Sigmoidoscopy - examining the rectum

Reviewed by Dr John Pillinger, GP

What is sigmoidoscopy?

Sigmoidoscopy is an examination used to look inside the lower part of the bowel. The examination itself doesn't hurt, but can be followed by discomfort similar to that which follows intestinal colic. This is because it is necessary for the doctor to blow a small amount of air into the intestine in order to see inside it clearly.

What happens before the examination?

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.

What happens during the examination?

After the doctor has examined the rectum by inserting a finger (digital rectal examination), the sigmoidoscope (a metal or plastic tube) 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 is 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.

Is it necessary to stay in hospital?

The examination can be performed without anaesthetic as an outpatient treatment 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, and if so then they will need to be driven home by someone else.

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