Retroportal main pancreatic duct with circumportal pancreas: radiographic visualization

PurposeThe aim of this study was to investigate the imaging findings of retroportal main pancreatic duct (RMPD), a rare anomaly of the pancreas, and circumportal pancreas (CP) on computed tomography (CT) and magnetic resonance (MR) imaging. We also reviewed the previous literature and discussed its best imaging method, etiology and clinical importance.MethodsThis work is a retrospective study. Two cases of RMPD were enrolled. The imaging findings of RMPD and CP were reviewed among the various CT and MR images obtained. Differences in visualization among the scans were evaluated using a four-stage model.ResultsRMPD was always accompanied by CP. RMPD was detectable on contrast-enhanced CT but not on noncontrasted CT. RMPD was shown most clearly on arterial, portal and late phases of contrast-enhanced CT, contrast-enhanced fat-suppressed T1-weighted images and fat-suppressed T2-weighted images. CP was much easier to detect than RMPD and could be identified even on noncontrasted images.ConclusionsWe described the fourth and the fifth reported cases of RMPD. This is the first study to describe its MR imaging findings. CP was always present in cases of RMPD and was easily detectable on tomographic images. When radiologists or surgeons notice CP, it is necessary to pay attention to the course of the main pancreatic duct, particularly preoperatively to avoid surgical complications. It should be noted that these anomalies are undetectable on projection images.