Su1345 Usefulness of Contrast-Enhanced Harmonic Endoscopic Ultrasonography for Identification of Mural Nodules in Intraductal Papillary Mucinous Neoplasms

Abstract

OBJECTIVES: Although recent studies have reported that presence of mural nodules (MNs) is one of the associated predictors of malignancy in intraductal papillary mucinous neoplasms (IPMNs), it is sometimes difficult to discriminate MNs from mucus clots (MCs) on fundamental B-mode EUS (FB-EUS). Contrast-enhanced harmonic EUS (CH-EUS) is useful to discriminate MNs from MCs because CH-EUS clearly depicts vascular flow of a MN. The present study aimed to elucidate diagnostic ability to discriminate MNs from MCs in IPMNs. METHODS: For this study, 113 patients with IPMN, who underwent contrast-enhanced CT (CE-CT), FB-EUS and CH-EUS before surgical resection between November 2008 and December 2015, were analyzed. On CE-CT, a MN was defined as a solitary lesion that showed enhancement in a main pancreatic duct (MPD) or a cyst of the pancreas. On FB-EUS, a MN was defined as a EUS-detectable protrusion of a MPD or a cyst wall of the pancreas into its lumen. On CH-EUS, a MN was defined as a MPD or a cyst wall protrusion of the pancreas that showed enhancement after contrast administration. Presence of MNs was confirmed by histopathological examination of specimens obtained by surgical resection. Values for diagnostic ability in identification of MNs were compared among CE-CT, FB-EUS and CH-EUS. RESULTS: Final diagnoses were main duct IPMN in 12 patients, branch duct IPMN in 57 patients and mixed type in 44 patients. Sensitivity, specificity and accuracy for identification of MNs were 69 %, 92 %, 80 % in CE-CT, 92 %, 82 %, 88 % in FB-EUS and 92 %, 94 %, 93 % in CH-EUS. While sensitivity for identification of MNs with FB-EUS (92 %) was higher than with CE-CT (69 %), specificity with FB-EUS (82 %) was lower than with CE-CT (92 %). In contrast, specificity with CH-EUS (94 %) is higher than with FB-EUS (82 %). There were 9 false-positive cases on FB-EUS, while CH-EUS successfully excluded MNs in 6 of them. There were 19 false-negative cases on CE-CT, while CH-EUS successfully detected MNs in 14 of them. Diagnostic accuracy of CH-EUS for identification of MNs was the highest of all three modalities and was significantly higher than that of CE-CT (p＝0.005, McNemar test). CONCLUSIONS: CH-EUS is a useful tool for identification of MNs in IPMNs, and is considered more accurate than FB-EUS and CE-CT.