Endoscopic evaluation of factors contributing to intrapancreatic biliary stricture in autoimmune pancreatitis.

BACKGROUND

Intrapancreatic bile duct stricture in autoimmune pancreatitis (AIP) is usually diagnosed as sclerosing cholangitis even if the stricture is limited to the intrapancreatic area. However, it is not known whether compression caused by pancreatic edema or biliary wall thickening causes such a biliary stricture.

OBJECTIVE

Our purpose was to clarify the factor that contributes to intrapancreatic biliary stricture in AIP: pancreatic head lesion or biliary wall thickening.

DESIGN

Single-center retrospective study.

SETTING

This study was performed in a tertiary care academic medical center.

PATIENTS

Fifty-six patients with AIP were included.

MAIN OUTCOME MEASUREMENTS

The relationship between the presence of a pancreatic head lesion and intrapancreatic biliary stricture was examined. In addition, the relationship between the extent of the intrapancreatic biliary stricture and the wall thickening was evaluated.

RESULTS

Among 44 patients with a pancreatic head lesion, 41 (93%) had intrapancreatic bile duct stricture. Among 12 patients without a pancreatic head lesion, only 2 had such a stricture (P < .0001). Intraductal US showed average intrapancreatic biliary wall thickening with severe stricture of 2.7 +/- 1.0 mm, significantly thicker than that with mild stricture (1.9 +/- 0.35 mm; P = .0200).

LIMITATIONS

Intraductal US was not performed in all patients.

CONCLUSIONS

Both pancreatic edema and biliary wall thickening influenced intrapancreatic biliary stricture in AIP. This type of stricture should be differentiated from extrapancreatic biliary stricture that may be caused by biliary wall thickening only.