Colorectal cancer occurs when cells that line the large intestine and rectum develop genetic mutations. These mutations cause the cells to grow more normally than usual. Although colorectal cancer begins confined to one tumor, these cells may develop the ability to invade other areas of the body. These metastases can either move to other portions of the colon/rectum or can infiltrate other tissues.
General Symptoms
One of the hazards of colorectal cancer is its ability to spread. Colorectal cancer may spread to other portions of the colon and the rectum, or to other nearby organs. Many of the general (or constitutional) symptoms of metastatic colorectal cancer are shared by other forms of metastatic cancer. They include pain, either in the abdomen, pelvis or around the rectum, depending on the cancer's location. It may also cause extreme fatigue and weight loss that is coupled with a loss of appetite. Finally, metastatic cancer may also cause increased urinary frequency.
Symptoms of Spread Throughout The Colon
Because the colon and rectum are connected, the easiest site of spread of colorectal cancer is to other parts of the colon or to the rectum. If the cancer spreads to the right portion of the colon (which is the first part and is closest to the small intestine, large amounts of blood may appear in the feces, which can cause fatigue and anemia. Spread to the left portion of the colon (the end portion) can cause obstruction of the bowel, leading to constipation alternating with diarrhea. Streaks of blood may also appear in the feces. Spread to the rectum will cause bleeding during defecation as well as a feeling of incomplete emptying of the bowels.
Symptoms of Spread to Other Tissues
In some cases, colorectal cancer can spread outside of the colorectal system. The most common site for this is the liver. Liver metastases can cause yellowing of the skin and eyes (also known as jaundice). The liver may also become swollen (known as hepatomegaly), and fluid may accumulate in the abdomen. In severe cases, the patient will also develop problems with blood clotting. In addition to liver spread, colorectal cancer can also spread throughout the lymphatic system to the lymph nodes. The most common site for lymph node involvement is the supraclavicular lymph node, which will cause the formation of small hard lumps just above the collar bone.
