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. Sigmoidoscopy is an examination used to look inside the lower part of the bowel. The examination itself doesn't hurt, but it can be followed by discomfort similar to that which follows intestinal colic. This is because it's necessary for the doctor to blow a small amount of air into the intestine in order to see inside it clearly.
On the day of the examination an enema or suppository is used to soften the stools that need to be evacuated from the lower part of the intestine. The patient needs to lie down, usually on their side with their knees brought up to their elbows. This makes it relatively easy for the doctor to perform the examination through the rectum.
After the doctor has examined the rectum by inserting a finger (digital rectal examination), the sigmoidoscope is inserted. Air is blown through the tube, which is also fitted with a light source and a very small camera. The sigmoidoscope is pushed very slowly 18 to 22cm inside the intestine, then gently pulled back out while the doctor carefully studies the lining for any abnormalities such as inflammation or tumours. Biopsy samples of suspicious-looking tissue can also be taken and studied later under a microscope.
Since it's difficult to study the lowest part of the intestine (rectum) with the lengthy sigmoidoscope a proctoscope is used instead.
This is only 7 to 10cm long, and can be inserted immediately after the sigmoidoscope is removed, allowing the doctor to study the rectum.
The examination can be performed without anaesthetic as an outpatient investigation and rarely lasts more than 10 to 15 minutes. After the examination the patient can go home right away. Sometimes a light sedative is given to help the patient relax during the procedure. 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 an 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.
Physicians may use the procedure to find the cause of diarrhoea, 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 most frequently affected by diseases such as colorectal cancer, for example the rectum.
Bleeding and puncture of the colon are possible complications of sigmoidoscopy. However, such complications are uncommon. 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. 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 no longer has the value it had in the past, before the advent of videocolonoscopy (flexible sigmoidoscopy). However, it may be still useful in ano-rectal diseases such as bleeding per rectum or inflammatory rectal disease, particularly in the general practice and paediatrics.
For performing the examination, the patient must lie on the left side, in the so called Sim's 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 obturaror 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.
Although generally considered quite safe, sigmoidoscopy does carry the very rare possibility of tearing of the intestinal wall by the instrument, which would require immediate major 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.
Edited by: John Sandham IEng MIET MIHEEM