Circumportal Pancreas—a Must Know Pancreatic Anomaly for the Pancreatic Surgeon
Executive Summary
Circumportal pancreas (CirP) is a rare congenital anomaly characterized by the complete encasement of the portal vein (PV) and/or the superior mesenteric vein (SMV) by pancreatic tissue. Often asymptomatic and frequently overlooked during preoperative imaging, this condition presents significant challenges during pancreatic surgery, particularly pancreatic head resections. The primary clinical concern is a substantially increased risk of postoperative pancreatic fistula (POPF), with reported rates as high as 46.7%.
A retrospective study of 1,102 pancreatic head resections identified a CirP prevalence of 0.5%, though literature suggests a range between 1.14% and 2.5%. Crucially, preoperative CT and MRI/MRCP failed to identify the anomaly in 100% of the study’s cases, often misinterpreting retroportal tissue as tumor mass or inflammation. Pancreatic surgeons must maintain a high index of suspicion, particularly when encountering a replaced right hepatic artery arising from the superior mesenteric artery (SMA), which occurred in 67% of the study’s CirP cases. To mitigate the risk of fistula, surgeons should perform an additional resection of approximately 1 cm of the pancreatic body toward the tail to ensure a safe pancreaticojejunal anastomosis.
Overview and Embryology
Circumportal pancreas—also referred to as portal annular pancreas, retroportal pancreas, or complete pancreatic encasement of the portal vein—is a fusion anomaly. While other anomalies like pancreas divisum or annular pancreas are more common, CirP is notable for its potential to complicate major abdominal surgeries.
Embryogenesis
During the fourth week of development, two pancreatic primordia emerge from the primitive gut. By the sixth week, the ventral primordium rotates anticlockwise to fuse with the dorsal primordium, forming the uncinate process and the caudal part of the pancreatic head. CirP occurs when the uncinate process extends and fuses with the pancreatic body, effectively encasing the PV or SMV. The resulting main pancreatic duct (MPD) may be positioned either anterior (anteportal) or posterior (retroportal) to these major vessels.
Classification Systems
Clinical literature utilizes two primary classification systems to describe the morphological variations of CirP based on ductal course and relationship to the splenic vein.
Joseph et al. Classification (Ductal Course)
Karasaki et al. Classification (Vessel Relationship)
The most common variant is Joseph-Karasaki Type 3a (anteportal, suprasplenic), which accounts for 44.4% to 82% of cases in the literature.
Diagnostic Challenges
Preoperative identification of CirP is notoriously difficult. Cross-sectional imaging studies, including contrast-enhanced CT, T2-weighted MRI, and MRCP, often fail to depict the retroportal tissue clearly.
Findings from Clinical Data
Detection Rate: In a study of six confirmed cases, radiologists failed to correctly identify CirP in 100% of preoperative reports.
Misinterpretation: Retroportal tissue was variously misinterpreted as:
Tumor mass (leading to suspected neuroendocrine tumors or IPMN carcinomas).
Small, unremarkable rims of tissue.
Generalized atrophy or lipomatosis.
Inflammation masking the anomaly in cases of chronic pancreatitis.
PET-CT Limitations: In one case, retroportal pancreatic tissue showed increased FDG-uptake, leading to a false suspicion of a pancreatic neuroendocrine tumor.
Radiological "Red Flags"
A critical diagnostic indicator is deviant arterial anatomy. A replaced right hepatic artery arising from the SMA was present in 67% of patients with CirP in the analyzed cohort. The presence of this vascular variant should alert surgeons and radiologists to the possibility of a circumportal pancreas.
Surgical Implications and Management
CirP is typically discovered incidentally during surgery. Its presence necessitates significant alterations to standard pancreatic head resection techniques.
Technical Difficulties
Larger Resection Plane: The retroportal course of tissue requires dissection dorsal to the PV/SMV, creating an atypical and larger resection surface.
Complex Reconstruction: Pancreaticojejunal reconstruction must be performed partially dorsal to the major veins, which is technically demanding.
Vascular Proximity: Dissection occurs in close proximity to the celiac trunk and hepatic/splenic arteries, increasing the risk of intraoperative hemorrhage.
Mixed Type Complexity: Type C (mixed) cases are the most demanding, potentially requiring three separate pancreatic divisions.
Risk of Pancreatic Fistula
The technical difficulty of achieving a clear, safe resection margin leads to a high incidence of postoperative pancreatic fistula (POPF). Literature reports a POPF rate of up to 46.7% in CirP patients.
Management Strategies
Additional Resection: To ensure a secure anastomosis, it is recommended to perform an additional resection of the pancreatic body (approximately 1 cm) toward the tail. This moves the anastomosis site to a more distal, thinner segment of the pancreas where a safer pancreaticojejunostomy can be constructed.
Total Pancreatectomy (TP): In cases where the pancreatic tissue is extremely soft, the duct is decentralized/small, or the remaining pancreatic segment is shorter than 4 cm, a total pancreatectomy should be considered. This approach avoids the high-risk anastomosis entirely, particularly in patients who already have impaired endocrine function (e.g., insulin-dependent diabetes).
Conclusion
Circumportal pancreas is a rare but "must-know" anomaly for pancreatic surgeons. Its tendency to remain undetected on preoperative imaging places a premium on intraoperative vigilance. By recognizing associated vascular anomalies like a replaced right hepatic artery and employing strategic additional tissue resection, surgical teams can mitigate the substantial risks of postoperative morbidity and fistula formation associated with this condition.
