Natural History of the Remnant Pancreatic Duct after Pancreatoduodenectomy for Non-Invasive Intraductal Papillary Mucinous Neoplasm: Results from an International Consortium

Background: Little is known about the prognostic significance of pancreatic duct (PD) dilation following pancreatoduodenectomy for intraductal papillary mucinous neoplasms (IPMN). Although PD dilation is typically the hallmark radiographic feature of IPMN, other causes of PD dilation exist, including anastomotic stricture, pancreatitis, senescence, and postsurgical passive dilation. Therefore, PD dilation after pancreatoduodenectomy for IPMN represents a diagnostic and management dilemma. The purpose of this study was to evaluate the significance of PD dilation after pancreatoduodenectomy for noninvasive IPMN.

Methods: All patients who underwent pancreatoduodenectomy for noninvasive IPMN at nine pancreatic academic centers between 2013 and 2018 were included. Variables were entered prospectively into institutional databases and retrospectively reviewed for the purpose of this study. Dilation of the PD remnant was defined as a duct diameter of ≥5 mm, according to international guidelines.

Results: Four-hundred and eighty-one patients were included in this study. The mean age of the patients was 66 years (range 30-90). Patients were surveilled for a median of 4.5 (+/-2.3; max 10.6) years. During follow-up, 132 patients (27.4%) developed PD dilation in the remnant tissue after a median of 3.3 years. Multivariable analysis demonstrated that older age at the time of pancreatoduodenectomy (P=0.01) and longer surveillance duration (P=0.002) were predictors of PD dilation. Interestingly, neither the pathological IPMN subtype (branch-duct vs. main duct/mixed, P=0.96) nor the preoperative PD diameter (P=0.14) was associated with an increased risk of PD dilation in the remnant. During follow-up, IPMN recurrence was suspected in the remaining 72 patients (18.4%), solely because of ductal dilation on cross-sectional imaging in 97% (70/72). Completion pancreatectomy was performed in only 16 patients (3.3%), of whom only four (0.8%) had invasive carcinoma. Three of these four patients had high-grade dysplasia in the original pancreatoduodenectomy specimen, whereas only one had a low-grade dysplastic lesion initially. On multivariable analysis, no variable was predictive of IPMN recurrence in the remnant.

Conclusions: New main duct dilation in the pancreatic remnant after pancreatoduodenectomy for IPMN is common, occurring in 27% of the patients. The duration of surveillance is the main factor associated with remnant PD dilation, suggesting that this is likely a physiologic phenomenon. Although recurrence of IPMN in the remnant is often suspected, only 0.8% of patients develop an invasive carcinoma in the pancreatic remnant requiring completion pancreatectomy.