Ileosigmoid knot. These schematic illustrations indicate the four forms of knotting. The active ileum may rotate around the sigmoid colon in either a clockwise (A) or counterclockwise (B) direction. Much more infrequently, the sigmoid colon may act as the active loop and rotate in either a clockwise (C) or counterclockwise (D) direction around the ileum. Source: From Beck DE, Rombeau JL, Stamos MJ, Wexner SD, eds. The ASCRS Manual of Colon and Rectal Surgery. 1st ed. New York: Springer; 2009: 426. Reprinted here with permission.