Definition
Colorectal cancer, also called colon cancer or cancer of the large bowel, includes cancerous growth in the colon and rectum. Many colorectal cancers are thought to arise from adenomatous polyps in the colon. The diagnosis of localized colorectal cancer is through colonoscopy. Therapy is usually through surgery, which in many cases followed by oncologic treatment (chemotherapy).

Symptoms
The symptoms of colorectal cancer depend on the location of tumor in bowel. Most of symptoms may occur in other diseases as well. Symptoms and signs are classified into local, general (affecting the whole body) and caused by spread of other organs (metastasis).

Local symptoms include:
• Change in bowel habit (new-onset diarrhoea or constipation)
• Reduction in diameter of stool
• Feeling of incomplete defecation
• Lower gastrointestinal bleeding, including the passage of bright red blood in the stool
• Atypical abdominal pain

General symptoms include:
• Iron deficiency anemia (caused by chronic occult bleeding)
• Fatigue
• Pallor
• Weight loss
• Loss of appetite

Metastatic symptoms include:
• Liver enlargement (cancer spreads to the liver)
• Jaundice, pale stools (the tumor invades the bile duct)

Diagnosis
Colorectal cancer can take many years to develop and early detection of colorectal adenomas and colorectal cancer greatly improves the chances of a cure. Therefore, colorectal cancer screening is recommended in all individuals who are at increased risk and in subjects aged over 50 years.
Colonoscopy is the gold standard for the diagnosis and for screening. A lighted probe called a colonoscopy is inserted into the rectum and the entire colon to look for adenomas (polyps) and other abnormalities that may be caused by colorectal cancer. Colonoscopy has the advantage that if polyps are found during the procedure they can be immediately removed. In addition, tissue can also be taken for biopsy; the tissue sample is then tested with a microscope.