A PROPOSAL FOR DIFFERENTIATION BETWEEN EARLY‐ AND ADVANCED‐STAGE AUTOIMMUNE PANCREATITIS BY ENDOSCOPIC ULTRASONOGRAPHY

Abstract

We evaluated the characteristic endoscopic ultrasonography (EUS) findings of early autoimmune pancreatitis (AIP). Nineteen patients with AIP were identified from our database. We reviewed the following features of EUS as being potentially characteristic of early AIP: hyperechoic foci, hyperechoic strands, lobularity, hyperechoic pancreatic duct margins and reduced echogenicity. According to the Cambridge classification for chronic pancreatitis, we classified AIP into early AIP (Grades 0-2) and advanced AIP (Grades 3-5) and examined the histopathological findings in each stage of AIP. There were nine cases of early AIP and 10 cases of advanced AIP. Five of the nine early cases of AIP showed spontaneous remission without corticosteroid therapy (P < 0.05). The EUS findings were as follows (early vs advanced): hyperechoic foci, 100% (9/9) vs 100% (10/10); hyperechoic strands, 66.7% (6/9) vs 70% (7/10); lobularity, 77.8% (7/9) vs 20% (2/10); hyperechoic pancreatic duct margin, 88.9% (8/9) vs 30% (3/10); reduced echogenicity, 88.9% (8/9) vs 90% (9/10). Lobularity and hyperechoic pancreatic duct margin were detected at a significantly higher frequency in early AIP than in the advanced AIP patients (P < 0.05). Regarding the histopathological findings, acinar cells were better preserved in the cases of early AIP, whereas acinar cells were reduced in number and replaced by massive fibrosis in the patients with advanced AIP. Lobularity and hyperechoic pancreatic duct margin are characteristic EUS features of early AIP, which has a more favorable prognosis, and shows a higher frequency of spontaneous remission and preservation of acinar cells, than advanced AIP.