Sclerosing meseneritis is idiopathic, chronic inflammation of the mesentery. The specific cause is unclear but there are associations with surgery, trauma, autoimmune disorders, vasculitis, infection, and malignancy.1 There can be a relation to IgG4 sclerosis disease.
There are subtypes based on the predominant histopathology, which are shown in their full spectrum in this case: Mesenteric panniculitis (inflammation) at presentation, and retractile mesenteritis (fibrosis) in the 3-year follow-up. This progression is not particularly common or necessarily expected, however.
Notice the narrowing of the SMV and formation of mesenteric and particularly impressive small bowel wall varices. Venous congestion likely accounts for the pronounced mucosal enhancement of the small bowel and ascites on both studies.