and stridor. If a large foreign body is swallowed, it may lodge in the upper esophagus,resulting in distortion of the adjacent soft extrathoracic trachea, producing a barking cough and inspiratorystridor. (See "Airway foreign bodies in children" and "Foreign bodies of the esophagus and gastrointestinal tractin children".)

Allergic reaction or acute angioneurotic edema – Allergic reaction or acute angioneurotic edema has rapidonset without antecedent cold symptoms or fever. The primary manifestations are swelling of the lips andtongue, urticarial rash, dysphagia without hoarseness, and sometimes inspiratory stridor [1,12]. There may be ahistory of allergy or a previous attack. (See "An overview of angioedema: Clinical features, diagnosis, andmanagement", section on 'Clinical features'.)

Upper airway injury – Injury to the airway from smoke or thermal or chemical burns should be evident from thehistory. The child typically does not have fever or a viral prodrome.

Coronavirus (see "Coronaviruses", section on 'Diagnosis')

Acute epiglottitis

Peritonsillar and retropharyngeal abscesses

Foreign body aspiration or ingestion

Allergic reaction

Acute angioneurotic edema

Upper airway injury

Congenital anomalies of the upper airway

Laryngeal diphtheria (see "Clinical manifestations, diagnosis and treatment of diphtheria")

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Anomalies of the upper airway – Hoarseness and stridor caused by anomalies of the upper airway (eg,laryngeal webs, laryngomalacia, vocal cord paralysis, congenital subglottic stenosis, and subglottichemangioma) and laryngeal papillomas have a more chronic course with absence of fever and symptoms ofupper respiratory tract illness, unless the presentation is due to exacerbation of airway narrowing from theimpact of a concomitant viral infection. (See "Assessment of stridor in children" and "Hoarseness in children:Etiology and management" and "Congenital anomalies of the larynx".)

Other potential mimickers of croup – Other potential mimickers of croup include bronchogenic cyst (whichcan cause airway compression) and early Guillain­Barré syndrome (involvement of the laryngeal nerve maycause vocal cord paralysis) [49,50]. (See "Congenital anomalies of the intrathoracic airways andtracheoesophageal fistula", section on 'Bronchogenic cyst' and "Epidemiology, clinical features, and diagnosis ofGuillain­Barré syndrome in children", section on 'Clinical features' and "Hoarseness in children: Etiology andmanagement", section on 'Vocal fold paralysis'.)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and"Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5 to 6 gradereading level, and they answer the four or five key questions a patient might have about a given condition.These articles are best for patients who want a general overview and who prefer short, easy­to­read materials.Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articlesare written at the 10 to 12 grade reading level and are best for patients who want in­depth information andare comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e­mail thesetopics to your patients. (You can also locate patient education articles on a variety of subjects by searching on"patient info" and the keyword(s) of interest.)

SUMMARY AND RECOMMENDATIONS

th th

th th

Basics topic (see "Patient information: Croup (The Basics)")

Beyond the Basics topic (see "Patient information: Croup in infants and children (Beyond the Basics)")

The term croup has been used to describe a variety of upper respiratory conditions in children, includinglaryngitis, laryngotracheitis, laryngotracheobronchitis, bacterial tracheitis, or spasmodic croup. (See'Definitions' above.)

Croup is usually caused by viruses. Bacterial infection may occur secondarily. Parainfluenza virus type 1 isthe most common cause of croup; other causes include respiratory syncytial virus and influenza virus. (See'Etiology' above.)

Croup most commonly occurs in children 6 to 36 months of age. Most cases occur in the fall or earlywinter. (See 'Epidemiology' above.)

Host factors that may contribute to the development of croup include functional or anatomic susceptibility toupper airway narrowing. (See 'Pathogenesis' above.)

The clinical presentation of croup depends upon the specific croup syndrome and the degree of upperairway obstruction. (See 'Clinical presentation' above.)

The onset of symptoms in laryngotracheitis is gradual, beginning with nasal irritation, congestion, andcoryza. Fever, hoarseness, barking cough, and stridor usually develop during the next 12 to 48 hours.Rapid progression or signs of lower airway involvement suggest a more serious illness. (See'Laryngotracheitis' above.)

The onset of symptoms in spasmodic croup is sudden and always occurs at night. Fever is typicallyabsent, but mild upper respiratory tract symptoms may be present. (See 'Spasmodic croup' above.)

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REFERENCES

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Bacterial tracheitis (picture 1 and image 4) may present acutely or as marked worsening during the courseof an antecedent viral upper respiratory infection. Clinical manifestations of bacterial tracheitis includefever, toxic appearance, and severe respiratory distress. (See 'Bacterial tracheitis' above and "Bacterialtracheitis in children: Clinical features and diagnosis".)

The objectives of the evaluation of the child with croup include assessment of severity and exclusion ofother causes of upper airway obstruction. (See 'Overview' above.)

Rapid assessment of general appearance, vital signs, pulse oximetry, airway stability, and mental statusare necessary to identify children with severe respiratory distress and/or impending respiratory failure. (See'Rapid assessment and initial management' above.)

The history should include a description of the onset, duration and progression of symptoms, and ascertainwhether there are any underlying conditions that predispose to a more severe course. (See 'History'above.)

Aspects of the examination that are useful in assessing the severity of upper airway obstruction includeoverall appearance (including the presence of stridor at rest or only with agitation), quality of voice, work ofbreathing, tidal volume and air entry, and the presence of wheezing. (See 'Examination' above.)

The diagnosis of croup is clinical, based upon the presence of a barking cough and stridor. Neitherradiographs nor laboratory tests are necessary to make the diagnosis. However, radiographs may behelpful in excluding other causes if the diagnosis is in question. (See 'Diagnosis' above.)

The differential diagnosis of croup includes other causes of stridor and/or respiratory distress. The primaryconsiderations are those with acute onset, particularly those that may rapidly progress to complete upperairway obstruction, and those that require specific therapy. Important considerations include acuteepiglottitis, peritonsillar and retropharyngeal abscesses, foreign body aspiration, acute angioneuroticedema, upper airway injury, and congenital anomalies of the upper airway. (See 'Differential diagnosis'above.)

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