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.
1 Viruses such as the flu, norovirus, or rotavirus . Rotavirus is the most common cause of acute diarrhea in children. 2  Parasites, which are tiny organisms found in contaminated food or water.  Medicines such as antibiotics, cancer drugs, and antacids that contain magnesium.