International Consensus Diagnostic Criteria for Autoimmune Pancreatitis (AIP)

Autoimmune pancreatitis is a distinct form of pancreatitis characterized clinically by frequent presentation with obstructive jaundice with or without a pancreatic mass, histologically by a lymphoplasmacytic infiltrate and fibrosis and therapeutically by a dramatic response to steroids.

The terms lymphoplasmacytic sclerosing pancreatitis (LPSP) (AIP without granulocyte epithelial lesions (GELs)), and idiopathic duct-centric pancreatitis (IDCP) (AIP with GELs) refer to pancreatic histological patterns in AIP. Because pancreatic histology often is not available, the terms type 1 and type 2 AIP have been introduced to describe the clinical profiles associated with LPSP and IDCP, respectively.

Diagnosis of Definitive and Probable Type 1 AIP Using International Consensus Diagnostic Criteria (ICDC)

Diagnosis	Primary Basis for Diagnosis	Imaging Evidence	Collateral Evidence
Definitive type 1 AIP	Histology	Typical/indeterminate	Histologically confirmed LPSP (level 1 H)
	Imaging	Typical/indeterminate	Any non-D level 1/level 2 Two or more from level 1 (+level 2 D*)
	Response to steroid	Indeterminate	Level 1 S/OOI + Rt or level 1 D + level 2 S/OOI/H + Rt
Probable type 1 AIP		Indeterminate	Level 2 S/OOI/H + Rt

*Level 2 D is counted as level 1 in this setting.

Level 1 and Level 2 Criteria for Type 1 AIP

Criterion	Level 1	Level 2
[P] Parenchymal imaging	Typical: Diffuse enlargement with delayed enhancement (sometimes associated with rim-like enhancement)	Indeterminate (including atypical†): Segmental/focal enlargement with delayed enhancement
[D] Ductal imaging (ERP)	Long (>1/3 length of the main pancreatic duct) or multiple strictures without marked upstream dilatation	Segmental/focal narrowing without marked upstream dilatation (duct size, <5 mm)
[S] Serology [OOI] Other organ involvement	IgG4, >2x upper limit of normal value a or b a. Histology of extrapancreatic organs Any three of the following: (1) Marked lymphoplasmacytic infiltration with fibrosis and without granulocytic infiltration (2) Storiform fibrosis (3) Obliterative phlebitis (4) Abundant (>10 cells/high-power field) IgG4-positive cells b. Typical radiological evidence At least one of the following: (1) Segmental/multiple proximal (hilar/intrahepatic) or proximal and distal bile duct stricture (2) Retroperitoneal fibrosis	IgG4, 1-2x upper limit of normal value a or b a. Histology of extrapancreatic organs including endoscopic biopsies of bile duct‡: Both of the following: (1) Marked lymphoplasmacytic infiltration without granulocytic infiltration (2) Abundant (>10 cells/high-power field) IgG4-positive cells b. Physical or radiological evidence At least one of the following: (1) Symmetrically enlarged salivary/lachrymal glands (2) Radiological evidence of renal involvement described in association with AIP
[H] Histology of the pancreas	LPSP (core biopsy/resection) At least 3 of the following: (1) Periductal lymphoplasmacytic infiltrate without granulocytic infiltration (2) Obliterative phlebitis (3) Storiform fibrosis (4) Abundant (>10 cells/high-power field) IgG4-positive cells	LPSP (core biopsy) Any 2 of the following: (1) Periductal lymphoplasmacytic infiltrate without granulocytic infiltration (2) Obliterative phlebitis (3) Storiform fibrosis (4) Abundant (>10 cells/high-power field) IgG4-positive cells
Response to steroid (Rt)*	Diagnostic steroid trial Rapid (≤2 wk) radiologically demonstrable resolution or marked improvement in pancreatic/extrapancreatic manifestations

*Diagnostic steroid trial should be conducted carefully by pancreatologists with caveats only after negative workup for cancer including endoscopic ultrasound-guided fine needle aspiration.
†Atypical: Some AIP cases may show low-density mass, pancreatic ductal dilatation, or distal atrophy. Such atypical imaging findings in patients with obstructive jaundice and/or pancreatic mass are highly suggestive of pancreatic cancer. Such patients should be managed as pancreatic cancer unless there is strong collateral evidence for AIP, and a thorough workup for cancer is negative.
‡Endoscopic biopsy of duodenal papilla is a useful adjunctive method because ampulla often is involved pathologically in AIP.

 

Diagnosis of Definitive and Probable Type 2 AIP Using ICDC

Diagnosis	Imaging Evidence	Collateral Evidence
Definitive type 2 AIP	Typical/indeterminate	Histologically confirmed IDCP (level 1 H) or clinical inflammatory bowel disease + level 2 H + Rt
Probable type 2 AIP	Typical/indeterminate	Level 2 H/clinical inflammatory bowel disease + Rt

 

Level 1 and Level 2 Criteria for Type 2 AIP

Criterion	Level 1	Level 2
[P] Parenchymal imaging	Typical: Diffuse enlargement with delayed enhancement (sometimes associated with rim-like enhancement)	Indeterminate (including atypical†): Segmental/focal enlargement with delayed enhancement
[D] Ductal imaging (ERP)	Long (>1/3 length of the main pancreatic duct) or multiple strictures without marked upstream dilatation	Segmental/focal narrowing without marked upstream dilatation (duct size, <5 mm)
[OOI] Other organ involvement		Clinically diagnosed inflammatory bowel disease
[H] Histology of the pancreas (core biopsy/resection)	IDCP: Both of the following: (1) Granulocytic infiltration of duct wall (GEL) with or without granulocytic acinar inflammation (2) Absent or scant (0-10 cells/high-power field) IgG4-positive cells	Both of the following: (1) Granulocytic and lymphoplasmacytic acinar infiltrate (2) Absent or scant (0-10 cells/high-power field) IgG4-positive cells
Response to steroid (Rt)*	Diagnostic steroid trial Rapid (≤2 wk) radiologically demonstrable resolution or marked improvement in manifestations

*Diagnostic steroid trial should be conducted carefully by pancreatologists with caveats only after negative workup for cancer including endoscopic ultrasound-guided fine needle aspiration.
†Atypical: Some AIP cases may show low-density mass, pancreatic ductal dilatation, or distal atrophy. Such atypical imaging findings in patients with obstructive jaundice and/or pancreatic mass are highly suggestive of pancreatic cancer. Such patients should be managed as pancreatic cancer unless there is strong collateral evidence for AIP, and a thorough workup for cancer is negative.

 

References:

1. Okazaki K, Chari ST, Frulloni L, Lerch MM, Kamisawa T, Kawa S, Kim MH, Lévy P, Masamune A, Webster G, Shimosegawa T. International consensus for the treatment of autoimmune pancreatitis. Pancreatology. 2017 Jan-Feb;17(1):1-6. [Medline]
2. Khandelwal A, Inoue D, Takahashi N. Autoimmune pancreatitis: an update. Abdom Radiol (NY). 2020 May;45(5):1359-1370. [Medline]
3. Shimosegawa T, Chari ST, Frulloni L, Kamisawa T, Kawa S, Mino-Kenudson M, Kim MH, Klöppel G, Lerch MM, Löhr M, Notohara K, Okazaki K, Schneider A, Zhang L; International Association of Pancreatology. International consensus diagnostic criteria for autoimmune pancreatitis: guidelines of the International Association of Pancreatology. Pancreas. 2011 Apr;40(3):352-8. [Medline]

 

Created Jan 17, 2021.