Cystic fibrosis – effects on the lungs and gut
Lungs
In normal lungs mucus is produced and coats the airways. The cells lining the airways have small hair like projections from their surfaces that beat together to move the mucus up from the bottom of the lungs to the mouth. This mucus carries any dust, particles or bacteria that have been breathed in to the throat where they can be coughed out or swallowed. This is called the mucociliary escalator and is one of the major ways the lungs keep themselves clean and free from infective agents. The normal nose also functions like this.
In cystic fibrosis the mucus is too thick for the mucociliary escalator to function and the mucus blocks off some of the small airways, this is called mucus plugging. This means that instead of moving bacteria out of the lungs the mucus acts as a reservoir within the lungs where bacteria can multiply and cause infection and inflammation. In cystic fibrosis the lungs are normal at birth but repeated cycles of infection and inflammation damage them leading to damage and dilatation of the airways. This is called bronchiectasis. Mucus collects in these abnormal wide areas and further infections result. Mucus in the lungs may become colonised with unusual bacteria that do not cause infections in normal lungs but can in lungs damaged in cystic fibrosis. The nasal passages are also affected and repeated infections and nasal polyps may occur. Much of the extra care and attention in cystic fibrosis is devoted to managing the abnormal mucus thereby preventing and treating infections. The following terms may be used to describe the effects of cystic fibrosis on the lungs in the medical evidence:
- Bronchiectasis – some of the airways are abnormally dilated (wide), mucus can pool in these areas and act as a reservoir for infection.
- Bronchitis – inflammation or infection of the large airways – the bronchi.
- Bronchiolitis – inflammation or infection of small airways – the bronchioles.
- Pneumonia – acute infection of the lungs
- Atelectasis – the alveoli or ‘air sacs’ are collapsed or filled with fluid
- Haemoptysis – coughing up blood
- Pneumothorax – collapsed lung
- Cor pulmonale – heart failure due to severe lung disease
- Respiratory failure – lungs unable to meet the oxygen demands of the body
- Mucoid impaction of bronchi – plugging of large airways by mucus
- Allergic bronchopulmonary aspergillosis – allergic response to fungal infection of the lungs with toxin producing highly allergenic fungi
Gut
The main effect on the gut is again caused by abnormally thick sticky mucus production but this time affecting the pancreas. The pancreas is an exocrine gland that produces digestive enzymes that breakdown food into absorbable nutrients. These enzymes are vital. In cystic fibrosis thick mucus blocks off pancreatic ducts preventing secretion of enzymes. Blockage of ducts causes inflammation in the pancreas which leads to loss of productive capacity. This lack of digestive enzymes is called pancreatic insufficiency. Without enzymes malabsorption particularly of fats and fat soluble vitamins occurs. This leads to malnutrition even though the diet is adequate. Poor growth and poor weight gain is seen and vitamin deficiencies develop. Vitamins A, D, E and K vital for healthy bones, blood clotting and immune defences are affected. In a small number of children with cystic fibrosis the pancreas is not affected.
The pancreas is an endocrine as well as an exocrine gland. Its endocrine function is to produce the hormone insulin that controls blood sugar. Lack of insulin is the cause of diabetes which develops commonly in people with cystic fibrosis.
Summary of main effects
In summary children with cystic fibrosis have normal lung function at birth. This deteriorates over time because of the effects of abnormal mucus production and the tissue damage caused by repeated infections and chronic inflammatory processes particularly in the lungs, and sometimes other organs. Most children have pancreatic insufficiency from birth and the remainder can develop it with time. The treatment of Cystic Fibrosis is mainly directed towards correction of organ dysfunction and relieving symptoms that result from the disease.
Children with cystic fibrosis vary in terms of the severity of their condition e.g. a few children do not develop pancreatic insufficiency and some children maintain good lung function through childhood. Others are severely affected developing respiratory failure and requiring lung transplant before their 16th birthday. Screening of all newborns has recently been introduced throughout the UK with the aim of diagnosing children before lung damage occurs and preserving lung function for as long as possible in affected children.
Cystic fibrosis causes many other problems in the body including liver disease and cystic fibrosis related diabetes. These may add to care needs related to lung and gut complications of cystic fibrosis. As a life threatening condition diagnosed in early childhood with a life expectancy of 38 years at birth the condition, even if well controlled, is likely to have significant effects on the child and their family.
