Pancreatitis is the medical term for inflammation of the pancreas. It is one of the more common pancreas problems often associated with gallstones and alcohol misuse. The pancreas is an elongated gland lies in the upper abdomen and influences digestion, absorption, metabolism and storage of nutrients. It has both endocrine and exocrine functions which are discussed in detail under pancreas function.
Most of the pancreatic tissue is dedicated to its exocrine functions, which include the production and secretion of the pancreatic enzymes. These digestive enzymes are released in an inactive form and only activated once in the lumen of the duodenum where it acts on food.
Pancreatitis occurs when the outflow or dormant state of these digestive enzymes are hampered by any one of the causative factors. Activation of the enzymes while in the gland causes injury as the enzymes begin to digest pancreatic tissue. Therefore pancreatitis initially affects the exocrine parenchyma (pancreatic tissue) but as it progresses, it affects the endocrine parenchyma as well.
In acute pancreatitis the damage to the pancreatic tissue is usually reversible. Severe cases also affects surrounding tissues because the pancreas has a poorly developed capsule and therefore the activated pancreatic enzymes may cause inflammation of the duodenum, bile duct and sometimes even the transverse colon and splenic vein.
Acute interstitial pancreatitis is the milder form of pancreatitis and is marked by mild inflammation of the pancreatic parenchyma and fat necrosis.
Severe forms like acute necrotizing pancreatitis results in death of the parenchymal tissue (necrosis), particularly the acini and ductules, due to proteolytic digestion. There may also be mild hemorrhage into the pancreatic tissue due to injury of the blood vessels supplying the gland.
In the most severe form of acute pancreatitis known as hemorrhagic pancreatitis, there is widespread damage of the pancreatic tissue and extensive hemorrhaging into the gland.
In chronic pancreatitis, the damage to the pancreatic tissue is extensive usually affecting both the exocrine and endocrine parenchyma. Fibrosis of the pancreatic tissue is present due to the prolonged inflammation. The damage associated with chronic pancreatitis is usually irreversible.
Usually chronic pancreatitis is a consequence of repeated bouts of acute pancreatitis, although it may arise without a history of acute pancreatitis. Typical histological findings include extensive fibrotic scarring of the parenchyma, especially the exocrine parenchyma, with enlargement of the pancreatic duct and a atrophy of the acini. The islets of Langerhans which are responsible for the exocrine functions of the pancreas may be affected to varying degrees but in chronic pancreatitis, it is usually not unaffected. Hardening of the gland with focal areas of calcification may also be evident in chronic pancreatitis.
Hereditary pancreatitis is a type of recurrent pancreatic inflammation caused by genetic factors. In this case, mutations of the PRSS1 or SPINK1 genes affects the mechanisms that inhibit trypsinogen activation within the pancreas. Most cases of hereditary pancreatitis are characterized by repeated attacks of acute pancreatitis but a significant number of cases will progress to chronic pancreatitis.
Autoimmune pancreatitis (lymphoplasmacytic sclerosing pancreatitis) is a result of a high concentrations of immune cells (IgG4-producing plasma cells) within the pancreatic parenchyma. These cells are responsible for ongoing inflammation in the pancreas.