Constipation, diarrhea, blood in the stool, persistent gas, cramps or pain, and a feeling that the bowel isn't emptying completely are gastrointestinal symptoms of colorectal cancer, states Mayo Clinic. People with colorectal cancer may also suffer from unexplained weight loss and fatigue.
When cancer is present in the last several inches of the colon, it is referred to as rectal cancer, while colon cancer occurs in other parts of the large intestine, notes Mayo Clinic. The two are referred to as colorectal cancers, many of which start as small clumps of polyps that cause no symptoms. Doctors recommend screening for colon cancer so they can identify and remove these polyps before they become cancerous. People experience various symptoms of colorectal cancer depending on where it is located in the large intestine and the size of tumors.
Doctors do not know what causes colorectal cancer, as of 2015; however, people over the age of 50, African-Americans, those with family histories of colon cancer and people with inflammatory intestinal conditions such as Crohn's disease are at higher risk, according to Mayo Clinic. Doctors have also linked heavy alcohol use, smoking, obesity and an inactive lifestyle with the disease. There are four stages of colorectal cancer, depending on where it is located and how far it has spread into other parts of the body.