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 acute diarrhea include: 1  Viral infections, such as the stomach flu. 2  Bacterial infections, such as those involving Salmonella typhi or E. coli. 3  Parasites, such as Giardia. 4  Medicines, such as antibiotics. 5  Anxiety.