If there are symptoms, the following may indicate colon cancer: 1  Abdominal pain and tenderness in the lower abdomen. 2  Blood in the stool. 3  Diarrhea, constipation, or other change in bowel habits. 4  Narrow stools. 5  Weight loss with no known reason.
Diarrhea may be caused by: lactose intolerance. bacterial infection. damage to intestinal wall. hormone-producing tumors (including certain types of pancreatic neuroendocrine tumors) inflammation or ulceration of the bowel. malabsorption caused by surgery that has shortened the intestines. pancreatic enzyme insufficiency.
Viruses (e.g., adenovirus, astrovirus, rotavirus, Norwalk virus) are the most common cause of diarrhea in the United States. The most common ones in children are rotavirus and in adults are norovirus. Escherichia coli, Clostridium difficile, and Campylobacter, Salmonella, and Shigella spp. are common bacterial causes.