The bulging pancreas: unmasking causes beyond autoimmunity-an imaging-based approach to diffuse pancreatic enlargement.

Diffuse pancreatic enlargement is frequently attributed to autoimmune pancreatitis (AIP), but several benign, genetic, inflammatory, including acute interstitial edematous pancreatitis, and malignant entities can produce a similar imaging appearance. This review provides an imaging-based approach to recognize diffuse pancreatic enlargement, apply pragmatic measurement rules, and differentiate AIP from key mimics. Classic AIP imaging features (diffuse "sausage-like" morphology, capsule-like rim, long-segment duct narrowing without marked upstream dilation) and the value of clinical/serologic correlation and steroid response are emphasized. Key mimics reviewed include acute interstitial edematous pancreatitis, pancreatic lipomatosis, von Hippel-Lindau (VHL) disease, Mahvash syndrome, infiltrative adenocarcinoma, lymphoma, metastases, and diffuse neuroendocrine tumor, each with discriminating imaging and clinical clues. A structured assessment combining objective measurement, duct evaluation, enhancement pattern, systemic findings, and response to therapy after pancreatic malignancy has been reasonably excluded can reduce misdiagnosis of diffuse pancreatic enlargement and expedite appropriate biopsy or oncologic workup when indicated.