Friday, June 29, 2012

Cough

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Note: Special thanks to BestPractice for the information in this post.

This post has been written by a medical student. This website is a collection of my reflections on life and on medicine. The target audience is technically myself, and perhaps my family. This website includes information on things I am interested in and am learning about. The information here has not been verified and should not be construed as medical advice in any way. If you are sick you should contact a local doctor for advice and management.
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Cough - it's such an simple thing, and yet, it's always so important to get the simple things right. 

The wife of a good friend of mine was recently diagnosed with scleroderma following a long period of dry cough. It had been mistaken for asthma for a long time and I do not know the details about the case but it has made me determined to understand 'cough' as a symptom much better than I currently do.

Differential Diagnoses

Common causes of cough includes upper airway cough syndrome (formerly known as postnasal drip*), asthma*, GORD*, non-asthmatic bronchitis*, chronic bronchitis, use of ACE-I, pneumonia, post-infectious cough and whooping cough.

Post-infectious coughs are the most common cause of coughing but most cases are self-limiting and if a cough has persisted for over 8 weeks then a systematic approach to elucidating cause and treatment is necessary.

Conditions marked out above with an * represent the most common causes of cough in patients who do not smoke and are not on ACE-I. Whooping cough in adults will not necessarily present with the 'whoop whoop' presentation that is seen in young children.

Less common etiologies to consider include conditions that irritate the airways such as bronchiectasis, chronic suppurative lung disease, endobronchial tumors, granulomatous disease and foreign bodies. These conditions should show up on a CXR.

Aside from the airways, irritation of the lung parenchyma can also cause cough and conditions include interstitial lung disease due to hypersensitivity pneumonitis or occupational/environmental exposure.

Other conditions to consider (but these are very rare) include systemic diseases such as RA, sarcoidosis and autoimmune conditions such as SLE and scleroderma.

Psychogenic cough may be diagnosed if a thorough evaluation has ruled out all other causes.

Investigations

Having heard my friend's story, I almost wished there were some way of picking up rare conditions like scleroderma more quickly. The thing is though, given how rare it is, it does not make sense to screen everyone for the condition until other differentials have been exhausted. I keep thinking "could this have been picked up earlier?", "would it have made a difference to her prognosis?" and so far I do not have an answer (being a medical student and not having all the details about the case and scleroderma itself). Nonetheless, here is some paraphrased information from 'BestPractice' (BMJ).

Chronic cough as a sole symptom does not usually represent an urgent medical condition. However, faster, more comprehensive evaluation should be carried out if other symptoms such as dyspnea, naemoptysis, weight loss, fever or chest pain are present, or if the patient is immunocompromised.

Investigations to consider (depending on symptoms and patient factors) include:

Lung Cancer: CXR & tissue diagnosis
Asthma: Spirometry + bronchodilators
Pneumonia: CXR, sputum culture
TB: CXR, sputum culture for AFB
Whooping cough: Microbiology and serologic testing
Interstitial pulmonary fibrosis: CXR, spirometry

As you can see, a CXR would be a great start as it picks out quite a lot of pathology and exposure to radiation is minimal. 

After the CXR, the next step is guided by your clinical assessment and investigation results.

Consider the following options:
- upper airways cough syndrome: sinus CT and ENT referral
- asthma: evaluate adherence to treatment, med review
- GORD: try treating with PPIs, H2-antagonists etc


Cough should resolve completely before diagnosis is confirmed.


If there is still no diagnosis:
1) High res chest CT
2) Bronchoscopy
3) CT sinuses & naso-endoscopy
4) 24 hour esophageal pH


These tests are more invasive and results in greater exposure to radiation so should not be done without due consideration.

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