The crux of the management of acute pancreatitis is supportive therapy (e.g., maintaining blood pressure and alleviating pain) and “resting” the pancreas by total restriction of oral food and fluids. In 40% to 60% of cases of acute necrotizing pancreatitis, the necrotic debris becomes infected, usually by gram-negative organisms from the alimentary tract, further complicating the clinical course. Although most individuals with acute pancreatitis eventually recover, some 5% die from shock during the first week of illness; acute respiratory distress syndrome and acute renal failure are ominous complications. In surviving patients, sequelae include sterile or infected pancreatic “abscesses” or pancreatic pseudocysts.
A common sequela of acute pancreatitis (and in particular, alcoholic pancreatitis) is a pancreatic pseudocyst. Liquefied areas of necrotic pancreatic tissue become walled off by fibrous tissue to form a cystic space, lacking an epithelial lining (hence the designation pseudo). The cyst contents are rich in pancreatic enzymes, and a laboratory assessment of the cyst aspirate can be diagnostic. Pseudocysts account for approximately 75% of all pancreatic cysts. While many pseudocysts spontaneously resolve, they can become secondarily infected, and larger pseudocysts can compress or even perforate into adjacent structures.
Fig.17.3A ).Theycanrangeindiameterfrom2cmto30cm.Sincepseudocystsformbywallingoffareasofhemorrhagicfatnecrosis,theytypicallyarecomposedofnecroticdebrisencasedbywallsofgranulationtissueandfibroblastslackinganepitheliallining(see
Fig.17.3B ).Iftheygetinfected,apancreaticabscessisformed.
Chronic pancreatitis is characterized by long-standing inflammation that leads to irreversible destruction of the exocrine pancreas, followed eventually by loss of the islets of Langerhans. Of note, recurrent bouts of acute pancreatitis regardless of etiology can evolve over time into chronic pancreatitis. The prevalence of chronic pancreatitis is difficult to determine but probably ranges between 0.04% and 5% of the U.S. population.
By far the most common cause of chronic pancreatitis is long-term alcohol abuse. Middle-aged men constitute the bulk of patients in this etiologic group. Less common causes of chronic pancreatitis include the following:
Duct Obstruction. Long-standing obstruction of pancreatic duct e.g., by pseudocysts, calculi, neoplasms, or pancreas divisum.
Tropical pancreatitis, a poorly characterized heterogeneous disorder seen in Africa and Asia, with a subset of cases having a hereditary basis.
Hereditary pancreatitis due to mutations in the pancreatic trypsinogen gene (PRRS1), or the SPINK1 gene encoding a trypsin inhibitor (see
Table 17.1
Chronic pancreatitis associated with CFTR mutations. The pathophysiology of chronic pancreatitis in cystic fibrosis is discussed in detail in Chapter 7.
Autoimmune pancreatitis is a pathogenically distinct form of chronic pancreatitis that is associated with the http://ebooksmedicine.net
Fig. 17.3 Pancreaticpseudocyst.(A)Cross-sectionrevealingapoorlydefinedcystwithanecroticbrownishwall.(B)Histologically,thecystlacksanepithelialliningandinsteadislinedbyfibrinandgranulationtissue,withtypicalchangesofchronicinflammation.
presence of IgG4-secreting plasma cells in the pancreas. Autoimmune pancreatitis is one manifestation of IgGrelated disease (Chapter 5), which may involve multiple tissues. It is important to recognize because it responds to steroid therapy.