Bronchiolitis
Classification & external resources

ICD-10	J21.
ICD-9	466.1
DiseasesDB	1701
MedlinePlus	000975
eMedicine	emerg/365
MeSH	D001988

Bronchiolitis is inflammation of the bronchioles, the smallest air passages of the lungs.

Causes

The term usually refers to acute viral bronchiolitis, a common disease in infancy. This is most commonly caused by respiratory syncytial virus (RSV, also known as human pneumovirus). (J21.0)

Other viruses which may cause this illness include metapneumovirus, influenza, parainfluenza, coronavirus, adenovirus, and rhinovirus.

The American Academy of Pediatrics has published a clinical practice guideline for the Diagnosis and Management of Bronchiolitis, including a review of the evidence and recommendations.

Presentation

In a typical case, an infant under twelve months of age develops cough, wheeze, and shortness of breath over one or two days. The diagnosis is made by clinical examination. Chest X-ray is sometimes useful to exclude pneumonia, but not indicated in routine cases.

Testing for specific viral cause (e.g. RSV by nasopharyngeal aspirate) is common, but has little effect on management. Identification of RSV-positive patients can be helpful for:

*disease surveillance

*grouping ("cohorting") patients together in hospital wards as to prevent cross infection

*predicting whether the disease course has peaked yet

*reducing the need for other diagnostic procedures (by providing confidence that a cause has been identified).

The infant may be breathless for several days. After the acute illness, it is common for the airways to remain sensitive for several weeks, leading to recurrent cough and wheeze. (There is a possible link with later asthma: possible explanations are that bronchiolitis causes asthma by inducing long term inflammation, or that children who are destined to be asthmatic are more susceptible to develop bronchiolitis.)

Treatment

There is no effective specific treatment for bronchiolitis. Therapy is principally supportive. Infants who are too short of breath to feed may require nasogastric or intravenous fluids. Oxygen may be required to maintain blood oxygen levels, and in severe cases the infant may need mechanical ventilation.

Bronchodilator drugs such as salbutamol/albuterol are no longer considered recommended, but many clinicians offer a trial dose to see if there is any benefit (especially if there is a family history of asthma, since it can be difficult to distinguish bronchiolitis from a first-ever asthma exacerbation). Racemic epinephrine is another drug that is also frequently used.

Ribavirin is an antiviral drug which has some effect in RSV infection, but it is reserved for infants with pre-existing lung, heart or immune disease. Antibiotics are often given in case of bacterial superinfection, but have no effect on the underlying viral infection.

The use of hypertonic saline is also growing in bronchiolitis. Initially recommended for use in cystic fibrosis patients, it is thought to increase hydration of secretions, thus facilitating their removal.

Prevention

In general, prevention of bronchiolitis relies on measures to reduce the spread of the viruses that cause respiratory infections (that is, handwashing, and avoiding exposure to those symptomatic with respiratory infections).

Premature infants, and others with certain majory cardiac and respiratory disorders, can receive passive immunization with Palivizumab (a monoclonal antibody against RSV). The use of this immunization requires yearly immunization every month during the winter, also only to high-risk infants.

•  • [ e] Pathology of respiratory system (, )
Acute upper respiratory infections	Upper respiratory tract infection Common cold Rhinitis Sinusitis Pharyngitis (Strep throat) Tonsillitis Laryngitis Tracheitis Croup Epiglottitis
Influenza and Pneumonia	Influenza Pneumonia (Viral, Bacterial, Bronchopneumonia)
Other acute lower respiratory infections	Bronchitis Bronchiolitis
Other diseases of upper respiratory tract	Vasomotor rhinitis Hay fever Atrophic rhinitis Nasal polyp Adenoid hypertrophy Peritonsillar abscess Vocal fold nodule Laryngospasm
Chronic lower respiratory diseases	Emphysema COPD Asthma Status asthmaticus Bronchiectasis
Lung diseases due to external agents	Pneumoconiosis (Coalworker's pneumoconiosis, Asbestosis, Silicosis, Bauxite fibrosis, Berylliosis, Siderosis) Byssinosis Hypersensitivity pneumonitis (Farmer's lung, Bird fancier's lung)
Other, principally affecting the interstitium	Acute respiratory distress syndrome Pulmonary edema Hamman-Rich syndrome Interstitial lung disease
Suppurative and necrotic conditions of lower respiratory tract	Lung abscess Pleural effusion Empyema
Other	Pneumothorax Hemothorax Hemopneumothorax Mendelson's syndrome Respiratory failure Atelectasis Mediastinal emphysema Mediastinitis
see also (, )