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An elderly man who refuses colonoscopy

Julie Vajnar, PA-C, RT

Julie Vajnar is the department editor for Diagnostic Imaging Review and practices in a radiology group at North Oaks Health System, Hammond, Louisiana. She has indicated no relationships to disclose relating to the content of this article.

CASE

An 81-year-old male presented to the office with complaints of frequent constipation that represented a change from his usual bowel habits. Normally, he had 4 to 5 bowel movements per week, but over the past few months he had only 1 or 2 per week. He also noted that the stool was of smaller caliber than normal. He denied any recent weight loss, smoking, or alcohol use, but he did smoke 30 years ago. He had not changed his diet or traveled recently. The only new medication he was taking was a laxative, which he stated was not helping. A digital rectal examination was negative, but a test for occult blood in the stool was positive. When the need for colonoscopy was discussed with the patient, he refused, stating he was afraid to undergo anesthesia, and wanted to know what else could be done. A barium enema was ordered (see the Figures). What do these images reveal?

DISCUSSION

Figure 1 demonstrates a mass in the sigmoid colon. Figure 2 provides a closer look at the mass, showing a large polyp on a stalk (a pedunculated polyp).

Several types of polyps can occur in the colon, including adenomatous, hyperplastic, and inflammatory types. Most adenocarcinoma of the colon arises from adenomatous polyps; hyperplastic or inflammatory polyps do not usually become precancerous. Histologically, adenomatous polyps can be divided into tubular, tubulovillous, and villous adenomas. Villous adenomas may be sessile or pedunculated and are considered to have the greatest malignant potential. For any polyp less than 5 mm in size, the incidence of cancer is 0.01%. In a 5- to 10-mm polyp, the cancer risk is approximately 1%; in a 10- to 20-mm polyp, it is approximately 10%; and in a polyp larger than 2 cm, the risk jumps to 30% to 50%.

COLORECTAL CANCER is the third most common cancer in the United States and one of the leading causes of cancer deaths, but it has a high 5-year survival rate (approximately 90%) if diagnosed early.

Symptoms of colon cancer do not tend to manifest until late in the disease. They may include anemia, a change in bowel habits lasting more than a few days, rectal bleeding or blood in the stool, abdominal pain or cramping, weakness, fatigue, bowel obstruction, or unexplained weight loss.

Risk factors include age older than 40 years, a diet high in fat and cholesterol, inflammatory bowel disease (IBD), alcohol or tobacco use, a personal history of colorectal cancer or polyps, a positive family history, obesity, diabetes, Eastern European Jewish ancestry, or a genetic predisposition due to familial adenomatous polyposis (FAP) or hereditary nonpolyposis colorectal cancer (HNPCC). Irritable bowel syndrome does not increase the risk of colon cancer.

Most patients with colorectal cancer do not have a family history of the disease, but the risk is increased when a first-degree relative received a diagnosis of colorectal cancer or polyps before age 60 years or when two or more first-degree relatives received such a diagnosis at any age. Screening for this group of people should begin earlier and occur more frequently than in the average population.

For those with a family history of FAP, screening should begin in the teens, and the colon should be removed surgically when patients are in their 20s. In FAP, a mutation of the APC tumor suppression gene causes hundreds of polyps to develop in the colon. The chance that colon cancer will develop in one or more of the polyps is 100%.

For patients with a family history of HNPCC, screening should start in their 20s. Patients with this family history usually develop only a few polyps, but the lifetime risk of developing colorectal cancer is 80%. HNPCC is also associated with cancers of the ovaries, small bowel, pancreas, stomach, kidneys, ureters, and bile ducts.

The American Cancer Society (ACS) recommends that people with IBD undergo screening colonoscopy 8 to 12 years after IBD is diagnosed and that the test be repeated every 1 to 2 years thereafter.

For average-risk patients (those without a family or personal history of any of the aforementioned conditions), screening should begin at age 50 years. The ACS recommends (1) fecal occult blood testing (FOBT) or fecal immunochemical test (FIT) every year; (2) flexible sigmoidoscopy every 5 years; (3) FOBT or FIT every year plus flexible sigmoidoscopy every 5 years; (4) barium enema every 5 years; or (5) colonoscopy every 10 years.

Flexible sigmoidoscopy visualizes only the distal colon, and up to 50% of polyps develop proximal to the area seen by the sigmoidoscope. A negative result on FIT or FOBT does not exclude colon cancer or polyps. These tests only detect blood in the colon; they are not specific enough to determine where the blood is coming from, nor can they alert you to the possibility of a polyp or cancer that is not bleeding. Colonoscopy is recommended if the FOBT or FIT result is positive, if barium enema demonstrates an abnormality, or if a polyp is detected with flexible sigmoidoscopy.

RADIOLOGY plays an important role in colon cancer diagnosis and polyp detection. Barium enema is frequently used as a screening test to evaluate the colon, whether or not the patient is symptomatic. It may also be done if colonoscopy was attempted but not completed. Colonoscopy is considered the gold standard, but it does carry risks, including those associated with sedation and the possibility of perforation, and is expensive. Air contrast—also called double contrast—barium enema can visualize the entire colon without the need for sedation. It carries less risk of perforation and costs less than colonoscopy. However, it is less sensitive than colonoscopy for detecting polyps that are less than 1 cm in size. And if a polyp is detected, the patient will still need colonoscopy to biopsy the lesion.

Colon cleansing and preparation are required before both colonoscopy and barium enema. If the colon is not adequately prepared, the tests are much less sensitive and a small polyp could easily be missed.

Air contrast barium enema is more sensitive than single contrast barium enema but is not suitable for everyone. In an air contrast study, an enema tip is placed in the rectum and a small amount of thick barium is introduced. Air is then pumped into the colon. The idea is to coat the lining of the colon to enhance the detail of the mucosa. This test requires that the patient be able to roll around on the fluoroscopy table and possibly to stand, so people with limited mobility or comprehension may not tolerate it. People with diverticular disease may also require a single contrast test, as the numerous diverticula can be distracting or confusing in an air contrast study and can increase the possibility of missing a small polyp. Single contrast barium enema is also used when colonic obstruction is suspected. A third type of enema uses a water-soluble contrast agent to fill the colon. This is mainly reserved for cases of suspected perforation, as the water-soluble contrast is absorbable by the body and is less likely to cause peritonitis if it extravasates into the peritoneum.

In virtual colonoscopy, a noninvasive test, the colon is filled with air from the rectum and CT of the colon is performed. The images are reconstructed to mimic the appearance of a true colonoscopy. The usefulness of this test is still under investigation and, according to the ACS, it is not recommended as a replacement for any of the current screening tests.