Any inflammation of the pancreas is called pancreatitis.

Acute pancreatitis results in severe inflammation of the gland and patients may be seriously unwell.

Chronic pancreatitis develops either as the result of repeated attacks of acute pancreatitis or as the result of other injuries to the pancreas (see below).

It is thought that the damage to the pancreas occurs as the result of digestive enzymes leaking into the pancreas and starting to digest it. This sets up inflammation, and when the inflammation settles, the scarring process distorts the pancreas making further attacks of inflammation likely. Thus a vicious cycle develops.

As a result of prolonged damage to the pancreas, the pancreas fails to produce enough digestive enzymes to permit adequate digestion of food. This leads to weight loss and the frequent passage of pale greasy stools which contain excess amounts of fat. Further, the destruction of the cells which produce insulin may lead to the development of diabetes.

The symptoms are very variable.

Pain occurs in most patients at some stage of the disease. This may vary in intensity from mild to severe. It may last for hours or sometimes days at a time and may require strong painkillers to control it. It often radiates through to the back and can sometimes be relieved by crouching forward. It is commonly brought on by food consumption and so patients may be afraid to eat. It is also commonly severe through the night. The pain varies in nature, being gnawing, stabbing, aching or burning, but it tends to be constant and not to come and go in waves. It may sometimes burn itself out but can remain an ongoing problem.

The mechanism of the pain is unclear. It seems to be related to pancreatic activity since it is frequently caused by food, especially fatty or rich foods. Some patients will have obstruction to the small ducts in the pancreas by small stones, and this is thought to cause back pressure and destruction of the pancreas. There is no relationship between the severity of the pain and the severity of the pancreatic inflammation.

The pain is often difficult to diagnose and can be mistaken for pain caused by virtually any other condition arising from the abdomen or lower chest.

It can be difficult to distinguish pain caused by pancreatitis from pain caused by a peptic ulcer, irritable bowel syndrome, angina pectoris, gallstones.

Diabetes is also a common symptom which affects over half of all patients with long-standing chronic pancreatitis. Long-standing chronic inflammation results in scarring of the pancreas which destroys the specialised areas of the pancreas which produce insulin. Deficiency of insulin results in diabetes. Diabetes causes thirst, frequent urination and weight loss. It may be possible in the early stages of chronic pancreatitis to treat the diabetes with tablets, but in the late stage of chronic pancreatitis, insulin injections are usually needed.

Diarrhoea occurs in just under half of patients. Normally, all the fat in food is broken down by enzymes from the pancreas and small intestine, and the fat is then absorbed in the small bowel. With a reduced level of digestive enzymes the fat is not absorbed. When the fat reaches the large intestine, it is partially broken down by the bacteria in the colon. This produces substances which irritate the colon and result in diarrhoea. The undigested fat also traps water in the faeces, resulting in pale, bulky, greasy stools which are difficult to flush away. They may make the water in the toilet look oily, smell offensive and may be associated with bad wind.

Weight loss occurs in virtually all patients with chronic pancreatitis. It is due to failure to absorb calories from food, and diabetes may also contribute to this. In addition, patients may be afraid to eat because eating brings on the pain. Depression is also common in chronic pancreatitis and this can also reduce appetite and lead to weight loss.

Jaundice (when patients develop yellow eyes and skin) occurs in about a third of patients with chronic pancreatitis. It is usually due to damage to the common bile duct which drains bile from the liver to the duodenum. The common bile duct normally passes though the head of the pancreas. In long-standing chronic pancreatitis, the scarring in the head of the pancreas narrows the common bile duct. Some degree of narrowing may occur in up to half the patients with chronic pancreatitis but when the narrowing is severe, it prevents the bile draining from the liver into the duodenum. It then spills back into the blood and the patient's eyes and skin become yellow. In addition, the stools become paler (since bile makes the stools brown) and the urine becomes dark (because it contains more bile than normal).

Vomiting after meals is a less common symptom but can occur as a result of severe pain. It may also be due to duodenal ulceration, which is often connected with chronic pancreatitis. In rare cases, the duodenum may be narrowed as a result of scarring secondary to chronic pancreatitis.

Vitamin and mineral deficiency. Prolonged passage of stools containing fat can result in low levels of calcium and magnesium in the blood. In addition, some vitamins may not be absorbed properly. This includes vitamins D and A.