Chronic cough
Cough is a common symptom in patients presenting to the clinic, and according to statistics, more than 80% of patients presenting to the respiratory clinic have coughing symptoms. Coughing is a protective reflex to remove excess secretions from the airway or to prevent foreign substances from entering the airway. However, if the cough does not stop and becomes acute to chronic, it often causes great pain to the patient. A cough of more than three weeks is called a chronic cough. Chronic cough is often not clearly defined and is often considered to be an infection (e.g. bronchitis) and is treated with antibacterial drugs for a long time, resulting in a waste of drug resources and damage to health.
Chronic cough can be divided into two main groups according to its etiology.
One category is chronic cough caused by various underlying lung diseases, such as chronic obstructive pulmonary disease, bronchiectasis, tracheo-bronchial carcinoma, diffuse interstitial lung disease, immune and vascular inflammatory diseases, etc. Abnormalities can be detected by performing routine chest imaging (chest radiograph or chest CT).
The other type of cough is chronic cough with no obvious underlying lung pathology and normal conventional chest imaging, which has more complex causes and is more likely to be misdiagnosed and missed. The most common causes are the following.
I. Cough variant asthma.
A specific type of asthma in which cough is the only clinical manifestation, without obvious symptoms such as wheezing and shortness of breath, but with airway hyperresponsiveness. It often manifests as an irritating dry cough, coughing at night, easily induced or aggravated by cold, cold air, dust and oil fumes, often seasonal (in northern regions), and often accompanied by other allergic diseases such as allergic rhinitis.
II. Postnasal drip syndrome (rhinitis/sinusitis).
Due to diseases of the nasopharynx and laryngopharynx causing more secretions to adhere to the postnasal and laryngopharyngeal areas and even backflow into the vocal cords or trachea leading to coughing. There is often a history of rhinitis, sinusitis, nasal polyps, chronic pharyngitis, etc., episodic or persistent cough, mainly during the daytime, less often waking up after sleep due to coughing, with postnasal drip and/or a feeling of mucus adhesion to the posterior pharyngeal wall
III. Gastroesophageal reflux cough.
It is caused by reflux of stomach acid and other gastric contents into the esophagus resulting in symptoms or complications in the body. If coughing is the prominent symptom, it is called GERD cough. Typical reflux symptoms: heartburn, acid reflux, belching, chest tightness, and cough can be its only clinical manifestation.
IV. Eosinophilic bronchitis.
Non-asthmatic bronchitis characterized by increased eosinophil infiltration, accounting for about 10 to 22% of chronic coughs, mainly characterized by a chronic irritating dry cough with occasional sputum, the only symptom in most patients, some patients are sensitive to fumes, dust, odors or cold air, which can be a triggering factor, without wheezing and dyspnea, induced sputum eosinophils ≥ 3%, effective with oral or inhaled glucocorticoid therapy .
V. Drug-induced cough.
Nowadays, commonly used antihypertensive drugs such as captopril, enalapril, cilazapril, betalactam, etc., usually reduce or disappear the cough significantly after 4 weeks of discontinuation.
VI. Psychogenic cough.
Caused by serious psychological problems or intentional throat clearing by the patient, it is also known as habitual cough. Psychogenic cough is relatively common in pediatric patients. The cough is present during the daytime and not at night, often with symptoms of anxiety. The cough disappears when focusing on something and at night rest, accompanied by barking or goose calls.
VII. Atypical pulmonary lesions.
For example, mild bronchiectasis without hemoptysis or pus sputum, or even chest X-ray or CT, may manifest as chronic cough; lung tumors, which are small and neglected, may first manifest as persistent cough; endobronchial tuberculosis with inconspicuous intrapulmonary lesions and a dry cough drama; smoking, exposure to dust, occupational dust, and occupational allergies may cause chronic cough and must be excluded; heart failure may first be dominated by cough symptoms, especially if heart failure When symptoms are not obvious; patients with foreign bodies in the airways and goiter can have cough symptoms.
In summary For chronic cough without clear underlying lung pathology, medical history, including ear, nose and throat and gastrointestinal examinations, should be taken seriously, from simple to complex, with common diseases first, followed by rare diseases, and when conditions are not available, diagnostic treatment should be carried out according to clinical features, and the cause of cough should be determined according to the response to treatment. However, as an empirical treatment, if the dosage is appropriate and the clinical effect is not obvious, ciliofibroscopy should be performed at the right time, instead of increasing the dosage and waiting for follow-up to avoid delaying the diagnosis of certain diseases, such as endobronchial tuberculosis, bronchial cancer or polyps, and endotracheal foreign bodies. Usually, after a thorough etiologic examination, including rare causes, there may still be a proportion (≤30%) of patients with cough of unknown etiology. During empirical symptomatic treatment, careful observation and examination should still be performed to avoid missed diagnoses and misdiagnosis.