3.1　Introduction

Pancreatitis results from an insult to the pancreas that may lead to trypsin activation，inflammatory cell infiltration，edema，cell death，fibrosis and organ damage（Sarles 1991）.In the majority of children，the inflammation is self-limited and reversible with only one acute pancreatitis（AP）episode over their lifetime（～1:10,000）（Morinville et al.2010；Nydegger et al.2007）.In a subset of patients（～10-34%），AP may progress to acute recurrent pancreatitis（ARP）（Bai et al.2011；Beger et al.1997）and a subset（～0.5-2.7/100,000 cases）may develop chronic pancreatitis（CP）（Pant and Sferra 2015；Spanier et al.2013；Yadav et al.2011）.

The incidence，characteristics，of CP in children are poorly defined and mostly based on retrospective cohorts.A recent pediatric multi-center collaboration，INternational Study Group of Pediatric Pancreatitis:In Search for a CuRE（INSPPIRE）has assumed the task of studying the disease characteristics of ARP and CP in pediatrics（Morinville et al.2012，2014；Schwarzenberg et al.2015；Ting et al.2015）.Diagnostic criteria for pediatric AP，ARP and CP are listed on Table 11.6（Conwell and Banks 2008；Deng et al.2005；Morinville et al.2012；Muddana et al.2010；Whitcomb 2004）.

Recurrent inflammation and subsequent fibrosis may further lead to organ dysfunction with pancreatic exocrine and/or endocrineinsufficiency（Conwell and Banks 2008；Deng et al.2005；Muddana et al.2010；Whitcomb 2004）.Current diagnostic criteria is reflective of the injury sustained by the pancreas and can include changes in duct morphology，gland atrophy，calcifications or pancreatic insufficiency.An evidence-based algorithm to confirm the diagnosis of CP proposed by the American Pancreatic Association utilizes criteria that can be sequentially assessed starting with imaging findings as well as pancreatic functional studies（Conwell et al.2014）.There are no established criteria to diagnose early or minimal change CP.(https://www.daowen.com)

Table 11.6　Definitions of pancreatitis in children（Conwell and Banks 2008；Deng et al.2005；Morinville et al.2012；Muddana et al.2010；Whitcomb 2004）

aSuggestive imaging findings of CP include:
·Ductal changes:irregular contour of the main pancreatic duct or its radicles；intraductal filling defects；calculi，stricture or dilation
·Parenchymal changes:generalized or focal enlargement，irregular contour（accentuated lobular architecture），cavities，calcifications，heterogeneous echotexture