Hemolytic uremic syndrome (HUS) is a disease presenting with nonimmune hemolytic anemia, renal impairment and low platelet count. Escherichia coli serotype O157:H7 is the most common bacterial strain in typical HUS. Ulcerative colitis can be activated after E. coli infection and complications may occur afterwards. Toxic megacolon, necrosis and perforation of bowel, peritonitis, and severe hemorrhagic colitis are the complications of ulcerative colitis. In this paper, we report a typical Shiga toxin-associated HUS case accompanied by ulcerative colitis activation and toxic megacolon.