Imaging of Pancreatitis

Abstract

Acute pancreatitis is an acute inflammatory process of the pancreatic gland that can involve pancreatic parenchyma or distant organs. The incorporation of the revised Atlanta classification system into everyday practice would provide the use of a standardized terminology and the chance to correctly classify and recognize every imaging finding of acute pancreatitis. It refers to diagnostic criteria, clinical classification—both phases (early and late) and severity (mild, moderately severe, and severe) of acute pancreatitis—morphological classification (interstitial edematous pancreatitis and necrotizing pancreatitis), and complications (organ failure, systemic and local complications). In the revised Atlanta classification, the most important local complications are the pancreatic and peripancreatic collection, and they may be sterile or infected; we should distinguish various types of collections: acute peripancreatic fluid collection (APFC), pseudocyst, acute necrotic collection (ANC), and walled-off necrosis (WON). The parameters for this classification are the time course ( 4 weeks) and the presence of necrosis. Chronic pancreatitis (CP) is an inflammatory disease characterized by progressive and irreversible distortion and destruction of the pancreatic parenchyma, with progressive loss of the endocrine and exocrine function of the gland. The clinical diagnosis of chronic pancreatitis is usually achieved only in advanced disease. The etiology and the pathophysiology of chronic pancreatitis are not well defined. The TIGAR-O risk factor system lists factors associated with chronic pancreatitis. Imaging modalities in the evaluation of CP typically include enhanced computed tomography (CT), MRI with magnetic resonance cholangiopancreatography (MRCP), and ultrasound with a transabdominal or endoscopic approach. The morphological classification of chronic pancreatitis divides CP in macro- and micro-obstructive forms. In the early stages of chronic pancreatitis, pancreatic alterations are usually unspecific and inconclusive. In advanced disease, parenchymal and ductal alterations are irreversible and can be limited to the secondary ducts (small-duct form) or might extend to the main pancreatic duct (large-duct form). The consequence of the obstruction of the pancreatic ductal system is the precipitation of dense protein plugs within the ducts, which gradually calcify in small or large calcifications. Other forms of CP include paraduodenal pancreatitis, autoimmune pancreatitis, and hereditary chronic pancreatitis.