Bronchiolitis overview

Jump to navigation Jump to search


Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Ahmed Elsaiey, MBBCH [2]

Bronchiolitis Microchapters

Home

Patient Information

Overview

Historical Perspective

Classification

Pathophysiology

Causes

Differentiating Bronchiolitis from other Diseases

Epidemiology and Demographics

Risk Factors

Screening

Natural History, Complications and Prognosis

Severity Score

Diagnosis

History and Symptoms

Physical Examination

Laboratory Findings

X Ray

CT scan

MRI

Other Imaging Findings

Other Diagnostic Studies

Treatment

Medical Therapy

Surgery

Primary Prevention

Secondary Prevention

Cost-Effectiveness of Therapy

Future or Investigational Therapies

Case Studies

Case #1

Bronchiolitis overview On the Web

Most recent articles

Most cited articles

Review articles

CME Programs

Powerpoint slides

Images

American Roentgen Ray Society Images of Bronchiolitis overview

All Images
X-rays
Echo & Ultrasound
CT Images
MRI

Ongoing Trials at Clinical Trials.gov

US National Guidelines Clearinghouse

NICE Guidance

FDA on Bronchiolitis overview

CDC on Bronchiolitis overview

Bronchiolitis overview in the news

Blogs on Bronchiolitis overview

Directions to Hospitals Treating Bronchiolitis

Risk calculators and risk factors for Bronchiolitis overview

Overview

Bronchiolitis is the most common lower respiratory tract infection in pediatric patients between 1 month and 2 years of age. It is usually caused by the respiratory syncytial virus (RSV) and is characterized by inflammation, edema, and necrosis of the bronchiole's epithelium. It is classified according to histological features as bronchiolitis obliterans, proliferative bronchiolitis, diffuse panbronchiolitis, or respiratory bronchiolitis. The bronchiolitis severity score is used to classify bronchiolitis into 4 classes. Typical clinical manifestations include rhinitis, cough, wheezing, respiratory rales (crackles), use of respiratory accessory muscles, and/or nasal flaring. In adults, common risk factors in the development of bronchiolitis include exposure to cigarette smoke, living in crowded areas, and being immunocompromised. In infants, the risk factors include age < 6 months, lack of breastfeeding, prematurity, and having congenital heart diseases. The mainstay of treatment of bronchiolitis is supportive therapy.

Historical Perspective

Bronchiolitis was first reported in 1899 when it was discovered by researchers at the University of Minnesota. The disease was fully described in 1901 by Dr. Lange.

Classification

Bronchiolitis should be classified in order to understand how it may occur and the clinical manifestations that may be observed. Bronchiolitis is classified based on the patient's age and the different histological forms of the disease. According to age, bronchiolitis is classified as either adult or infant. Based on the different histological features, it can be classified as acute infectious bronchiolitis, bronchiolitis obliterans, proliferative bronchiolitis, diffuse panbronchiolitis, or respiratory bronchiolitis. Based on the Bronchiolitis Severity Score (BSS), bronchiolitis is classified into 4 classes.

Pathophysiology

Bronchiolitis is transmitted by air droplets. It is caused by RSV, which infects the nasopharyngeal mucosa. After the infection, the virus spreads to the lower airway tracts until it reaches the bronchioles, where viral replication takes place. The viral infection induces inflammation, which leads to edema and necrosis of the bronchiolar epithelium. Cough reflex occurs due to exposure of the subepithelial tissue and nerve fibers. Vascular permeability increases, leading to edema and swelling. Histopathologically, bronchiolitis obliterans shows intraluminal polyps, inflammatory infiltration, and macrophages. Constrictive bronchiolitis shows thickening of the airways and interluminal narrowing.

Causes

Bronchiolitis usually affects children under the age of 2, with a peak age of 3 - 6 months. Bronchiolitis is a common disease in children and sometimes causes severe illness. Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis. Other viruses that can cause bronchiolitis include adenovirus, influenza, and parainfluenza. It may be caused by bacterial organisms like Legionella pneumophilia and Mycoplasma pneumonia. Other noninfectious causes include smoking, collagen vascular disease, and being post bone marrow transplant.

Differentiating Bronchiolitis from Other Diseases

Bronchiolitis must be differentiated from other respiratory and cardiac diseases that present with similar clinical manifestations. Based on cough and dyspnea, bronchiolitis should be differentiated from asthma, COPD, pneumonia, congestive heart failure, diffuse idiopathic neuroendocrine cell hyperplasia, tuberculosis, pertussis, foreign body aspiration, pulmonary embolism, and Harman-Rich syndrome.

Epidemiology and Demographics

Bronchiolitis is one of the most common acute respiratory diseases that affects infants and children. Bronchiolitis affects around 3,000 per 100,000 children in the United States. It occurs mostly during fall, winter, and early spring. Bronchiolitis can affect any age group, but mostly affects infants, especially those under 2 years. Bronchiolitis occurs more often in boys than girls and is more common among Native Americans, Alaskans, and Hispanics. Bronchiolitis has a low mortality rate despite the high number of hospitalizations associated with the illness.

Risk Factors

Bronchiolitis has a different range of risk factors that can be differentiated based on the age. In adults, common risk factors in the development of bronchiolitis include exposure to cigarette smoke, living in crowded areas, and being immunocompromised. In infants, the risk factors include age < 6 months, lack of breastfeeding, prematurity, and having congenital heart diseases.

Natural History, Complications, and Prognosis

If left untreated, in the first 2-3 days, a patient with bronchiolitis presents with mild upper respiratory symptoms, shortness of breath, wheezing, persistent prominent cough, and tachypnea. Chest wall retraction and nasal flaring usually develop between the third and seventh day. Symptoms gradually disappear within the next 2 weeks. Complications are usually observed among patients younger than 2 months of age, premature infants, and patients with other medical conditions (congenital heart disease, chronic pulmonary disease, and immunodeficiencies). Severity scores can be used to estimate the prognosis.

Diagnosis

History and Symptoms

Common symptoms of bronchiolitis include fevercoughdyspnea, and Nasal discharge. Other symptoms include post tussive vomiting and dehydration.

Physical Examination

Patients infected with bronchiolitis have a toxic appearance and may be cyanotic. Fever is one of the signs of the disease, but a lack of it does not exclude the diagnosis. Lung examination shows abnormalities in inspection and auscultation. On inspection, intercostal and substernal retractions can be observed. On auscultation, wheezing and crackles can be clearly heard with a decrease in respiratory sounds. Extrapulmonary manifestations can occur as well, including pharyngitis, conjunctivitis, arrhythmias, tachycardia, and seizures.

Laboratory Findings

Bronchiolitis diagnosis depends mainly on the symptoms and physical examination, as the laboratory diagnosis is not specific for the disease. Commonly used lab tests include viral pathogen tests like ELISA, immunofluorescent assays, and optical immunoassays. Complete blood count is also not specific for bronchiolitis. Pulmonary function tests may be helpful in supporting the diagnosis and excluding other obstructive lung diseases.

X-ray

Chest X-ray in cases of bronchiolitis is usually nonspecific and may be inefficient for differentiating bronchiolitis from other lower respiratory tract infections. A chest X-ray may show atelectasis and consolidations. It is also used in excluding other medical conditions like pneumonia.

CT

CT scan shows nonspecific findings that can be found in other diseases. These findings are centrilobular nodules, bronchiolar wall thickening, ground glass appearance, and parenchymal cysts.

MRI

There are no MRI findings associated with bronchiolitis.

Other Imaging Findings

There are no additional imaging findings for bronchiolitis.

Other Diagnostic Studies

There are no additional diagnostic findings for bronchiolitis.

Treatment

Medical Therapy

The predominant therapy for bronchiolitis is providing supportive measures. Supportive therapy includes frequent, small feeding and oxygen therapy. In severe cases, infants may require intravenous fluids and food via a nasogastric tube. In extreme cases, mechanical ventilation or the use of continuous positive airway pressure (CPAP) might be necessary. Prophylaxis is indicated in infants with hemodynamically significant heart disease and preterm infants who require >21% oxygen for at least the first 28 days of life. The drug of choice for prophylaxis is palivizumab.

Surgery

Surgical intervention is not recommended for the management of bronchiolitis.

Primary Prevention

Effective measures for the primary prevention of bronchiolitis include washing hands, avoiding contact with patients with symptomatic respiratory infections, and prevention of tobacco smoke exposure. These preventive measures are to prevent viral dissemination during the RSV season. In patients with a high risk of developing severe infection, passive immunization with palivizumab is recommended.

Secondary Prevention

There are no secondary preventive measures available for bronchiolitis.

References


Template:WikiDoc Sources