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.
A few of the more common causes of diarrhea include the following: 1  Bacterial and viral infections. 2  Food intolerance. 3  Medicine Diarrhea can be a side effect of many medicines, particularly antibiotics.  Intestinal diseases such as inflammatory bowel disease or celiac disease.