S3664 Extensive Enlargement of the Pancreatic Head and Uncinate Process: An Overlooked Anatomical Variant With Clinical Implications

Introduction: Extensive enlargement of the pancreatic head and the uncinate process is an exceedingly rare and underrecognized anatomical variant, with rare documentation in current medical literature. It is hypothesized to result from excessive fusion or disproportionate growth of the ventral and dorsal pancreatic buds during embryogenesis. Such extensions may encase or displace adjacent retroperitoneal organs and neurovascular structures, mimicking mass lesions or creating potential sites for internal herniation. We present 2 radiologically confirmed cases of this entity discovered incidentally in asymptomatic individuals undergoing pancreatic screening. Case Description/Methods: Two unrelated, asymptomatic middle-aged women with a family history of pancreatic cancer underwent screening abdominal imaging. Cross-sectional imaging revealed extensive enlargement of the pancreatic head and uncinate process in both patients. The pancreatic tissue wrapped around several retroperitoneal structures including the anterior walls of the second and third parts of the duodenum (resulting in C-loop widening and mild luminal narrowing), the common bile duct, anterior aortic surface, inferior vena cava, superior mesenteric vessels, and extended up to the right renal upper pole. Importantly, the enlarged tissue demonstrated isointense on all magnetic resonance imaging sequences, no abnormal contrast enhancement, and homogeneity with the rest of the pancreatic parenchyma. One case showed stable imaging findings over a 5-year interval, favoring a benign, nonneoplastic anatomical variant. Discussion: These cases raise important considerations regarding the embryological origins, clinical implications, and diagnostic challenges posed by this rare pancreatic variant. Recognizing such anatomical variants is critical for radiologists to avoid false-positive interpretations, for gastroenterologists and pancreaticobiliary specialists to consider when evaluating duodenal compression or atypical abdominal symptoms, and for surgeons or interventionalists to avoid iatrogenic injury. As current literature remains limited, these cases highlight the need for further research into the incidence, clinical course, and long-term implications of extensive pancreatic head and uncinate process enlargement.