Skip Navigation Bar
NIH MedlinePlus the Magazine, Trusted Health Information from the National Institutes of Health

Special Section:
Colorectal Cancer

Colorectal Cancer:
Symptoms, Diagnosis and Treatment


Check with your healthcare provider if you have any of the following symptoms:

  • A change in bowel habits, such as diarrhea, constipation, or narrowing of the stool, that lasts for more than a few days
  • A feeling that you need to have a bowel movement that is not relieved by doing so
  • Rectal bleeding, dark stools, or blood in the stool
  • Cramping or abdominal (belly) pain
  • Weakness and fatigue

Most of these symptoms are more likely to be caused by conditions other than colorectal cancer, such as infection, hemorrhoids, or inflammatory bowel disease. Still, if you have any of these problems, it's important to see your healthcare provider right away so the cause can be found and treated, if needed.


Health care providers may suggest one or more of the following tests for colorectal cancer screening:

  • Fecal occult blood test (FOBT)—This test checks for hidden blood in fecal material (stool).
  • Sigmoidoscopy—In this test, the rectum and lower colon are examined using a lighted instrument called a sigmoidoscope. During sigmoidoscopy, precancerous and cancerous growths in the rectum and lower colon can be found and either removed or tested.
  • Colonoscopy—In this test, the rectum and entire colon are examined using a lighted instrument called a colonoscope. During colonoscopy, precancerous and cancerous growths throughout the colon can be found and either removed or tested.
  • Virtual colonoscopy (also called computerized tomographic colonography)—In this test, special x-ray equipment is used to produce 3-D pictures of the colon and rectum. A computer then assembles these pictures into detailed images that can show polyps and other abnormalities. (see page 9)


Different types of treatment are available for patients with colon cancer. Three types of standard treatment are used: surgery, chemotherapy and radiation therapy.

  • Surgery (removing the cancer in an operation) is the most common treatment for all stages of colon cancer.
  • Chemotherapy is a cancer treatment that uses drugs to stop the growth of cancer cells, either by killing the cells or by stopping them from dividing. When chemotherapy is taken by mouth or injected into a vein or muscle, the drugs enter the bloodstream and can reach cancer cells throughout the body (systemic chemotherapy). When chemotherapy is placed directly into the spinal column, an organ, or a body cavity such as the abdomen, the drugs mainly affect cancer cells in those areas (regional chemotherapy).
  • Radiation therapy is a cancer treatment that uses high-energy x-rays or other types of radiation to kill cancer cells or keep them from growing. There are two types of radiation therapy. External radiation therapy uses a machine outside the body to send radiation toward the cancer. Internal radiation therapy uses a radioactive substance sealed in needles, seeds, wires, or catheters that are placed directly into or near the cancer.

Colorectal cancer is a disease in which malignant (cancer) cells form in the tissues of the colon or the rectum. The colon is part of the body's digestive system.

Illustration of colonic  polypsDiagram of the human digestive tract

Click on the image for a enlarged version

NIH Research to Results

The NIH's National Cancer Institute (NCI) is the world's largest organization solely dedicated to cancer research. NCI supports researchers at universities and hospitals across the United States. It also supports NCI-Designated Cancer Centers, a network of facilities that not only study cancer in laboratories but also conduct research on the best ways to rapidly bring the fruits of scientific discovery to cancer patients.

  • The drug fluorouracil (5-FU) has been part of chemotherapy treatment for stage II and III colon cancer for several decades. Studies have shown that this treatment improves overall survival, but not the risk of the cancer occurring again.
  • Results from a phase III clinical trial indicate that low doses of two chemopreventive agents—an anti-inflammatory and an experimental compound—are very effective at preventing the recurrence of the lesions that are often a sign of colorectal cancer. The results showed that the treatment was most effective in preventing the recurrence of the highest-risk polyps, showing a 92 percent reduction.
  • The American College of Radiology Imaging Network (ACRIN) National CT Colonography Trial has found that computerized tomographic (CT) colonography, also known as virtual colonoscopy, is comparable to standard colonoscopy. The ACRIN trial, sponsored by NCI, is the largest multi-center study to compare the accuracy of state-of-the-art CT colonography to the gold standard of conventional colonoscopy.

Questions to Ask Your Doctor


  • When do I need to have a colonoscopy?
  • How often should I get a colonoscopy?
  • What are my risk factors for colon cancer?
  • What can I do to reduce my risk of getting colon cancer?
NLM Staff member David Nash and Senator Daniel InouyeDavid Nash dunking the basketball

Photos: David Nash

Former Globetrotter Star Recommends Early Screening

Former Harlem Globetrotter David Nash, currently a staff member at the National Library of Medicine, was recently diagnosed with early-stage colon cancer, after a timely colonoscopy.

Nash is pictured with U.S. Sen. Daniel Inouye of Hawaii, chair of the Senate Appropriations Committee and a long-time champion of medical research.

Because Nash caught the colon cancer early, chances for recovery are excellent.

Read More "Colorectal Cancer" Articles

Preventing, Detecting, and Treating Colorectal Cancer / A Conversation with Katie Couric / Colorectal Cancer: Symptoms, Diagnosis, Treatment / New Ways to Detect Colon Cancer

Spring 2009 Issue: Volume 4 Number 2 Pages 7 - 8