What are some causes of pancreatic fatty replacement?
Fatty replacement, either diffuse or focal, can be seen with older age, cystic fibrosis, diabetes mellitus, obesity, corticosteroid use, chronic obstruction of the pancreatic duct (such as by tumor or calculus), and prior pancreatitis. When focal, it can sometimes mimic a hypoattenuating pancreatic mass on CT. However, focal fatty replacement typically occurs in the anterior pancreatic head with a smooth well-demarcated border from a platelike or triangular higher attenuation area of fatty sparing in the posterior pancreatic head and uncinate process and generally remains stable over time. Furthermore, there is preservation of the normal pancreatic contour and lobular appearance of the parenchyma, and no additional features of malignancy such as ductal obstruction, vascular encasement, lymphadenopathy, or metastatic disease are seen. On MRI, regions of focal fatty replacement have intermediate-high signal intensity on in-phase T1-weighted images with loss of signal intensity seen on out-of-phase T1-weighted images.