Most cases of acute pancreatitis are closely linked to gallstones or to alcohol consumption, although the exact cause isn't always clear.

Gallstones

Gallstones are hard pieces of stone-like material that form in your gallbladder. They can trigger acute pancreatitis if they move out of the gallbladder and block the opening of the pancreas.

The blockage can disrupt some of the enzymes (chemicals) produced by the pancreas. These enzymes are normally used to help digest food in your intestines, but they can start to digest the pancreas instead if the opening is blocked.

However, not everyone with gallstones will develop acute pancreatitis. Most gallstones don't cause any problems.

Alcohol consumption

It's not fully understood how alcohol causes the pancreas to become inflamed. One theory is that it interferes with the normal workings of the pancreas, causing the enzymes to start digesting it.

Whatever the cause, there is a clear link between alcohol use and acute pancreatitis. A very large study found that people who regularly drank more than 35 units of alcohol a week were four times more likely to develop acute pancreatitis than people who never drank alcohol (35 units is the equivalent of drinking around 16 cans of strong lager or four bottles of wine a week).

Binge drinking, which is drinking a lot of alcohol in a short period of time, is also thought to increase your risk of developing acute pancreatitis.

Other causes

Less common causes of acute pancreatitis include:

• accidental damage or injury to the pancreas – for example, during a procedure to remove gallstones or examine the pancreas
• certain types of medication, such as some antibiotics or chemotherapy medication – acute pancreatitis can be an unexpected side effect of these in a small number of people
• a viral infection – such as mumps or measles
• a complication of cystic fibrosis
• certain rare conditions – including hyperparathyroidism, Reye's syndrome and Kawasaki disease

Severe pancreatitis

Little is known about why some people develop severe acute pancreatitis. Factors thought to increase your risk include:

• being 70 years of age or over
• being obese (a person is considered obese if they have a body mass index (BMI) of 30 or above)
• having two or more alcoholic drinks a day
• smoking

Researchers have also discovered that people with a specific genetic mutation, known as the MCP-1 mutation, are eight times more likely to develop severe acute pancreatitis than the general population. A genetic mutation is where the instructions (DNA) found in all living cells become scrambled, resulting in a genetic disorder or a change in characteristics.