Usefulness of Endoscopic Ultrasonography (Plain Combined with Contrast-Enhanced) in the Differentiation Between Autoimmune Pancreatitis and Pancreatic Cancer

Abstract

Objectives: Autoimmune pancreatitis (AIP) is a unique form of chronic pancreatitis, and we need to differentiate it from pancreatic cancer (PCA) in the process of diagnosis. Endoscopic ultrasonography (EUS) is known as a useful examination in pancreato-biliary field, but reports on EUS findings with AIP are limited. The aim of this study is to investigate the usefulness of EUS (plain combined with contrast-enhanced) in the differentiation between AIP and PCA. Methods: We reviewed 36 patients with AIP (male: female=33: 3, mean age 62.9) based on the criteria established by Japan Pancreas Society in 2006 between July 2003 and October 2008 and 36 patients with PCA (male: female=24: 12, mean age 61.6) based on pathological diagnosis between April 2005 and October 2008. All patients underwent EUS, and we investigated 6 findings as follows; location, internal echo, border with surroundings, upstream dilation of main pancreatic duct (MPD), wall thickness of bile ducts, and lymph nodes enlargement. Contrast-enhanced EUS (CE-EUS) using Perflubutane (Sonazoid™, Daiichi-Sankyo, Japan) was performed for 16 patients with AIP and 20 patients with PCA, and enhancement effects and diagnostic capability of CE-EUS were evaluated. Enhancement effects compared with surrounding pancreatic parenchyma were observed for 1 minute continuously, and 3 minutes, 5 minutes after injection of contrast medium, and were classified into 3 patterns as follows using time intensity curve; pattern A (pA): Equal enhancement effect continued for 5 minutes, pattern B (pB): Equal enhancement effect continued for 1 minute, and decreased after 3minutes, pattern C (pC): Enhancement effect decreased within 1 minute. (Results) The locations of the lesions of AIP and PCA were, head: body and tail: whole body = 18 (50%): 5 (13.9%): 13 (36.1%) and 25 (69.4%): 11 (30.6%): 0 (0%). All lesions were hypoechoic, and stripe or mesh hyperechoic areas were seen only in AIP (16.6% (6/36), 6% (2/36)). Anechoic areas were seen only in PCA (25% (9/36)). The incidence of clear borders was higher in PCA (19.4% (7/36): 83.3% (30/36)) (p<0.001). The diameter of upstream MPD was more increased in PCA (2.89: 5.06 (mm)) (p=0.007), and the incidence of wall thicknesses of bile ducts was higher in AIP (63.6% (7/11): 11.1% (2/18)) (p=0.01). There was no significant difference in lymph nodes enlargement. Enhancement patterns of AIP and PCA were, pA: pB: pC= 12 (75%): 2 (12.5%): 2 (12.5%) and 0 (0%): 5 (25%): 15 (75%). Judging the pB or pC as PCA, the sensitivity, specificity, and accuracy rate of CE-EUS were 75%, 100%, and 88.9%. Conclusions: EUS combined with CE-EUS is useful for differentiating AIP and PCA.