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.
Diarrhea is sometimes caused by an infection in the stomach or intestines. It can also be caused by an inability to digest milk products (lactose intolerance), by problems with the pancreas, or by emotional stress. Bacteria, parasites, fungi, or viruses can cause the infection.1  Parasites: The parasites cryptosporidium or microsporidium used to cause diarrhea in many people with HIV. 2  Antiretroviral Medications: These can cause diarrhea. 3  Other causes: Taking antibiotics can kill off good bacteria in your gut and may cause diarrhea.t can also be caused by an inability to digest milk products (lactose intolerance), by problems with the pancreas, or by emotional stress. Bacteria, parasites, fungi, or viruses can cause the infection. 1  Parasites: The parasites cryptosporidium or microsporidium used to cause diarrhea in many people with HIV.