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 similar
to, 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
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. 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. 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 most
frequently affected by diseases such as colorectal cancer, for example the
rectum. For the procedure, the patient must lie
on his or her left side on the examining table. The physician inserts a short,
flexible, lit tube into the rectum and slowly guides it into the colon. The
tube is called a sigmoidoscope. The scope transmits an image of the inside
of the rectum and colon, so the physician can carefully examine the
lining of these organs. The scope also blows air into these organs, which
inflates them and helps the physician see better.
If anything unusual is in the rectum or colon, like a polyp or inflamed tissue,
the physician can remove a piece of it using instruments inserted into the
scope. The physician will send that piece of tissue to the lab for testing.
Bleeding and puncture of the colon are possible complications of sigmoidoscopy.
However, such complications are uncommon.
Flexible sigmoidoscopy takes 10 to 20 minutes. During the procedure, the
patient might feel pressure and slight cramping in the lower abdomen, but he or
she will feel better afterward when the air leaves the colon.
Preparation The colon and rectum must be completely
empty for flexible sigmoidoscopy to be thorough and safe, thus the patient must
drink only clear liquids for 12 to 24 hours beforehand. This includes 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 an enema, 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.
Rigid sigmoidoscopy Rigid sigmoidoscopy may be useful in
ano-rectal diseases such as bleeding per rectum or inflammatory rectal disease,
particularly in the general practice and pediatrics.
For performing the examination, the patient must lie on the left side, in
the so-called Sims' position. The bowels are previously emptied with a
suppository, and a digital rectal examination is first performed. The
sigmoidoscope is lubricated and inserted with obturator in general direction of
the navel. The direction is then changed and the obturator is removed so that the
physician may penetrate further with direct vision. A bellows is used to
insufflate air to distend the rectum. Lateral movements of the sigmoidoscope's
tip negotiate the Houston valve and the recto-sigmoid junction.
Benefits Several studies have shown the potential
benefits of sigmoidoscopy in detecting colorectal cancer.
In a 2009 Norwegian study, results were somewhat inconclusive at seven years.
“We found a trend towards reduced mortality from colorectal cancer for
both total colorectal cancer mortality and rectosigmoidal cancer mortality, but
this was not statistically significant in intention to screen analysis.
Corresponding reductions in mortality among attenders were 59% and 76%, both
statistically significant compared with the control group”.
The study saw no detectable difference in all-cause mortality.
A 2010 British study showed sigmoidoscopy reduced "overall
colorectal cancer incidence and mortality by 31 percent," and “incidence
of cancer in just the lower part of the colon was reduced by approximately 50
percent for those who underwent screening compared with those in the
control group.” Overall colon-cancer mortality was reduced by 43%. The study
also showed that the effect was persistent—a single sigmoidoscopy
reduced cancer rates for the length of the 11 year study.
Risks Although generally considered quite
safe, sigmoidoscopy does carry the very rare possibility of tearing of the
intestinal wall by the instrument, which could require immediate surgery to
repair the tear; in addition, removal of a polyp may sometimes lead to localized
bleeding which is resistant to cauterization by the instrument and must
be stopped by surgical intervention. See also
Colonoscopy Notes
References Flexible Sigmoidoscopy. National
Digestive Diseases Information Clearinghouse. National Institute for
Digestive and Kidney Diseases. Public domain text used as source for this
article. Rigid Sigmoidoscopy. The Wales Day
Centre. External links
Sigmoidoscopy Patient Experiences Flexible Sigmoidoscopy - NIH