1 Sclerosing Mesenteritis: A rare disorder that affects the lining of the digestive tract. 2  The lining of the small bowel mesentery (membrane that joins small intestine to back of abdominal wall) becomes thickened and inflamed.3  The condition may be mild or severe enough to cause death. Sclerosing Mesenteritis: A rare disorder that affects the lining of the digestive tract. 2  The lining of the small bowel mesentery (membrane that joins small intestine to back of abdominal wall) becomes thickened and inflamed. 3  The condition may be mild or severe enough to cause death.