Changes in bowel movements, such as diarrhea or constipation, or change in consistency or size of stoolsFeeling that the bowel has not emptied completely after a bowel movementAbdominal discomfort such as gas, bloating, and crampsRectal bleeding or blood in stoolPain when having a bowel movementUnexplained weight lossUnexplained iron-deficiency anemia (low red blood cell count)Weakness and fatigue