Mechanisms of pain in chronic pancreatitis.

Pain is a leading symptom in chronic pancreatitis (CP) and often its management necessitates surgical intervention. Nevertheless the presence of different hypotheses, the pathophysiology of pain is not understood, thus the indications for therapy remain controversial. Increased pressure within the ductal system and/or the parenchyma has been suggested to be one of the causes of pain. This controversial theory has been substantiated by the demonstration of a relationship between intrapancreatic pressure and intensity of pain. On the other hand, recent studies have shown the inflammatory involvement of intrapancreatic nerve fibres in a so called "neuroimmune interaction". In fact, infiltration of inflammatory cells around the nerves together with an increase in the number of nerve fibres in the fibrotic pancreatic tissue have been proposed as a possible cause of pain in chronic pancreatitis. Moreover, immunohistological studies have shown that the amount of neurotransmitters, such as substance P and calcitonin gene related peptide, is increased in afferent pancreatic nerves and a close interrelationship between pain and immune cell infiltration of the nerves has been reported in CP. In addition to these hypothesis, extrapancreatic causes such as common bile duct obstruction and duodenal stenosis are discussed. This article review points to the different pathogenic mechanisms of pancreatic pain in CP.