Sigmoidoscopy Health Article

Definition

Sigmoidoscopy is a diagnostic and screening procedure in which a rigid or flexible tube with a camera on the end (a sigmoidoscope) is inserted into the anus to examine the rectum and lower colon (bowel) for bowel disease, cancer, precancerous conditions, or causes of bleeding and pain.

Purpose

Sigmoidoscopy is used most often in screening for colorectal cancer or to determine the cause of rectal bleeding. It is also used in diagnosis of inflammatory bowel disease, microscopic and ulcerative colitis, and Crohn's disease.

Cancer of the rectum and colon is the second most common cancer in the United States. About 155,000 cases are diagnosed annually. About 55,000–60,000 Americans die each year of colorectal cancer.

A number of studies have suggested, and it is now recommended by cancer authorities that people over 50 be screened for colorectal cancer using endoscopy every three to five years. Individuals with inflammatory bowel disease, such as Crohn's disease or ulcerative colitis, who are at increased risk for colorectal cancer, may begin their screenings at a younger age, depending on when their disease was diagnosed. Many physicians screen such patients more often than every three to five years. Screening should also be done in patients who have a family history of colon or rectal cancer or small growths in the colon (polyps).

Some physicians do this screening with a colono-scope, which allows them to see the entire colon. However, most physicians prefer sigmoidoscopy, which is less time consuming, less uncomfortable, and less costly.

Studies have shown that one quarter to one-third of all precancerous or small cancerous growths can be seen with a sigmoidoscope. About one-half are found with a 1 ft (30 cm) scope, and two-thirds to three-quarters can be seen using a 2 ft (60 cm) scope.

In some cases, the sigmoidoscope can be used therapeutically in conjunction with other equipment, such as electrosurgical devices, to remove polyps and other lesions found during the sigmoidoscopy.

Precautions

Sigmoidoscopy can usually be conducted in a physician's office or an outpatient clinic. However, some individuals should have the procedure done in a hospital day-surgery facility. Those with rectal bleeding may need full colonoscopy in a hospital setting. Patients whose blood does not clot well (possibly as a result of blood thinning medications) may need the procedure performed in a hospital setting as well.

Individuals with renal insufficiency or congestive heart failure need to be prepared in an alternative way, and must be carefully monitored during the procedure.

Sigmoidoscopy may be contraindicated in patients with severe active colitis or toxic megacolon (an extremely dilated colon). In general, patients on continuous ambulatory peritoneal dialysis are not candidates due to a high risk of developing intraperitoneal bleeding.

Description

Sigmoidoscopy may be performed using either a rigid or flexible sigmoidoscope, a thin tube with fiberoptics, electronics, a light source, and camera. The physician inserts the sigmoidoscope into the anus to examine the rectum (the first 1 ft/30 cm of the colon) and its interior walls. If a 2 ft/60 cm scope is used, the next portion of the colon can also be examined for any irregularities. The sigmoidoscope's camera is connected to a viewing monitor (television screen), so the rectum and colon are enlarged and viewed on a monitor. Images can then be recorded as still pictures for hard copy or the entire procedure can be videotaped.

If polyps, lesions, or other suspicious areas are found, the physician biopsies them for analysis. During the sigmoidoscopy, the physician may also use forceps,

KEY TERMS

Biopsy—The removal a small portion of tissue during sigmoidoscopy to perform laboratory tests to determine if the tissue is cancerous.

Colonoscopy—A diagnostic endoscopic procedure that uses a long flexible tube called a colonoscope to examine the inner lining of the entire colon; used for colorectal cancer screening and more thorough examination of the colon.

Colorectal cancer—Cancer of the large intestine, or colon, including the rectum (the last 16 in of the large intestine before the anus).

Congestive heart failure—Excess fluid accumulation in the lungs and surrounding tissues due to the weakness of the heart muscle and the inability to pump sufficiently.

Electrosurgical device—A medical device that uses electrical current to cauterize or coagulate tissue during surgical procedures, often used in conjunction with laparoscopy.

Inflammatory bowel disease—Ulcerative colitis or Crohn's disease; chronic conditions characterized by periods of diarrhea, bloating, abdominal cramps, and pain, sometimes accompanied by weight loss and malnutrition because of the inability to absorb nutrients.

Pathologist—A doctor who specializes in the diagnosis of disease by studying cells and tissues under a microscope.

Polyp—A small growth, usually not cancerous, but often precancerous when it appears in the colon.

Renal insufficiency—The inability of the kidneys to process fluid fast enough to flush the body of impurities.

graspers, snares, or electrosurgical devices to remove polyps, lesions, or tumors.

The sigmoidoscopy procedure takes five to 20 min utes. Preparation begins one day before the procedure. There is some discomfort when the scope is inserted and throughout the procedure, similar to that experienced when a physician performs a rectal exam using a finger to test for occult blood in the stool (another major colorectal cancer screening test). The patient may also feel some minor cramping pain. There is rarely severe pain, except for individuals with active inflammatory bowel disease.

Private insurance plans almost always cover the $150 to $200 cost of sigmoidoscopy for screening in healthy individuals over 50, or for diagnostic purposes. Medicare covers the cost for diagnostic exams, and may cover the costs for screening exams. Medicaid varies by state, but does not cover the procedure in most states. Some community health clinics offer the procedure at reduced cost, but this can only be done if a local gastroenterologist (a physician who specializes in treating stomach and intestinal disorders) is willing to donate his or her time.