A sigmoidoscopy is a procedure that allows doctors to look into the sigmoid area of the colon and rectum using a thin tube called a sigmoidoscope. There are two types of sigmoidoscope, which include a flexible sigmoidoscope and a rigid sigmoidoscope; the flexible sigmoidoscope is more commonly used because it allows doctors to see more of the colon. Sigmoidoscopes are fitted with a light source and tiny camera, which sends images of the body’s interior to an external monitor.
The sigmoid colon is the lower portion of the colon and attached to the rectum.
Why would I need a sigmoidoscopy?
A sigmoidoscopy allows doctors to see the lower part of the colon and rectum in detail. You may be advised to have a sigmoidoscopy if you have symptoms such as lower abdominal pain, changes in bowel habits or bleeding from the rectum (also known as the back passage). The test can detect abnormalities, blockages and symptoms of conditions, including:
A sigmoidoscopy can also be used to remove biopsy samples and polyps. A biopsy is a very small piece of tissue which is sent to a laboratory for analysis under a microscope.
As most cases of bowel and colorectal cancer develop in the lower portion of the colon and rectum, a sigmoidoscopy is carried out on a regular basis in patients who display symptoms of bowel cancer. These include blood in the faeces, changes in bowel habits, abdominal pain and unexplained loss of weight. There are plans to introduce a routine sigmoidoscopy test into the bowel cancer-screening programme to try and reduce the number of cases and ensure early diagnosis. This would involve people aged over 55 as bowel cancer is much more common in older people.
Preparing for a sigmoidoscopy
If you have been advised to have a sigmoidoscopy you will be sent a letter from the hospital explaining how you should prepare for your test, detailing when you need to arrive and which department you must go to. In most cases a sigmoidoscopy is carried out as day cases and you will not be required to stay over.
Your colon needs to be empty during the test to enable doctors to see clear images, so you will be asked to avoid eating or drinking for a period of time before the test and to take laxatives to ensure that your bowel is empty. If the bowel is not empty the images may not be clear and the test may need to be repeated. The most commonly used laxative is called Picolax. In some cases an enema is given before the test to clear the bottom of the colon.
Before the test you will be asked to take off your clothes and put on a hospital gown. A doctor or nurse will explain what is going to happen and answer any questions you may have. You will then be asked to lie on your left hand side with your knees pulled up to your chest.
What does the procedure involve?
The test is quick (usually between 15 and 20 minutes), simple and should not be painful; although it may feel uncomfortable. A doctor or nurse will insert their finger (they will be wearing gloves and the finger will be lubricated to reduce pain) into the anus to widen it and check for any blockages, before inserting the sigmoidoscope. The sigmoidoscope will then be pushed gently upwards through the rectum and into the sigmoid colon. Air will be pumped through to make the images clearer, which may make you bloated. The lining of the bowel is examined as the sigmoidoscope is gently pulled out. In some cases a biopsy sample will be taken during the test.
After the test
In most cases the patient is free to go home as soon as they feel ready. However, if they were sedated before the test, they may be advised to wait a while until the effects of the sedative have worn off fully. Before you leave your doctor or nurse may talk to you about what they saw on the images of your colon and rectum, but the test results may take a while to come back if you have had polyps removed or a biopsy taken. It is advisable to ask somebody to give you a lift home as you will probably not feel like driving. When you get home it is advisable to rest for the remainder of the day.
Are there any risks?
As with all medical procedures a sigmoidoscopy does carry risks, but the procedure is regarded as very safe and the benefits far outweigh the risks in most cases. Possible side-effects of a sigmoidoscopy include:
- Abdominal pain.
Possible complications of a sigmoidoscopy include:
- A tear in the bowel.
- Abnormal bleeding.
- Problems with your heart rate and blood pressure caused by sedatives. However, this is very rare as your blood pressure, heart rate and breathing will be monitored throughout the test.
You should see a doctor immediately if you experience the following symptoms within 48 hours of having a sigmoidoscopy:
- Bleeding from the rectum or blood in the faeces.
- Severe pain in the abdomen.