What happens in primary biliary cholangitis?
In PBC, inflammation develops around the small bile ducts within the liver, which gradually become blocked due to this inflammation. This process gets worse very slowly, and the number of damaged and blocked bile ducts gradually increases.
As bile cannot flow down bile ducts, it builds up in the liver cells which eventually become inflamed and then damaged by the accumulation of bile. The substances in bile may also spill over into the bloodstream, causing itching and yellowing of the whites of your eyes and your skin (jaundice).
In the early stages of the disease, the main problems caused by PBC are due to the build-up of substances in the liver and bloodstream which would normally be drained into the first part of the gut (small intestine), known as the duodenum, as part of bile.
As damage to the liver cells gets worse, scarring (cirrhosis) may begin in the liver. The scarred liver cannot function properly and over time liver failure may develop. Cirrhosis occurs only in the later stages of the disease. The rate of decline from early stages of the disease to the later, more serious, stages of the disease can vary from person to person.
Not all people with PBC develop cirrhosis. If cirrhosis does occur, it typically develops several years after the disease first begins.
What are bile and bile ducts?
Bile is a yellow-green liquid that contains various chemicals and bile salts. Bile helps you to digest food, particularly fatty foods. It also helps the body to absorb certain vitamins (A, D, E and K) from the food that you eat.
Bile is made by liver cells. Liver cells pass out bile into a network of tubes called bile ducts. These join together to form the larger common bile duct. Bile is constantly formed and drips down the tiny bile ducts, into the common bile duct. It is then stored in the gallbladder, which squeezes it out into the duodenum when you eat food containing fats.
The gallbladder is a pouch off the common bile duct; it lies under the bottom, front edge of the liver. It is a reservoir that stores bile but it also concentrates it. The gallbladder squeezes (contracts) when we eat, as the bile is needed to aid digestion. This empties the stored bile back into the common bile duct and out into the duodenum.
What does the liver do?
The liver is in the upper right part of the tummy (abdomen). Its functions include:
- Storing glycogen (fuel for the body) which is a starch made from sugars. It acts as 'quick access' energy for the body. When required, glycogen can be quickly broken down into glucose which is released into the bloodstream.
- Helping to process fats and proteins from digested food.
- Making proteins that are essential for blood to clot (clotting factors).
- Processing many medicines which you may take.
- Helping to remove or process alcohol, poisons and toxins from the body.
- Making bile which passes from the liver to the gut and helps to digest fats.
How does primary biliary cholangitis occur?
The immune system normally defends us by attacking bacteria, viruses, and other germs with antibodies, white blood cells, and other defence mechanisms.
In people with autoimmune diseases, the immune system turns against and attacks tissues of the body. It is not clear why this happens:
- Some people seem to have a tendency to develop autoimmune diseases. Their immune systems are more readily triggered into attacking parts of their own body. In such people, something may trigger the immune system to attack the body's own tissues. The exact trigger is not known. Possible triggers that have been suggested are some kind of infection or some kind of poison (toxin).
- There may also be a genetic tendency to develop PBC, as it seems to run in some families.
In people with PBC, the immune system attacks the cells that line the small bile ducts in the liver. This causes inflammation and damage in and around these bile ducts. Gradually they become scarred and may block off.
People with PBC have an increased chance of developing other autoimmune diseases. For example, Sjögren's syndrome, two thyroid diseases called Graves' disease and Hashimoto's thyroiditis, Raynaud's phenomenon and scleroderma.
Did you find this information useful?
- EASL Clinical Practice Guidelines: The diagnosis and management of patients with primary biliary cholangitis; European Association for the Study of the Liver (2017)
- Management of cholestatic liver diseases; European Association for the Study of the Liver (June 2009)
- British Liver Trust
- I J Beckingham and S D Ryder; ABC of diseases of liver, pancreas, and biliary system: Investigation of liver and biliary disease. BMJ 2001 322:33-36.