Background: Main pancreatic duct (MPD) involvement in branch duct-type intraductal papillary mucinous neoplasms (BD-IPMNs) is a high risk finding for malignant IPMNs. However, discrepancies exist in the identification of MPD involvement between imaging findings and pathological diagnosis. The purpose of this study was to evaluate the diagnostic accuracy of preoperative assessment of MPD involvement in IPMNs using contrast-enhanced harmonic endoscopic ultrasound (CH-EUS). Methods: This study involved 166 consecutive patients with BD-IPMNs who underwent surgical resection. CH-EUS was used to evaluate the MPD involvement according to the presence of mural nodules (MN) that advanced into the MPD or involved the MPD. The CH-EUS findings were compared with the pathological findings. Additionally, we analyzed the risk factors for malignant BD-IPMNs using multivariate analysis. Results: A total of 77, 51, and 38 patients were pathologically diagnosed with low-grade or intermediate-grade dysplasia, high-grade dysplasia and invasive IPMNs, respectively. MPD involvement was diagnosed using CH-EUS (MPD-inv.-EUS) in 90 (54.2%) patients with a sensitivity, specificity and accuracy of 83.5%, 87.0% and 84.9%, respectively. The malignancy rate in patients with MPD-inv.-EUS was 71.6% (63/90). Multivariate logistic regression analysis showed that MPD-inv.-EUS (OR, 3.61; 95% CI:1.45–8.98), age (OR, 5.70; 95% CI: 1.47–22.2), cyst size (OR, 2.45; 95% CI:1.04–5.78) and MN size (OR, 7.05; 95% CI:2.48–20.0) were significant for malignant BD-IPMNs. Conclusions: MPD-inv.-EUS accurately represents the pathological involvement of IPMN and may be a useful predictor of malignant BD-IPMNs.
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