Cough is a common symptom, and almost everyone has experienced it. Cough is an important symptom of common cold, flu or other common upper respiratory infections but it usually subsides within 1-3 weeks. Doctors divide cough according to he duration of cough as follow:
- Acute Cough – lasts 3 weeks or less
- Chronic Cough – lasts more than 3 weeks
Most causes of acute cough are related to infections, important among them are common cold, influenza, acute sinus infection, and acute bronchitis. Among the important causes which one need to be aware of are:
- Occasionally patient may have whooping cough which is not always easy to diagnose, but diagnosis is critical as early treatment can help reduce complications, and prevent the spread to others.
- Pneumonia: bacterial pneumonia, walking pneumonia can start with minor respiratory infection, but can make a person very sick. If you have shortness of breath, chest pain and/or fever, suspect something wrong with your lungs and have your healthcare provider examine the patient and possibly do x-rays.
- Acute Asthma especially cough variant asthma can present with lot of cough, which may be confused for acute bronchitis or cough due to respiratory infection.
Cough persisting for more than 3 weeks may be due to any of myriad conditions originating in nose, sinus, throat, larynotracheobronchial tree, lung parenchyma, heart, and esophagus. Deciphering the cause of cough requires a thorough history, examination and necessary testing depending on the history and examination findings.
- Smoking is one of the most important cause of cough, even in patients who do not have COPD.
- ACE inhibitors: these medications are used to treat patients with high blood pressure. 5-10% patients develop cough within six months after starting ACE inhibitors. Occasionally cough following ACE inhibitors may start years after patient start taking ACE inhibitors.
- Those patients who are not smokers, and have normal chest x-ray, following three conditions account for more than 90% of the cases:
- Upper airway cough syndrome: it was previously called post nasal drip. It account for more than 60% of the patients with chronic cough. Half of the patients have underlying allergies and other half are due to non-allergic rhinitis, chronic sinusitis or other causes of nasal and sinus diseases. Many patients with infectious sinusitis are misdiagnosed as allergic nasal disease and treated for allergic nasal disease.
- Cough variant asthma: asthma or cough variant account for 20-30% of the patients with chronic cough. It is easier to diagnose patients with asthma when they exhibit usual symptoms of wheezing, cough, chest tightness and shortness of breath. Normal breathing test (PFT) does not rule out asthma. Patient may need to undergo methacholine challenge test to rule out asthma. Sometimes, a trial of asthma medications may help resolve the issue.
- Gastro esophageal reflux disease: When the content of stomach acid backs up in esophagus, it is called gastro esophageal reflux (GERD). Most patients with reflux experience heartburn, but many do not. Many patients with reflux experience throat clearing, feel like lump in the throat, hoarseness, chest tightness and are diagnosed with repeated bronchitis, asthma, and chronic cough. These symptoms can worsen asthma. Those with predominant throat or laryngeal symptoms are called to have laryngopharyngeal reflux (LPR). GERD or LPR account for 20-30% of cases of chronic cough.
- It is not uncommon to see patients have upper airway cough syndrome with asthma and GERD in various combinations. It is important to figure out the various components of this puzzle.
- Postinfection cough: Many time a patient has cough which persists for more than three weeks following a viral disease. These patients don’t have whooping cough, sinusitis, asthma, reflux or pneumonia. This is due to persistent inflammation after the infection and will eventually go away.
- Bronchogenic Carcinoma: Most feared cause of cough. It is far more common in smokers but has occurred in non-smokers as well. Fortunately it is an uncommon cause of chronic cough. Most patients suspect lung cancer on abnormal chest x-rays but occasionally need CT scan and bronchoscopy to diagnose and confirm the diagnosis.
- Habit cough and psychogenic cough are important but fortunately less common cause. They are not easy to diagnose. Patients usually don’t accept the diagnosis.
- Chronic interstitial lung disease including pulmonary fibrosis are important lung conditions which can present with cough, and shortness of breath. Even when patient has confirmed diagnosis of pulmonary fibrosis, it is worthwhile to rule out GERD and/or upper airway syndrome as contributing factors to the causeof cough.