There are several known causes including:

• underlying genetic disease such as cystic fibrosis (where the mucus in the bronchial tubes is too thick), and primary ciliary dyskinesia (where the cilia lining the bronchial tubes do not beat properly)
  
  
• mechanical obstruction of the bronchial tubes by inhaled foreign bodies (e.g. peanuts)
  
  
• healing of the tubes resulting in puckering and scarring, causing obstruction
  
  
• inhaling stomach acid which has been regurgitated back into the gullet
  
  
• too little immunity to infection (for example after infantile pneumonia from whooping cough or measles, or lack of antibodies which occasionally occurs after a virus infection in adult life)

However, over half the patients with bronchiectasis in the UK have no obvious cause for it.

The most common symptom is coughing up nasty phlegm, often in large quantities, every day, which is socially embarrassing and very tiring. Even taking this into account, there is often excessive tiredness with lack of concentration. These symptoms frequently result in the patient being accused of smoking. In fact, 80 per cent of patients have never smoked and most of the remainder have stopped. Eighty per cent of patients also have wheezy shortness of breath and a runny nose, and one third suffer from chronic sinusitis.

Less common symptoms are coughing blood (haemoptysis), chest pain, and joint pain. Very rarely, there may be additional symptoms of associated conditions, for example bloody diarrhoea from ulcerative colitis, rheumatoid arthritis, and infertility (mainly in men).

When a doctor sees a patient with a persistent cough, producing infected sputum, there are three categories of tests which should be carried out:

• a test to determine whether the symptoms are due to bronchiectasis and, if so, its distribution and severity; this is done by high-resolution computerised tomography (CT) scanning, which is painless
  
  
• tests to see if it has affected lung function, to determine what bacteria are present by sputum culture, and to determine whether the inflammation is active by white cell scanning
  
  
• tests to detect known causes of bronchiectasis (blood tests, and a simple test of mucus clearance in the nose, measuring the speed of beating of the cilia and how much salt is present in sweat); a fibre-optic bronchoscopy may be necessary to exclude a mechanical obstruction; in men, tests of the number of sperm and their motility may be required

There are seven major components of treatment. The efficiency of treatment is monitored, to detect early progression of disease and to enable treatment to be rapidly modified:

• if there is no underlying cause which might cause bronchiectasis to recur, and the bronchiectasis is localised to a single area of the lung which could be removed without impairing breathing, then removal by operation is a cure
  
  
• the cause, if determined, must be treated (for example, antibody replacement for deficiency)
  
  
• utilising gravity to drain the infected tubes
  
  
• improvement of airflow through the bronchial tubes by anti-asthma treatment
  
  
• treatment of nose or sinus infection, and runny nose, using nasal drops and sprays
  
  
• antibiotics to treat infections, administered at regular intervals or continuously, by intravenous or inhaled routes
  
  
• treatment of any associated disease

In addition, a number of treatments to assist in mucus clearance and to reduce inflammation are being tested for the future. Prevention will rely on future identification of people who are susceptible to the disease.