Pancreatitis is the inflammation of the tissue within the pancreas. It develops when the digestive enzymes that are made in the pancreas start to attack the cells of the pancreas and nearby tissue.

There are two forms of pancreatitis, acute and chronic. Most episodes of acute pancreatitis resolve within a few days of hospital treatment. The chronic form, which is thought to be due to recurrent long-term damage to the pancreas, can last for months and can cause irreversible damage and scarring.

The role of the pancreas in digestion

The pancreas makes several digestive enzymes, including trypsin, which breaks down proteins and pancreatic amylase, which breaks down carbohydrates. Normally, when these enzymes are released by the pancreatic cells that make them, the enzymes are in an inactive from.

They remain inactive within small fluid-filled sacs called zymogen granules. This keeps the enzymes away from the tissues of the pancreas and the enzymes are only activated when they pass through the pancreatic duct and into the small intestine.

What happens in pancreatitis?

When someone develops pancreatitis, this is a sign that something has happened to disrupt this system. Digestive enzymes become active within the pancreas and start to digest it, which causes pancreatic inflammation. Once the cells become damaged, more active enzymes are released, leading to a vicious cycle of damage and inflammation.

  • Acute pancreatitis is a limited episode of pancreatic inflammation that gets better after a few days with treatment.
  • In chronic pancreatitis, the inflammation persists beyond a few days, and the pancreatic tissues are slowly but progressively scarred and destroyed. Repeated episodes of acute pancreatitis can make the chronic form more likely.

Causes of acute pancreatitis

Acute pancreatitis results from the release of active digestive enzymes within the pancreas and this can happen if:

  • Gallstones block the bile duct: this can also block the pancreatic duct and traps enzymes, causing trypsin to become active inside the pancreas.
  • You binge drink: alcohol abuse seems to activate trypsin in the pancreas. Acute pancreatitis affects about one in 10 people who regularly drink more than 10 units of alcohol a day. An attack usually occurs 6-12 hours after excessive drinking.
  • You have pancreatic cancer: the tumour can block the pancreatic duct and lead to the build-up of digestive enzymes inside the pancreas.

There are also rarer causes and risk factors and in about 15 % of cases of acute pancreatitis, no cause can be found.
One rare but well-established link is between endoscopic retrograde cholangiopancreatography (ERCP) and acute pancreatitis. ERCP is a specialised form of endoscopy that can be used to investigate the bile duct and pancreatic duct for signs of narrowing, blockages and other complications. Around 5 % of people who have ERCP develop acute pancreatitis subsequently.

Causes of chronic pancreatitis

In more than 70 % of cases, the underlying cause is alcohol abuse that is long-standing. Someone can drink heavily for several years without symptoms but then acute pancreatitis develops, becomes frequent, and then does not clear up.

People with alcoholic chronic pancreatitis have usually drunk more than 10 units of alcohol per day for 10-15 years.
In over 20 % of cases, no cause can be identified. Malnutrition, high levels of calcium or fats in the blood, rare genetic conditions including cystic fibrosis, some autoimmune diseases and some congenital structural problems in the pancreas have been associated with chronic pancreatitis.

Symptoms and complications of pancreatitis

The main symptom of both forms is severe pain just below the ribs that spreads to the back. It often starts suddenly and gets worse. The person affected then often develops a fever and develops nausea, diarrhoea and vomiting. People usually feel very ill and need hospital treatment.

If attacks of pancreatitis happen regularly, this can lead to weight loss and malnutrition.
Chronic pancreatitis can cause the symptoms above, plus abdominal swelling. As the pancreas becomes more damaged, pseudocysts start to form. These contain debris and fluid and they can rupture, causing bleeding. The pancreatic duct and the bile duct can also become narrowed or blocked by scar tissue.

When damage becomes widespread, the pancreas can no longer produce insulin or digestive enzymes. This can cause type 2 diabetes (because of the lack of insulin) and digestive problems including oily and smelly stools, as fats and some proteins can no longer be digested. People who have chronic pancreatitis are also at a higher risk of developing pancreatic cancer.

What is necrotising pancreatitis?

Necrotising pancreatitis develops in about a fifth of people with the chronic form. The pancreas and neighbouring tissues start to die and release pancreatic juice, including active digestive enzymes, into the body cavity. This is a medical emergency as it leads to:

  • Low blood pressure
  • Dehydration
  • Shock
  • Heart, lung or kidney failure
  • Internal bleeding.