Mesenteric panniculitis (also referred to as sclerosing mesenteritis) is an uncommon lesion in which there is diffuse or nodular thickening of the mesentery. Grossly, it results in distortion and twisting of loops of bowel due to formation of adhesions (as depicted in this photograph). Microscopically, the thickened areas of the mesentery show prominent fibrosis, chronic inflammation, and fat necrosis. The blood vessels may show signs of vasculitis and thrombosis. At least some of the cases of mesenteric panniculitis are thought to represent lymphomas with prominent sclerosis disguised as a chronic inflammatory condition. Other lesions that enter into the differential diagnosis include: fibrosis that may be seen around colorectal carcinomas and diverticulitis, Whipple disease, and idiopathic retroperitoneal fibrosis.