Level 1 findings:
(1) "typical" parenchymal imaging (diffuse enlargement with delayed enhancement)
(2) ductal imaging on ERCP (long or multiple strictures without upstream dilatation)
(3) histology showing idiopathic duct-centric pancreatitis (IDCP) with both of the following:
(3a) granulocytic infiltration of duct wall with/without acinar inflammation
(3b) IgG4 positive cells 2-10 per high per field (HPF)
(4) rapid response to corticosteroids (Rt) affecting pancreatic and extrapancreatic manifestations
where:
• Long stricture is greater than one third of the total duct length.
• Rapid response to corticosteroids is less than 2 weeks.
Level 2 findings:
(1) "indeterminate" parenchymal imaging (focal enlargement with delayed enhancement)
(2) ductal imaging on ERCP (focal narrowing without marked upstream dilatation, < 5 mm)
(3) clinically diagnosed inflammatory bowel disease:
(4) histology showing both of the following:
(4a) granulocytic and lymphoplasmacytic acinar infiltrate
(4b) IgG4 positive cells 2-10 per high per field (HPF)
Definitive - both of the following:
(1) parenchymal imaging typical or indeterminate (level 1 or 2)
(2) one of the following:
(2a) histology level 1 (IDCP)
(2b) histology level 2 + inflammatory bowel disease + response to corticosteroids
Probable - both of the following:
(1) parenchymal imaging typical or indeterminate (level 1 or 2)
(2) (level 2 histology or inflammatory bowel disease) + response to corticosteroids
