5.5　Limitations of Diagnostic ERCP

Besides other diseases，potential confounding factors for diagnosis include underfilling of the pancreatic duct with contrast medium（Forsmark and Toskes 1995；Forsmark 2000），normal aging effects（Nagai and Ohtsubo 1984；Ross and Forsmark 2001；Ikeda et al.1994），a recent attack of AP and post-stenting effects（Nagar and Gorelick 2005；Conwell et al.2014），which can produce changes within the pancreatic duct that mimic those seen in CP.Theseconditions limit the clinicians’ability to interpret the pancreatogram accurately and may induce false positive results.

Moreover，false negative results could be led by ERCP or other imaging methods because CP can exist not only in the absence of any changes within the pancreatic duct but also with minimal or subtle ductal abnormalities，which are defined as small-duct disease by Forsmark et al.（Forsmark and Toskes 1995；Feldman et al.2015；Forsmark 2000）.Compared with the big-duct disease with substantial abnormalities of the pancreatic structure and function capable of being detected by a wide variety of diagnostic tests，the small-duct disease is much more difficult to be identified，as both imaging studies and functional tests could be normal.Thus，only tests of maximum sensitivity have a chance of making the diagnosis（Nagar and Gorelick 2005）.(https://www.daowen.com)

Another limitation of the diagnostic ERCP is that the extent of morphologic changes does not correlate highly with the clinical presentation and the degree of the organ impairment or its functional status（Forsmark 2013；Sarner and Cotton 1984；Ramesh 2002；Whitcomb et al.2016）.Early histological damage may not involve the pancreatic duct and subtle exocrine or endocrine insufficiency could precede pathognomonic abnormalities of the pancreatic structure visible on routinely performed imaging studies.On the other hand，a group of patients with detectable changes in the MPD have not developed any symptoms during the course of the disease.Therefore，morphological as well as clinical and functional parameters are recommended to be used in a complementary manner to make a comprehensive assessment（Schreyer et al.2014）.