How is colorectal cancer diagnosed?

Colorectal cancer is often found after symptoms appear, but most people with early colon or rectal cancer don't have symptoms of the disease. Symptoms usually only appear with more advanced disease. This is why getting the recommended screening before any symptoms develop is so important.

If your doctor finds something suspicious during a screening exam, or if you have any of the symptoms of colorectal cancer described below, your doctor probably will recommend exams and tests to find the cause. Colorectal cancer may cause one or more of the symptoms below. If you have any of the following you should see your doctor:

A change in bowel habits, such as:

• diarrhea
• constipation
• narrowing of the stool that lasts 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
• blood in the stool (often, though, the stool will look normal)Cramping or abdominal (stomach area) pain
• Weakness and fatigue
• Unintended weight loss

Doctors will perform a fecal occult blood test to detect any blood in the stool. If blood is found, your physician will most likely perform a colonoscopy or sigmoidoscopy to examine the colon and determine the cause of bleeding.

Both procedures use an endoscope, a flexible tube equipped with a light and camera that is inserted into the rectum and guided into the colon. A colonoscopy is more comprehensive. It can examine the rectum and entire colon, but requires greater preparation on the part of the patient and the use of sedation. Preparations may include a liquid diet several days prior to the procedure, a laxative the night before, and an enema the day of the procedure. Alternatively, a sigmoidoscopy requires less preparation, usually just an enema the day of the procedure, and can be done without sedation. But the procedure is also less comprehensive and can examine only the rectum and the bottom two feet of the colon.

Physicians may also couple a sigmoidoscopy with another procedure known as a double-contrast barium enema. With this, barium is infused into the rectum via an enema tube and an x-ray is taken of the area. The barium helps produce a clearer, more detailed x-ray of the area.

A number of other imaging tests such as ultrasound exams and computed tomography (CT or CAT) scan may be used to visualize organs and see if cancer is present.

To diagnose colorectal cancer (CRC) a gastroenterologist (medical GI specialist) or surgeon usually will perform a colonoscopy in order to visualize the entire colon directly. After giving medicine to sedate the patient, the GI specialist or surgeon inserts a thin, flexible fiberoptic scope through the anus into the rectum. Ideally, the entire lining of the colon is inspected. Biopsy of any suspicious lesions, masses, or polyps is performed during this procedure. Most CRCs are adenocarcinomas. Other types of cancer in the colon or rectum are rare.

The third leading cause of cancer deaths, most colorectal cancers arise from lesions on the intestinal lining called adenomatous polyps. The progression from precancerous polyp to full-blown cancer is believed to take 10 years or more, though. Screening allows physicians to remove polyps before they become cancerous and to identify cancer early, when it's most treatable.

Colonoscopy is recommended as a screening test at age 50 for women at average risk and then every decade thereafter. (If you have a family history, inflammatory bowel disease, or other factors, you may need more frequent screening.) During a colonoscopy, a gastroenterologist examines the lining of the colon with a lighted scope, looking for cancerous lesions and polyps.

There are other screening methods -- fecal occult blood testing, flexible sigmoidoscopy, computed tomography (CT) colonography (virtual colonoscopy), and a stool test for DNA shed by colorectal cancers -- but traditional colonoscopy is preferred because it checks the entire colon, finds the most polyps and lesions, and allows the doctor to biopsy or remove polyps and lesions during the procedure. Colonoscopy is particularly important for women, who are more likely to have polyps or lesions deeper in the ascending colon, the area at the farthest reach of the colonoscope. In contrast, sigmoidoscopy examines only the first third of the colon.

Colorectal cancer is diagnosed by biopsy. The most common way today is that a patient has a screening colonoscopy, a polyp is detected and a biopsy is performed. Microscopic analysis reveals the result to be colon cancer. Sometime colorectal caner is found on barium enema or sigmoidoscopy. By the time the patient presents with symptoms, usually the cancer is quite advanced.

Tests to help your doctor see if colorectal cancer has spread or come back include:

• An abdominal ultrasound to find the cause of pain or swelling in your abdomen.
• A colonoscopy to see if cancer has returned to your intestine.
• Blood tests to find out if cancer has returned (CEA) or to find the cause of symptoms such as weakness, fatigue, fever, bruising or weight loss (complete blood count).
• A chest X-ray to find the cause of symptoms such as persistent coughing, coughing up blood, chest pain or difficult breathing.
• A computed tomography (CT) scan, magnetic resonance imaging (MRI), or positron emission tomography (PET) scan to see if colorectal cancer has spread into the chest or organs in the abdomen or pelvis.
• A brain CT scan or MRI to look into symptoms such as confusion, paralysis, numbness, vision problems, vertigo or headaches.
• A biopsy, such as a liver biopsy or a lung biopsy, to find out where the cancer cells have spread.
• A bone scan to find out whether cancer cells have spread to the bones.

What to think about - Colorectal cancer often comes back, even after treatment that seemed successful. If you had colorectal cancer in the past, pay close attention to your body and see your doctor regularly. Tell your doctor about any changes, such as decreased appetite, bloating or an increase in the size of your belly. Your cancer may return even if you do everything you can to prevent it. If this happens, focus on what you and your doctor can do to treat your symptoms to help you feel better and live longer.