🩺 Cough

Cough is one of the most common reasons for seeking primary care advice and is a protective reflex intended to clear the airways. It is categorised by duration, which significantly dictates the differential diagnosis: acute cough is usually viral, whereas chronic cough often involves inflammatory, mechanical, or neoplastic triggers. In the UK, guidelines emphasise the 'negative' predictive value of a normal chest X-ray in chronic cases, but alert clinicians to the possibility of malignancy in high-risk populations regardless of initial imaging. Management involves treating the underlying cause rather than mere symptomatic suppression.

Inquiry should establish the duration (acute <3 weeks, subacute 3-8 weeks, chronic >8 weeks), nature (productive vs dry), and associated triggers. Nocturnal cough frequently suggests asthma or heart failure, while cough following meals may indicate GORD or aspiration. A detailed medication history is mandatory to identify ACE inhibitor use. Smoking history, occupational exposures (e.g., asbestos, silica), and systemic 'red flag' symptoms like weight loss, drenching night sweats, or haemoptysis must be explored to exclude life-threatening pathology.

Examination begins with an assessment of respiratory distress and oxygen saturations. The oropharynx should be inspected for signs of post-nasal drip (cobblestoning) or enlarged tonsils. Chest percussion may reveal dullness (consolidation or pleural effusion) or hyper-resonance (emphysema). Auscultation focuses on focal crackles (pneumonia or bronchiectasis), wheeze (asthma or COPD), or fine end-inspiratory 'Velcro' crackles (interstitial lung disease). General signs such as finger clubbing, lymphadenopathy, or cachexia are critical for identifying underlying malignancy or chronic suppuration.

Lower Respiratory Tract Infection (LRTI), Asthma, COPD/Exacerbation, Gastro-oesophageal Reflux Disease (GORD), ACE inhibitor-induced cough, Post-nasal drip, Lung Cancer, Bronchiectasis, Heart Failure (pulmonary oedema), Tuberculosis.

Haemoptysis, significant weight loss, persistent fever, night sweats, new-onset breathlessness, hoarseness lasting >3 weeks, dysphagia, or persistent cough in a smoker/ex-smoker aged >40.

The primary diagnostic tool for any chronic cough or red-flag acute cough is a Chest X-ray. Bedside tests include peak flow monitoring or spirometry to investigate obstructive airway diseases. Sputum microscopy, culture, and sensitivity (MC&S) are indicated if infection or TB is suspected. Full blood count may show eosinophilia in asthma or raised inflammatory markers in infection. If malignancy or interstitial disease is suspected despite a normal X-ray, HRCT chest or CT chest with contrast is the gold standard, often followed by bronchoscopy.

Chronic cough with a normal chest X-ray in a non-smoker is most commonly due to upper airway cough syndrome (post-nasal drip), asthma, or GORD. If ACE inhibitors are the cause, the cough typically resolves within 1-4 weeks of cessation, though it can take up to 3 months. Pertussis (whooping cough) should be considered even in immunised adults if there is a distinctive paroxysmal cough or post-tussive vomiting. Chronic cough associated with weight loss or significant smoking history must be treated as lung cancer until proven otherwise.

Aligned with the MLA content map 'Cough'. Focus on differentiating between benign self-limiting infections and chronic pathology. Note the significance of 'red flags' and the systematic approach to investigation (CXR first). Understanding the mechanism of ACE inhibitors affecting bradykinin breakdown is a common basic science link.