Portal annular pancreas: a rare surgical challenge

A 62-year-old female underwent pancreaticoduodenectomy (PD) for ampullary adenocarcinoma. Preoperative imaging showed a replaced right hepatic artery (RHA) from the superior mesenteric artery and a left hepatic artery from the left gastric artery. Intraoperatively, pancreatic tissue encircled the portal vein (PV). CT revealed a dilated anteportal main pancreatic duct (MPD). The ventral pancreatic neck was divided with diathermy, and the dorsal pancreas was stapled while protecting the RHA. She developed a grade A postoperative pancreatic fistula (POF) and intermittent fevers, with a 3.2 cm collection that resolved without intervention. A 64-year-old male underwent distal pancreatectomy (DP) and splenectomy for pancreatic body ductal adenocarcinoma invading the splenic vein and encasing the splenic artery. After stapling the pancreatic neck, pancreatic parenchyma extended behind the portal vein and fused with the pancreatic head. Retrospective review of cross-sectional imaging showed a portal annular pancreas (PAP) with a retroportal MPD. The dorsal pancreas was divided with a stapler, creating two resection planes. The patient developed a grade A POPF but recovered well (Figs. 1-3). PAP is a rare and asymptomatic congenital anomaly (0.8%–2.5% prevalence) characterised by fusion of the ventral and dorsal pancreatic buds around the PV.1 It is often overlooked on imaging and has only been reported 53 times in pancreatic surgery since it was first described by Sugiura et al. in 1987.1, 2 However, it is important to be aware of it due to an increased risk of clinically relevant POPF (CR-POPF) of up to 34%.1 Vascular injury risk may also be increased when PAP coexists with vascular anomalies, as in our PD patient.3 The elevated POPF risk stems from challenges posed by specific PAP subtypes and the surgical strategies used to address them, compounded by its tendency to be an unexpected intra-operative finding.4 Joseph et al. classified PAP by the MPD's relationship to the PV: retroportal (type 1), associated with divisum (type 2) or anteportal (type 3).5 Karasaki et al. classified PAP based on the location of the fused pancreas relative to the splenic vein: suprasplenic (type A), infrasplenic (type B) or mixed (type C).6 These classifications are frequently combined when reporting PAP, for example, as type 3A and 1A in our case above.1 Preoperative recognition of PAP on CT should prompt an MRCP to delineate the specific type.1 Surgical strategy should be tailored to the type of PAP. Type 3A is the most common (up to 92%) and the most straightforward surgically.3 During PD, stapled division of the dorsal pancreas is most common but is associated with a 71% CR-POPF rate, compared to 16% with extended resections.1 This increased risk may be due to a missed retroportal duct.5 In our PD case, stapled division did not result in CR-POPF. Extended resection should be considered when the MPD is retroportal to facilitate a safe anastomosis but may be hazardous in type C PAP, where the pancreas is fused around both the PV and SMV.1, 4 Some advocate joining both resection planes into a pancreaticogastrostomy to minimise exocrine and endocrine dysfunction rather than an extended resection.7 Few DP cases are reported compared to PD, limiting conclusions.1 The pancreas is thicker at the site of fusion, increasing the risk of parenchymal fracture with stapling and subsequent POPF.8 When distal division is not feasible, the ventral and dorsal pancreas should be divided separately at the neck to minimise this risk. PAP is an underappreciated anatomical variation with significant surgical implications. Preoperative recognition and tailored surgical strategies may reduce the risk of CR-POPF. Written informed consent was obtained from both patients for the publication of this case report and the accompanying images. No additional ethical approval was required for this publication.