Early colorectal cancer may have no obvious symptoms, but the following symptoms will appear only when the disease develops to a certain degree: 1. Change of bowel habit. Right half of colorectal cancer manifests as thin feces, pus and blood in the early stage, increase in the frequency of bowel movement, and diarrhea and constipation alternately; while left half of colorectal cancer manifests as difficulty in defecation, which will worsen as the disease progresses. Changes in stool character: thinning, bloody stool, mucus stool. Digestive tract symptoms: abdominal distension, discomfort or indigestion. In right half colon cancer, it is mostly discomfort or hidden pain in the right lower abdomen, which is very much like chronic appendicitis. Abdominal mass: About 50% of patients can find abdominal mass, which is a hard and irregular mass infiltrated by cancer or omentum and surrounding tissues, and the mass can be fixed due to the infiltration of cancer in late stage colon cancer. Blood or mucus in feces In right half colon cancer, the bleeding is small and fully mixed with feces due to peristaltic movement of colon, so it is not easy to be seen by naked eyes, but occult blood test is often positive; while in left half colon cancer, the bleeding and mucus are not mixed with feces, and about 1/4 patients can observe fresh blood and mucus in feces by naked eyes. Anemia and systemic symptoms such as lethargy, malaise, low fever.