Croup - Etiology, Pathology, Clinical Features, Investigations & Treatment
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🗣️ Croup (Acute Laryngotracheobronchitis)
Croup is an acute inflammatory condition involving the larynx, trachea and bronchi.
📌 Also Known As
👉 Acute Laryngotracheobronchitis
⭐ Viral croup is the most common cause of airway obstruction in children. (Important MCQ)
Croup is more common than acute epiglottitis.
Croup may be viral or bacterial.
What is pseudomembranous croup?
Age Group Affected
- Common age group: 6 months to 3 years
- Peak incidence: 2 years
- Annual incidence: 1.5 to 6%.
- More common in winter.
What is the sex prevalence of Croup?
What are the differences between Croup and Acute Epiglottitis?
Etiology of Croup
Viruses
- Parainfluenza virus type 1
- Parainfluenza virus type 2
- Respiratory syncytial virus types A and B
- Rhinovirus
- Metapneumovirus
- Coronavirus
- Bocavirus
Which is the most common organism involved in causing Croup?
Secondary Bacterial Infection
- Streptococcus pyogenes
- Staphylococcus
- Hemolytic streptococci
- Haemophilus influenzae
Pathogenesis of Croup
Viral infection
→ Submucosal edema of the larynx, trachea and bronchi
→ Two levels of obstruction:
| Level of Obstruction | Mechanism | Resulting Feature |
|---|---|---|
| Subglottis | Mechanical obstruction | Inspiratory stridor |
| Tracheobronchial tree | Mechanical and secretional obstruction | Prolonged inspiratory phase with wheeze |
→ Hypoxia and restlessness
→ Cyanosis, hypercapnia and acidosis
→ Stuporous, quiet, glazed facial expression
→ Reduced air entry into the chest and reduced cough reflex
→ Respiratory failure
What are the Pathological Changes seen in Croup?
Why is the Subglottic Area crucial in Croup?
What are the differences between the adult and pediatric larynx?
Clinical Features of Croup
Symptoms of Croup
⭐ Symptoms occur because of mucosal edema of the larynx and trachea following the viral illness.
- Preceding History of Upper respiratory tract infection
- Hoarseness of voice
- Brassy, barking croupy cough
- Difficulty in breathing
- Throat pain
What is the term used to describe the cough seen in Croup patients?
Which symptom helps in differentiating a case of Acute Epiglottitis from a case of Croup?
What are the factors which predispose to severe symptoms in Croup?
Signs of Croup
- Child is restless and anxious
- ❌ Child is usually not toxic
- May or may not be febrile
- Inspiratory or biphasic stridor
What are the signs of Respiratory Failure in severe cases of Croup?
What are the Complications of Croup?
⭐ Westley Croup Score
A scoring system based on five clinical features of croup.
👉 The total score correlates with the diameter of the tracheal lumen.
⭐ Maximum score: 17
| Clinical Feature | Finding | Score |
|---|---|---|
| Inspiratory stridor | None | 0 |
| Audible with a stethoscope | 1 | |
| Audible without a stethoscope | 2 | |
| Retraction | None | 0 |
| Mild | 1 | |
| Moderate | 2 | |
| Severe | 3 | |
| Air entry | Normal | 0 |
| Decreased | 1 | |
| Severely decreased | 2 | |
| Cyanosis | None | 0 |
| With agitation | 4 | |
| At rest | 5 | |
| Level of consciousness | Normal | 0 |
| Altered | 5 |
How will you classify the severity of Croup based on Westley Croup Score?
Investigations of Croup
⭐ Croup is primarily a clinical diagnosis, made from the history and clinical features. Investigations are needed only in severe cases or when there is a diagnostic dilemma.
1- X-ray Thoracic Inlet / Neck (Anteroposterior View)
👉 Steeple Sign, also known as the Pencil Tip Sign
Narrowing of the subglottis produces an appearance resembling a pencil tip or the steeple of a church.
What are the signs seen in Croup and Acute Epiglottitis?
2- Flexible Fibreoptic Laryngoscopy
⚠️ Performed only in the operation theatre, ready for intubation if necessary.
What are the findings seen in Flexible Fibreoptic Laryngoscopy in Croup?
3- X-ray Chest
To rule out:
- Basal collapse
- Mediastinal shift
- Emphysema
- Foreign body
- Pulmonary edema
4- HRCT Neck and Mediastinum
When is HRCT Neck and Mediastinum indicated in croup?
Treatment of Croup
⭐ Croup is a self-limiting disease.
- About 50% of children improve within 24 hours of onset of symptoms
- Most recover within 4 days, even without treatment
- Rarely, airway symptoms become serious and life-threatening
👉 Mild cases need only supportive treatment, with reassurance of the child and caregiver, and monitoring of symptoms.
1- Hospitalization
The patient is kept under observation for worsening symptoms and impending airway obstruction.
2- Oxygen
Given at a flow rate of 3 to 5 litres per minute.
3- Humidification of Inspired Air
👉 Softens the thick tenacious secretions and crusts obstructing the airway.
4- IV Fluids
To combat dehydration.
5- Corticosteroids (Mainstay of Treatment)
What is the Mechanism of Action of corticosteroids in treatment of Croup?
Which corticosteroids are used to treat Croup, and what are their doses?
⭐ Clinical benefit is assessed by improvement in the Westley Croup Score.
6- Nebulized Epinephrine
- Provides only short symptomatic relief, with no lasting effect beyond about 2 hours
- Does not alter the natural course of the disease
- Only postpones or eliminates the need for an artificial airway such as intubation or tracheostomy
- Usually given at the same time as glucocorticoids
What is the dosage of Nebulized Epinephrine in treatment of Croup?
What is the Mechanism of Action of Nebulized Epinephrine in treatment of Croup?
7- Heliox
What is Heliox?
What is the Mechanism of Action of Heliox in treatment of Croup?
⚠️ Disadvantage
High thermal conductivity, so humidification must be used to avoid hypothermia.
8- Broad Spectrum Antibiotics
Given if there is a secondary bacterial infection.
9- Intubation and Tracheostomy
Required only in rare cases of airway obstruction.
What are the Indications for Intubation in Croup?
What are the Criteria for Extubation in Croup?
Tracheostomy
⭐ A last-ditch measure, preferred only when intubation is expected to be needed for longer than 72 hours.
What is the Differential Diagnosis of Croup?
🦠 Bacterial Laryngotracheobronchitis
A severe form of laryngotracheobronchitis, characterized by profuse mucopurulent secretions with sloughing of the respiratory epithelium.
⭐ Rare but potentially life threatening cause of upper airway obstruction in children.
What are the other names of Bacterial Laryngotracheobronchitis?
Etiology of Bacterial Laryngotracheobronchitis
- Staphylococcus aureus
- Haemophilus influenzae
- Moraxella catarrhalis
- Pneumococcus
- Pseudomonas aeruginosa
What are the Clinical Features of Bacterial Laryngotracheobronchitis? How is it different from Viral Laryngotracheobronchitis?
Diagnosis of Bacterial Laryngotracheobronchitis
⭐ Requires a high index of suspicion for early diagnosis.
What are the findings seen on endoscopy of the larynx in a case of Bacterial Laryngotracheobronchitis?
⭐ It is often necessary to secure the airway by intubation for a couple of days.
Treatment of Bacterial Laryngotracheobronchitis
- IV broad spectrum antibiotics (mainstay)
- Repeated therapeutic tracheobronchoscopy to clear secretions
What are the Complications of Bacterial Laryngotracheobronchitis?
🧠 Viva Pearls
- Croup is also known as acute laryngotracheobronchitis.
- Viral croup is the most common cause of airway obstruction in children.
- Common age group is 6 months to 3 years, with a peak at 2 years.
- The child in croup is not toxic, unlike in acute epiglottitis.
- Stridor in croup is inspiratory or biphasic.
- Westley Croup Score uses five clinical features, with a maximum score of 17.
- Steeple sign or pencil tip sign is seen on an AP X-ray of the neck.
- Croup is a self-limiting disease, with most children recovering within 4 days.
- Corticosteroids are the mainstay of treatment.
- Intramuscular dexamethasone is avoided due to the risk of muscle necrosis.
- Nebulized epinephrine gives only short symptomatic relief and does not alter the course of the disease.
- Tracheostomy is preferred only when intubation is expected for longer than 72 hours.
- Pseudomembranous croup is the bacterial form, affecting older children aged 4 to 8 years.
- Pseudomembranous croup fails to respond to steroids and nebulized epinephrine.
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