CHRONIC COUGH

12 CHRONIC COUGH

General Discussion

The cough reflex is complex, but cough generally results from irritant stimulation of one or more receptors in the respiratory system. Estimating the duration of cough is the first step in narrowing the list of possible diagnoses. Cough may be classified as acute (less than 3 weeks), subacute (3–8 weeks), or chronic (more than 8 weeks). If the cough is productive of blood, the patient should be evaluated according to guidelines for hemoptysis.

In non-smokers who do not take an ACE inhibitor and whose chest X-ray is normal, the most likely causes of chronic cough are asthma, postnasal drip, or gastroesophageal reflux disease (GERD). Other common causes in immunocompetent patients include chronic bronchitis due to cigarette smoking or other irritants, bronchiectasis, and eosinophilic bronchitis. The physician should assess the likelihood of the most common causes by means of trials of empirical therapy and trials involving the avoidance of irritants and drugs, along with focused laboratory testing such as chest radiography or methacholine challenge.

A normal chest radiograph in an immunocompetent patient makes postnasal drip syndrome, asthma, GERD, chronic bronchitis, and eosinophilic bronchitis more likely and bronchogenic carcinoma, tuberculosis, bronchiectasis, and sarcoidosis unlikely. If the chest radiograph is abnormal, the patient should be evaluated on the basis of the diseases suggested by the radiographic findings.

Postnasal drip syndrome is the most common cause of chronic cough and no diagnostic test exists, so the patient should be evaluated for this condition first. Next, asthma may be considered as a cause of chronic cough. A methacholine challenge should be considered since its negative predictive value is 100%. For the consideration of GERD, 24-hour monitoring of the esophagus is not routinely recommended because it is inconvenient for patients, is not widely available, and lacks sensitivity and specificity.

Although most chronic smokers have a cough, it should not be assumed that the cough is due to the smoking unless smoking ceases and the cough resolves. It is also important to recognize that multiple conditions often simultaneously contribute to cough. The definitive diagnosis of the cause of chronic cough is established on the basis of an observation of which specific therapy eliminates the cough. A chronic cough may be due to more than one condition 18 to 93% of the time, so therapy that is partially successful should not be stopped but should instead be sequentially supplemented.

If the patient has a history of smoking, is exposed to environmental irritants, or is currently being treated with an ACE inhibitor, the patient should be instructed to eliminate the irritant or discontinue the medication for 4 weeks. If the cough improves or resolves, the cough is partially or entirely due to chronic bronchitis or to the ACE inhibitor.

Eosinophilic bronchitis can be distinguished from asthma by the lack of bronchial hyperresponsiveness or variable airflow obstruction. Eosinophilic bronchitis should be considered in patients with negative methacholine challenge tests. It can be ruled out as a cause of chronic cough if eosinophils make up less than 3% of the nonsquamous cells in a sample of induced sputum.

Tuberculosis (TB) should be considered early in the evaluation of patients with chronic cough when the likelihood of tuberculosis is high. This includes areas where the prevalence of TB is high and in populations at high risk of TB such as HIV-infected persons. TB should also be considered in patients with chronic cough who have sputum production, hemoptysis, fever, or weight loss.

Tags: Instant Work-ups A Clinical Guide to Medicine

Aug 17, 2016 | Posted by admin in PEDIATRICS | Comments Off

Full access? Get Clinical Tree

Get Clinical Tree app for offline access

Get Clinical Tree app for offline access