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Incidental finding in a patient admitted with a history of trauma to pelvis.
Figure 1 to 3 contains multiple axial sections of a contrast enhanced CT scan of abdomen. Figure 1:A hyperdense and homogenously enhancing lesion in the region of gastric antrum (arrow). Body of the pancreas is in normal position (arrow heads). Figure2A and 2B: The lesion has a well defined and serrated outline (arrow) and in close relation to gastric antrum. Figure 3:Head of the pancreas in normal position (arrow).
Ectopic pancreas is a congenital anomaly also referred as heterotrophic, accessory or aberrant pancreas. It is defined as pancreatic tissue that lacks its anatomic or vascular continuity with the main body of the gland . It is reported with an incident of .5% to 14% in autopsy series. Ectopic pancreas is commonly located in Duodenum (28%) Stomach (26%) Jejunum (16%) . It is also found in ileum, ileal and jejuna diverticula, Meckel’s diverticulum and rarely involve the gall bladder, bile ducts, umbilicus, fallopian tubes, mediastinum, esophagus, lymph nodes and mesentery [2,3]. Ectopic pancreas can develop from an anomalous separation of developing pancreatic anlagen, with bowel wall penetration and subsequent displacement with longitudinal growth of the intestinal wall, or it can be due to differentiation of totipotent endodermal cells of intestinal tract into pancreatic tissue . Aberrant pancreatic tissue usually is small and measures .5cm to 2.0 cm but can rarely reach up to 5cm in size. Most cases of ectopic pancreas are asymptomatic and majority are found incidentally . If the ectopic pancreatic tissue is functional it can be involved with the same inflammatory or neoplastic process as the normal pancreas. The complications of ectopic pancreas are pancreatitis, pseudocyst formation, intussusception, insulinoma and pancreatic cancer.They can present with clinical symptoms such as abdominal pain, bleeding and obstruction [1,2]. Ectopic pancreas can present as a submucosal mass and simulate tumors such as Gastrointestinal stromal tumors (GIST) and Lieomyoma . On barium contrast studies classical finding in ectopic pancreatic tissue is a submucosal mass with central umbilication . On CT scan they usually appear as well defined round or oval mass with smooth or serrated outline in the gastric antral wall, intestinal wall or involving the mesentery. Studies done on CT findings of ectopic pancreas had shown that enhancement pattern of the ectopic pancreas is variable and depends on the microscopic composition of the tissue . Three subtypes are described according to their histopathologic composition. Those composed predominantly of acini, predominantly of ducts and of mixed tissues. Lesions with predominantly pancreatic acini had shown homogenous enhancement pattern and the lesions with mixed composition of ducts and acini had shown heterogenous enhancement . Some CT features such as prominent enhancement of the overlying mucosa, its location, Long Diameter/ Short Diameter (LD/SD) ratio, growth pattern and lesion boarder are helpful in differentiating ectopic pancreas from GIST and Lieomyoma. Heterotophic pancreatic tissue usually demonstrates a LD/SD ratio more than 1.4 and commonly found in gastric antrum, 6cm from the pyloric canal. Enhancement of the overlying mucosa had shown to be characteristic of ectopic pancreas compared to other submucosal lesions . MRI scans with coronal and sagittal images are helpful in showing the ectopic pancreas separately from the pancreas proper. MR Cholangiopancreatography is able to demonstrate an ectopic duct within heterotopic pancreas. This feature is considered pathognomonic of ectopic pancreas and may preclude the need for surgical excision to establish a diagnosis .
References / Suggested Reading:
1.Kim JY, MD. Lee JM, MD. Kim KW, MD et al. CT findings on Emphasis on differentiation from gastrointestinal stromal tumor and leiomyoma. Radiology; Volume252: number 1.July 2009. 2.Lin LH, MD. Ko SF, MD, Chuang CC, MD et al: Retroperitoneal ectopic pancreas: Imaging findings.The British journal of Radiology. December 82(2009):e253-e255. 3.Mortele KJ, MD. Rocha TC, MD. Streeter LJ, MD. Taylor AJ, MD: Multimodality imaging of pancreatic and biliary congenital anomalies.Radiographics 2006;26: 715-731. 4.Silva AC. Charles JC. Kimery BD. Wood JP. Liu PT. MR Cholangiopancratography in the detection of symptomatic ectopic pancreatitis in the small bowel mesentry; AJR 2006: 287: W195-W197.