Impact of a dilated main pancreatic duct in the expected remnant pancreas on the incidence of clinically significant remnant pancreatic lesion after resection of noninvasive and microinvasive intraductal papillary mucinous neoplasms.

Background: Partial pancreatectomies for intraductal papillary mucinous neoplasms (IPMN) often leave a dilated main pancreatic duct (MPD). However, its impact on the development of remnant pancreatic lesions is unknown.

Methods: Medical records of consecutive patients who underwent partial pancreatectomy for noninvasive or microinvasive IPMN with dilated MPD on preoperative imaging between April 2007 and March 2023 at two tertiary referral centers in Japan were retrospectively reviewed. A dilated remnant MPD (DRM) was defined as an MPD diameter of the expected remnant pancreas of ≥5 mm. The clinically significant remnant pancreatic lesion (CSRPL) was defined as a remnant pancreatic lesion which requires intervention.

Results: A total of 172 patients (106 males and 66 females) were analyzed. Preoperatively, 132 patients (76.7 %) had mixed-type IPMN and 40 (23.1 %) had main duct IPMN. Among them, 16 patients (9.3 %) had CSRPL at 1569 days (median; range, 120-5503 days) after the initial surgery. In the preoperative imaging analysis, 104 patients (60.5 %) had DRM. The univariate analysis revealed that high-grade or micro-invasive pathology (p = 0.013) was significantly associated with CSRPL, whereas DRM was inversely associated with CSRPL (p = 0.021). The multivariate analysis revealed that the trends of DRM (p = 0.002) and high-grade/micro-invasive pathology (p = 0.003) remained significant.

Conclusions: Leaving a dilated MPD did not increase but instead inversely associated with the incidence of CSRPL after IPMN resection. It was suggested that preserving the pancreas, including the dilated MPD, is oncologically safe if the lesion of interest can be resected.