The cornerstone of diagnosis of CP is evidence of structural damage of pancreas esp if with impaired pancreatic function. First line of diagnostic investigation is CT mutliphase, MRCP or EUS. EUS with standard criteria has become more applicable nowadays, however it could be operator dependant.
In complement to the answer above, you can use the following link (https://pancreasfoundation.org/patient-information/chronic-pancreatitis/chronic-pancreatitis-testing-and-diagnosis/) to get more informations about chronic pancreatitis diagnosis.
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All tne image methods can find estructural damage of the pancreas however the cornestone of the diagnosis is the evaluation of pancretic exocrine function that may diagnnose chronic pancreatitis even before estructural damage be found by image methods