Non-enhanced T1 weighted GE3D FS MRI
Abdominal imagingCase Type
Leonardo Giarraputo MD, Sergio Savastano MD, Silvia Ceccato MD, Elisa Chemello MD, Mariacristina Maturi MD, Caterina Zivelonghi MD.Patient
72 years, male; 50 years, male
Case 1. A 72-year-old man referred to our Department for an MRI of the upper abdomen to rule out a hepatic lesion detected by abdominal sonography performed in a private centre.
Case 2. A 50-year-old man investigated with an abdominal MRI for a renal angiomyolipoma.
Case 1. The head of the pancreas encircling the vena porta was incidentally detected on MRI (Fig. 1A). On a more caudal scan, at the level of the splenoportal junction, the uncinate process appeared normal (Fig. 1B). The bridge of the pancreatic tissue posterior to the vena porta did not show any abnormal signal intensity. The Wirsung duct was not dilated. Revision of an abdominal CT performed 7 years ago evidenced a similar finding (Fig. 2).
Case 2. MRI demonstrated a thin layer of a normal pancreatic tissue encompassing the proximal segment of the porta vein above the splenoportal junction (Fig. 3).
Development anomalies of the pancreas are not wholly elucidated. Pancreas embryogenesis is genetically determined by molecules promoting or inhibiting development and differentiation of exocrine and endocrine cells lines from the embryo foregut [1-3]. Morphogenesis misregulation results in an overgrowth of the pancreas (annular pancreas or pancreatic heterotopias), or, more rarely, in agenesia or hypoplasia of the pancreas .
The pancreas develops from two diverticula of the embryonic foregut approximately during the fourth gestational weeks [4-9]. The smaller ventral bud gives rise to the uncinate process and the posterior part of the pancreatic head whereas the larger dorsal anlagen gives rise to the tail, the body and the anterior part of the pancreatic head.
The final configuration of the pancreas is related to the counterclockwise rotation of the embryonic foregut; alternatively, Kin et al. hypothesized the dominant growth of the dorsal bud induces the passive dislocation of the ventral anlagen posteriorly to the duodenum before the two buds fuse at the seventh gestational week .
A circumportal annular pancreas (CPAP) is a normal findings in swine [4, 10, 11], but it was considered extremely rare in humans. After the first report by Sugiura et al. in 1987 , revision of radiologic series evidenced a prevalence of a CPAP of 1.1-2.5% in general population [4, 13, 14].
According to the relationship between the pancreatic bridge and the splenoportal junction the CPAP is distinguished in suprasplenic (Type A, the more frequent), infrasplenic (Type B) or mixed (Type C); the course of the main pancreatic duct can be retroportal (Type I, the most common), retroportal with pancreas divisum (Type II) ore anteroportal (Type III) .
The CPAP is asymptomatic and thus often underdiagnosed by radiologists. Anyway, it is challenging for the surgeon because technical difficulties in dissecting the vena porta, pancreaticojejunal reconstruction, and the high complication risk of a postoperative pancreatic fistula . Moreover, radiologists should always report any vascular anomalies, such as celiac trunk variants or an aberrant common or right hepatic artery, since they make additional difficulties to the surgeon.
A CPAP can be easily detected both by non-enhanced and contrast-enhanced CT or MRI [16-18], which demonstrate a normal pancreatic bridge encircling the portal vein. Contrast-enhanced imaging is mandatory to delineate the anatomic relationship between the CPAP and vessels; when detailed imaging of the main pancreatic duct is required, paracoronal and paraxial MRCPs are mandatory.
Written informed patient consent for publication has been obtained
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