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Answer: Necrotizing Pancreatitis
The extensive peripancreatic fluid make the diagnosis of pancreatitis but always remember to evaluate the glad itself for any areas of hypoenhancement. In this case much of the mid pancreas does not enhance normally (compare to the head and tail).
Why is it important? They tend to present sicker (although not in this case) and their course is much more prolonged and has worse outcomes. Delayed imaging after several days can be helpful to evaluate for pancreatic duct injury and infection which are not rare complications
Thorough reference: https://pubs.rsna.org/doi/full/10.1148/rg.345130012 (req Radiographics login).
Although the grading/characterization seems to get more and more complicated, Always look for poorly enhancing parenchyma, duct injury and air (infection) in any case of pancreatitis