04 April 2017
Most coughs are a result of an infection such as a cold or simple chest infection and usually pass within a week or so. When a cough goes on for 3 weeks or more it should prompt a review. Symptoms such as coughing up blood, chest pain or breathlessness should lead to a more urgent review with your doctor.
In many cases following a consultation with a doctor or a specialist, some straightforward screening tests such as a chest x-ray and blood tests will be arranged as the first steps. This often can rules out many serious problems. However more sophisticated tests such as a CT scan of the chest may be ordered if these original tests point to something more serious (such as a tumour) or if a patient has unresolved symptoms. Apart from identifying cancers, a CT scan can visualise a number of benign conditions such as lung fibrosis (scarring) or bronchiectasis (the small airways are dilated and retain mucous, causing recurrent infections). Both of these conditions will require some ongoing monitoring and possibly treatment so identifying them is important.
Coughs can also be caused by certain medicines such as particular blood pressure tablets called 'ACE Inhibitors' so be sure to point this out if you have recently started taking them - and indeed a full list of a patients current medications is helpful.
In patients with a normal CT scan, the top three causes of cough are:
- post-nasal drip
- gastrooesphageal reflux (GORD).
GORD occurs when small amounts of stomach contents are refluxed back up the gullet and are micro-aspirated into the lungs. This causes a reflex coughing reaction and can also lead to local airway inflammation. GORD is also a known risk factor for bronchiectasis.
Each of these three conditions can be investigated and treatment provided, often with good effect.
Occasionally, a cough that doesn't respond to treatment is due to adult whooping cough – it's self-limiting (ultimately resolving itself without treatment) but can take several weeks to go. A simple blood test can see if you have had whooping cough.
In some patients no identifiable cause is found despite extensive tests. In these cases, medicines can be prescribed to dampen the cough reflex down but may not completely eliminate it.
With all persistent coughs, a serious cause should be ruled out - but remember that in many people no sinister cause is found and the cough will often get better on its own.
Dr Tim Ho is a Consultant Chest Physician specialises in conditions of the lungs including persistent cough, breathlessness, recurrent chest infections, the investigation of lung cancer and obstructive sleep apnoea.