Symptoms and Tests for Colon Cancer

Senior woman caring for sick husband in bed
Stages I, II, and III account for more than 70% of colon cancer diagnoses. Sarah Kastner / STOCK4B-RF/Getty

Colon cancer is a common form of cancer, and having inflammatory bowel disease (IBD) can increase the lifetime risk of developing colon cancer. The symptoms of colon cancer and IBD can be quite similar. Therefore, it is important to always get a change in bowel habits or any other new or unusual symptoms checked out by a doctor.


In some cases, by the time symptoms or signs of colon cancer are apparent, cancer has become advanced.

Even those people who have a low risk for colorectal cancer should have any of the following symptoms checked out by a doctor.

The symptoms of colorectal cancer include:

  • Change in bowel habits
  • Diarrhea, constipation, or feeling that the bowel does not empty completely
  • Bright red or very dark blood in the stool
  • Narrow stools
  • Gas pains, bloating, fullness, and cramps
  • Unexplained weight loss
  • Chronic fatigue
  • Vomiting

Screening Tests 

Several tests may be used to diagnose colorectal cancer. In addition to a physical exam (which may include a digital rectal exam) and an evaluation of general medical history, several other tests may be performed.

Sigmoidoscopy. A sigmoidoscopy is a way for a doctor to examine the last one-third of the large intestine, which includes the rectum and sigmoid colon. A flexible viewing tube with a lens and light source on the end, called a sigmoidoscope, is used. Looking through the eyepiece at the other end of the scope, the doctor can see the inside of the colon.

In this test, the doctor can check for cancer, abnormal growths (polyps) and ulcers. It is usually performed in the doctor's office and can take 15-30 minutes. Beginning at age 50, a sigmoidoscopy is usually performed every 3 to 5 years to screen for colorectal cancer. In people who are at a higher risk for colorectal cancer due to ulcerative colitis, family history of colorectal cancer, or familial polyposis, screening may be recommended starting at age 35.

Colonoscopy. A colonoscopy is a test to examine the inside of the colon, which can go beyond the areas a sigmoidoscopy can reach. This test uses a colonoscope, which is a flexible tube with lenses, a tiny TV camera and a light at the end. Through fiber-optic technology and a video computer chip, the colonoscope can scan the inside of the colon and transmit images to a video screen. An attachment at the end of the colonoscope may be used to take a biopsy of the tissue in the colon. If a polyp is found, it may be removed using a wire loop attachment on the colonoscope. Both biopsies and polyps will be sent to a laboratory for further testing. The colonoscopy procedure can take up to 1 1/2 hours and is performed in a hospital as an outpatient procedure. For colon cancer screening, a colonoscopy is recommended every 10 years after age 50 for people not at high risk.

Barium Enema A barium enema (also called a lower gastrointestinal series) is a special type of X-ray that uses barium sulfate and air to outline the lining of the rectum and colon. Barium sulfate is a chalky chemical that shows up as white on X-ray film. The barium is given in an enema, which is then 'held' inside the colon while X-rays are taken.

Intestinal abnormalities may appear as dark silhouettes or patterns along the intestinal lining on the X-ray. Air may be pumped into the colon to help sharpen the outline of the intestinal wall. A barium enema can be performed as an outpatient procedure, and usually takes about 45 minutes. The enema might be uncomfortable, but the X-rays are completely painless. A barium enema is used to check for polyps (abnormal growths on the intestinal lining), diverticulosis, tumors, or other abnormalities. Beginning at age 50, a barium enema may be recommended once every 5 to 10 years instead of a colonoscopy for people not at high risk.

Biopsy. A biopsy is a sample of a small amount of tissue or cells that will be examined in a laboratory. During a colonoscopy, several biopsies (each at different locations in the colon and rectum) may be taken. They are commonly used to diagnose cancer or estimate how far cancer has spread. A biopsy is used to obtain bits of tissue to be checked in the laboratory for signs of cancer or other diseases. The biopsy sample is stained and examined under a microscope in the lab. This close examination can help the laboratory technician to determine if the sample is normal, part of a non-cancerous (benign) tumor, or a cancerous (malignant) tumor.

The Future of Screening

For those who cringe at the thought of a colonoscopy, there is hope on the horizon. New tests are being developed, but don't use that as an excuse to skip out on the doctor. Keep those colonoscopy appointments! It's the best way to catch colon cancer early. Caught early, colon cancer is curable.