Sclerosing Mesenteritis. Sclerosing mesenteritis is a rare disease that affects a fold of tissue that connects the small bowel to the wall of the abdomen. This fold is called the small bowel mesentery. Inflammation and scarring (fibrosis) of the small bowel mesentery are the main features of sclerosing mesenteritis.inding the cause has been difficult, but it is thought that patients with sclerosing mesenteritis have had abdominal surgery or trauma to the abdomen. They also may have autoimmune diseases in which the body produces an inappropriate immune response to its own tissues and substances.