IBS Fact : Evidence-based management of irritable bowel syndrome

Diagnostic testing for IBS

As discussed in the previous article, IBS does not cause any specific physical alterations that can be verified by a physician on examination. Diagnosis of IBS is therefore primarily based on symptoms such as abdominal pain and abnormal bowel movements. Nonetheless, additional examinations are sometimes recommended to exclude other possible causes of IBS that produce similar symptoms. This is particularly true for elderly patients and those with certain symptoms, the so called red flags. Additional examinations may also be required if a dedicated IBS treatment is not followed by any significant improvement of the symptoms, as this may indicate the presence of another pathology. Finally, patients themselves may want to undergo an extended examination to remove any doubts and worries. Here, colonoscopy and sigmoidoscopy are the most common and comprehensive procedures to exclude several other diseases that produce symptoms similar to IBS.


Flexible sigmoidoscopy

Flexible sigmoidoscopy is a visual inspection of the rectum and the lower part of the colon (also known as the sigmoid colon, hence sigmoidoscopy). This is performed using an endoscope, which consists of a thin flexible tube with a camera and a light source mounted on its top. Using the endoscope, the doctor can inspect the lining of the colon for inflammation, ulcers, abnormal growth such as tumours and polyps, and bleeding. It also allows collection of small tissue samples (biopsies) from any suspicious area. These can be further analysed by microscopy to determine more precisely the type of inflammation or to exclude any possible malignancy. Polyps (cherry-like protuberances), which are usually harmless, can also be removed if found. Since IBS is not accompanied by any visible changes of the intestinal wall, sigmoidoscopy is primarily performed to exclude other diseases, particularly in patients with certain red flags such as abdominal pain, rectal bleeding, constipation, unexplained weight loss, or black, tarry stools. Patients above 50 and those with a familial history of intestinal cancers may also be recommended to undergo a sigmoidoscopy to check for colon and rectal cancer. Sigmoidoscopy may be indicated in persons with a familial history of IBD, such as Crohns disease and ulcerative colitis.

What is the preparation for flexible sigmoidoscopy?

To enable visibility, the colon has to be cleaned out prior to the procedure. This is usually done by enema right before the examination. You may also be required to drink only clear liquids for 12 to 24 hours beforehand and refrain from ingesting any food eight hours before the procedure. Although laxatives are usually not required, they may be prescribed in some hospitals or clinics. These are usually taken the night before the procedure and require frequent bathroom visits, which is considered by many patients more cumbersome than the actual procedure. You may also be requested to refrain from taking certain medications prior to the exam. Sedation is usually not required for this test, but it may be an option to discuss with your doctor ahead of time. If you choose to have a sedative, you will need to make sure that someone accompanies you home. You should also not drive a car for the rest of the day.

What will I experience during flexible sigmoidoscopy?

Sigmoidoscopy is usually performed at the hospital or clinic in a dedicated room. Your doctor will have you lie on your left side, with your knees drawn up. He will insert the sigmoidoscope through the rectum and pass it into your sigmoid colon. The doctor will use a small amount of air to expand the colon for better visibility. You will be encouraged to pass wind to prevent cramping. The doctor will carefully retract the sigmoidoscope while examining the lining of your bowel on a display. You may feel mild cramping during the procedure. The exam takes 10 to 20 minutes. The collection of tissue samples or removal of polyps may be experienced as slightly painful.

What can I expect after a sigmoidoscopy?

Once you have had your test, you will be monitored in a recovery area until well enough to get up. Usually you can resume regular activities right away after the procedure. If you have had sedation, you may feel sleepy for up to 24 hours. Ask your doctor if you’ll need to miss work for a sigmoidoscopy. You will also be given information about follow-up care and what to do if you have a problem. After a sigmoidoscopy, you can expect some abdominal cramping or bloating during the first hour after the procedure. Mild anal bleeding is common and normal, particularly if polyps were removed. Although complications are rare, you should call you doctor immediately if you experience severe abdominal pain, fever or heavy rectal bleeding.

How are the results of a sigmoidoscopy interpreted?

Results of a sigmoidoscopy are generally available right after the procedure. Biopsy results may take a few days. For the majority of patients with suspected IBS, sigmoidoscopy will yield normal (negative) results, i.e. normal appearance of the intestinal mucosa. This further strengthens the diagnosis of IBS and excludes the majority of conditions with similar symptoms with high accuracy. In case of abnormal findings, further examinations, such as colonoscopy (see below) may be indicated.


Like sigmoidoscopy, colonoscopy consists of a visual assessment of the bowels using an endoscope, In colonoscopy, however, the endoscope is advanced deeper into the colon to examine its entire length. This allows for a more thorough examination, but is more invasive. Accordingly, colonoscopy is often indicated as a second step once sigmoidoscopy produces suspicious findings. Colonoscopy allows screening of the colonic mucosa for signs of pathology, such as inflammation, bleeding, tumours, constrictions, scarring, polyps or other abnormalities. It also allows the collection so small tissue samples (biopsy) from any suspicious areas for microscopic analysis. If necessary, small surgical procedures such as removal op polyps or closure of bleeding ulcers can also be carried out by endoscopy. The examination is indicated in patients over the age of 50 years and those with a family history of colorectal cancer or presence of alarm symptoms such as unexplained weight loss or anaemia, or bleeding from the gastrointestinal tract.

What is the preparation for colonoscopy?

Colonoscopy requires a more thorough cleansing of the bowel than sigmoidoscopy. This is achieved by a special diet for a few days before the test, and an enema shortly before the test. In addition, laxatives and large amount of liquid must be taken the day or evening before. Because of the resulting intense diarrhoea, the laxative preparation is considered by many as the most unpleasant part of the procedure. It also requires the patient to stay close to a bathroom. Colonoscopies are usually performed under moderate, so called conscious sedation, or under general anaesthesia. With conscious sedation the patient is drowsy and experiences little or no discomfort, but remains conscious and is able to understand and respond to verbal commands. In contrast, patients receiving general anaesthesia remain completely unconscious during the procedure. Moderate sedation is most commonly used for colonoscopies and is sufficient for a pain-free examination, although this may vary from patient to patient. Full anaesthesia is usually recommended for patients considered at high risk because of age, illness, or a prior history of complications with drugs used for conscious sedation. Some clinics work exclusively with full anaesthesia while other leave the choice to the patient. Do not hesitate to ask questions and clarify any doubts with regard to the anaesthesia prior to the procedure. This will help to reduce anxiety and make the procedure less unpleasant. Remember that you cannot drive after sedation, so ask a family member or friend to pick you up afterwards or book a taxi. You will also need somebody to accompany you home as you will be drowsy with the sedative. Prior to the procedure, you should also talk with your doctor about any medical conditions you have and all prescribed and over-the-counter medicines, vitamins, and supplements you take, including:

Your doctor may need to adjust to these medications before the procedure. The preparation is very important step for a successful colonoscopy. It improves accuracy and visibility, and shortens the procedure since debris do not need to be cleaned out. You should therefore follow all instructions and ask questions in case of doubt and report any abnormalities you observe.

How is colonoscopy performed?

When you arrive for your colonoscopy, you will change into a hospital gown that opens at the back. You will then be bought to a private room and lie on your left side on an examination table. You will be given the the anaesthesia through an intravenous line. It has a fast onset of action, meaning you will feel the effects within 1-2 minutes. The doctor will then first examine your anus with a finger and then gently insert the colonoscope, which is about the thickness of a finger. Although your doctor will use lubricating jelly, this might feel uncomfortable. The colonoscope has a light and video camera mounted on its tip so the doctor can see the lining of your colon on a monitor. Your doctor will pump a small amount of air into your bowel to inflate it slightly for a better view. You will be encouraged to pass wind to prevent cramping. The flexible colonoscope will then be advanced slowly through your bowel. Your doctor might ask you to change your position and press slightly on your abdomen to help move the colonoscope in the right direction. Once the tip of the colon or the last portion of the small intestine is reached, the colonoscope is slowly withdrawn while the lining of your bowel is carefully examined. Small tissue samples (biopsy) may be collected and polyps removed. This may be slightly painful. Polyps are usually benign, but in rare cases may change into cancer over time. The removed polyps are therefore sent to a laboratory to verify their benign character. Tissue samples, usually from suspicious areas, are also sent to a laboratory for detailed analysis by microscopy and laboratory testing. This provides additional information on any possible abnormality. Once the lining of the entire colon has been inspected, which takes about 30 minutes, the colonoscope will be carefully removed and you will be brought to a recovery room.

What can I expect after a colonoscopy?

Once the colonoscopy has been completed, you will be monitored for 1 to 2 hours. You may feel a bit tired or sleepy from the sedative. Abdominal cramping or bloating is normal during the first hour after the procedure. You may also pass a small amount of blood from your anus if a biopsy was removed. After the effects of the sedative have passed, you should be ready to go home, but you should be accompanied by a friend or family member. Your doctor will also give you additional instructions on the aftercare. Because of the laxatives used for the cleansing, you may still lose some liquid from your anus and pass gas for up to 24 hours after taking the last dose. The day after the colonoscopy, you should stay on easy-to-digest foods to give your intestines a rest. You should be fully recovered by the next day and be able to go back to a normal diet.

What are the possible side effects of colonoscopy?

Colonoscopy is a relatively save routine diagnostic procedure and complications are rare. However, as with each invasive examination, adverse reactions or complicaitons may occur in a small number of cases. This may be an intollerance to the sedative or pain madication given prior tot he procedure resulting in heart or breathing problems. Since patients are closely monitored during the procedure, any adverse response to such drugs will be noticed and treated imediately by the attendig staff. Other, more delayed, side effects are prolonged bleeding from the site where a tissue sample (biopsy) was collected or a polyp was removed. In very rare cases, the introduction of the colonoscope injure the intestinal wall of the colon, causing perforation, bleeding or infection. The physician performing your colonoscopy will give you a list of symptoms that may indicate such complications along with instructions on what to do if you experience them. In general, yoiu should conctact a doctor imediately in case of:

How are the results of a colonoscopy interpreted?

Because colonoscopy is a visual examination, the main results are available right after the procedure. The doctor or nurse may discuss them briefly after the sedatives or anaesthesia has worn off. In addition, you may receive an invitation for a more thorough discussion of the results at a later time. This is especially the case if polyps or tissue samples have been removed and are examined in the laboratory, which may take days to weeks. As IBS is not associated with structural changes of the intestinal wall, the results of colonoscopy are negative in patients with true IBS. In contrast, if any changes of the colonic mucosa, such as inflammation, are observed, it may indicate another condition and require additional testing and specific treatment.

 Diagnostic testing for IBS: Part II

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