Sigmoidoscopy is the minimally invasive medical
examination of the large intestine from the rectum through the last part of the
colon. There are two types of sigmoidoscopy, flexible sigmoidoscopy, which uses
a flexible endoscope, and rigid sigmoidoscopy, which uses a rigid device.
Flexible sigmoidoscopy is generally the preferred procedure. A sigmoidoscopy is
a very effective screening tool. A sigmoidoscopy is similar but not the same as
a colonoscopy. A Sigmoidoscopy only examines up to the sigmoid, the most distal
part of the colon, while colonoscopy examines the whole large bowel.
Flexible sigmoidoscopy enables the physician to look at the
inside of the large intestine from the rectum through the last part of the
colon, called the sigmoid or descending colon. Physicians may use the procedure
to find the cause of diarrhea, abdominal pain, or constipation. They also use it
to look for benign and malignant polyps, as well as early signs of cancer in the
descending colon and rectum. With flexible sigmoidoscopy, the physician can see
intestinal bleeding, inflammation, abnormal growths, and ulcers in the
descending colon and rectum. Flexible sigmoidoscopy is not sufficient to detect
polyps or cancer in the ascending or transverse colon (two-thirds of the colon).
However, although in absolute terms only a relatively small section of the large
intestine can be examined using sigmoidoscopy, the sites which can be observed
represent areas which are affected by diseases such as colorectal cancer most
The colon and rectum must be completely empty for flexible sigmoidoscopy to be
thorough and safe, so the physician will probably tell the patient to drink only
clear liquids for 12 to 24 hours beforehand. A liquid diet means fat-free
bouillon or broth, gelatin, strained fruit juice, water, plain coffee, plain
tea, or diet soft drinks. The night before or right before the procedure, the
patient receives a laxative and a colonic, which is a liquid solution that
washes out the intestines.
No sedation is required during this procedure as long as the examination does
not exceed the level of the splenic flexure.