A detailed history
frequently provides
the most valuable clues for etiology of the cough. Particularly important
questions include:
1.
Is
the cough acute or chronic?
2.
At
its onset, were there associated symptoms suggestive of a respiratory
infection?
3.
Is
it seasonal or associated with wheezing?
4.
Is
it associated with symptoms suggestive of postnasal drip (nasal discharge,
frequent throat clearing, a “tickle in the throat”) or gastroesophageal reflux
(heartburn or sensation of regurgitation)? (The absence of such suggestive
symptoms does not exclude either of these diagnoses, particularly in the case
of gastroesophageal reflux.)
5.
Is
it associated with fever or sputum? If sputum is present, what is its
character?
6.
Does
the patient have any associated diseases or risk factors for disease (e.g.,
cigarette smoking, risk factors for infection with HIV, environmental
exposures)?
7.
Is
the patient taking an ACE inhibitor?
The general physical
examination may
point to a systemic or nonpulmonary cause of cough, such as heart failure,
primary nonpulmonary neoplasm, or AIDS. Examination of the oropharynx may
provide suggestive evidence for postnasal drip, including oropharyngeal mucus
or erythema, or a “cobblestone” appearance to the mucosa. Auscultation of the
chest may demonstrate inspiratory stridor (indicative of upper airway disease),
rhonchi or expiratory wheezing (indicative of lower airway disease), or
inspiratory crackles (suggestive of a process involving the pulmonary
parenchyma, such as interstitial lung disease, pneumonia, or pulmonary edema).
Chest radiography may be particularly helpful in suggesting or confirming the
cause of the cough. Important potential findings include the presence of an
intrathoracic mass lesion, a localized pulmonary parenchymal infiltrate, or
diffuse interstitial or alveolar disease. An area of honeycombing or cyst
formation may suggest bronchiectasis, while symmetric bilateral hilar
adenopathy may suggest sarcoidosis.
Pulmonary function testing (Chap. 234) is useful for assessing the functional
abnormalities that accompany certain disorders producing cough. Measurement of
forced expiratory flow rates can demonstrate reversible airflow obstruction
characteristic of asthma. When asthma is considered but flow rates are normal,
bronchoprovocation testing with methacholine or cold-air inhalation can demonstrate
hyperreactivity of the airways to a bronchoconstrictive stimulus. Measurement
of lung volumes and diffusing capacity is useful primarily for demonstration of
a restrictive pattern, often seen with any of the diffuse interstitial lung
diseases.
If sputum
is produced, gross
and microscopic examination may provide useful information. Purulent sputum
suggests chronic bronchitis, bronchiectasis, pneumonia, or lung abscess. Blood
in the sputum may be seen in the same disorders, but its presence also raises
the question of an endobronchial tumor. Greater than 3% eosinophils seen on
staining of induced sputum in a patient without asthma suggests the possibility
of eosinophilic bronchitis. Gram and acid-fast stains and cultures may
demonstrate a particular infectious pathogen,
while sputum cytology may provide a diagnosis of a pulmonary malignancy.
More specialized studies
are helpful in specific circumstances. Fiberoptic bronchoscopy is the procedure of choice for
visualizing an endobronchial tumor and collecting cytologic and histologic specimens.
Inspection of the tracheobronchial mucosa can demonstrate endobronchial
granulomas often seen in sarcoidosis, and endobronchial biopsy of such lesions
or transbronchial biopsy of the lung interstitium can confirm the diagnosis.
Inspection of the airway mucosa by bronchoscopy can also demonstrate the
characteristic appearance of endobronchial Kaposi’s sarcoma in patients with
AIDS. High-resolution computed tomography (HRCT) can confirm the presence of
interstitial disease and frequently suggests a diagnosis based on the pattern
of disease. It is the procedure of choice for demonstrating dilated airways and
confirming the diagnosis of bronchiectasis.
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