Cough is one of the most common reasons for doctors office visits in pediatrics. The majority of the cases are due to an acute respiratory infection such as the common cold or acute bronchitis, but there are some patients who have a chronic cough lasting longer than 3 weeks. Many of these patients are otherwise healthy.

The cough is a part of the respiratory defense mechanism and plays a major role in a broncho-pulmonary clearance, especially when the clearance mechanism is stressed by mucosal swelling, bronchospasm and increased secretion. Another significant role the cough plays is as a signal that something is wrong with the respiratory tract. Physicians will work with the patient and family to determine how serious the cough is and take appropriate action. In various disease states such as viral respiratory infections and bronchial asthma, the removal of the secretion is adversely affected in two ways. First, ventilatory capacity is generally diminished in these diseases and the speed of airflow through the airways at the time of cough would be decreased, making the cough less effective. Second, the mucociliary apparatus does not function well.

The cough is important for our health. However, when a child coughs daily for longer than 3 to 4 weeks, you should consult your child's physician, even if he/she is otherwise healthy. Research has indicated that chronic cough (in more than half of all adult patients) can be a sole manifestation of asthma and asthma/sinusitis/postnasal drip. It is believed by many pediatric pulmonologists that the same is true in children. Therefore, it is now a common medical practice to first try asthma medicines for chronic cough, without extensive diagnostic tests, especially if chest x-rays are negative. If asthma medicines are not effective, the physician may prescribe medicines for sinusitis/postnasal drip.

If the child still coughs after the above-mentioned trial treatment for a few to several weeks, doctors begin a diagnostic work-up for other causes that are not as common. The differential diagnosis would include the following five categories:

1. bronchitis
2. suppurative lung disease
3. focal lesions of the larynx and tracheal bronchial tree
4. psychogenic cough
5. post-nasal drip

In bronchitis, there are infectious, allergic and chemical causes. Suppurative lung disease includes cystic fibrosis, bronchiectasis, chronic atelectasis, retained foreign body, and congenital malformation. In the focal lesions of the airways, there is foreign body aspiration, mediastinal or pulmonary tumors, cysts, and glands, bronchial and tracheal stenosis, cysts and hemangiomas. As in pneumonias, the patient’s age can help in arriving at the appropriate diagnosis. In infancy, the main causes are: congenital malformations, congenital infections, aspiration and cystic fibrosis. Inhaled foreign body, suppurative lung disease and bronchitis associated with chronic upper respiratory tract disease are seen in pre-school (age 1 to 5 years) children. When we move up to the school age (5 to 15 years), cigarette smoking, m. pneumoniae infection and psychogenic cough are the main causes. Common to all age groups include recurrent viral bronchitis, asthma and pertussis.

History and physical examination are the most important parts of the diagnostic work-up. In fact, some cases can be diagnosed by detailed history and physical examination alone, and even in the cases where the diagnosis is not clear at first. When further diagnostic work-up is necessary, one or more of the following studies are done depending on the circumstances:

• CBC
• chest x-rays
• serum immunoglobulins
• serum IgE
• RAST
• sweat test
• esophogogram and
• bronchoscopy

In older patients, one can get a sputum examination for bacterial study and eosinophils. Serum IgE, RAST and allergy skin tests can be helpful when one suspects allergy as the cause of the chronic cough.  Esophogogram is done for mediastinal lesions, and UGI for gastro-esophageal reflux. When aspiration is suspected, a dysphagia study is used and a foreign body is suspected, rigid bronchoscopy is indicated. In some cases where no cause is found after extensive non-invasive work-up, bronchoscopy can be helpful.

After the diagnosis is established, of course, appropriate therapy is instituted. For example, antibiotics will be necessary for infections, and anti-reflux therapy GER if the reflux is causing the chronic cough. If the patient turns out to have cystic fibrosis, she or he should be on an appropriate program for cystic fibrosis. Chronic cough in children is generally due to non-life threatening diseases in more than half of the cases, but can be the beginning of a serious ailment.

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