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Investigations into Crohn’s Disease

Investigations are necessary to reach the correct diagnosis and to check on the progress of the disease. After an initial examination in the clinic, some of the following tests may be required:


1. Blood tests

  1. to check for anaemia
  2. to check the number of white blood cells and platelets which may be raised in presence of inflammation and infection, or be affected by certain drugs, e.g. azathioprine
  3. to check if there is an imbalance of salts (e.g. sodium and potassium) and water due to diarrhoea or after steroid treatment
  4. to check the proteins in the blood
  5. a low level of albumin suggests severe ulceration. It can also cause the ankles to swell
  6. raised C-reactive protein reflects inflammation
  • to check the condition of the liver
  • to check if sufficient vitamins and minerals are being absorbed by the damaged gut - e.g. B12, D, folic acid, iron, calcium, magnesium, zinc.

    • 2. Stool Culture

    A relapse may sometimes be due to an infection of the gut caused by bacteria (eg Clostridium difficile), which can be detected in the stool.

    3. Abdominal X-ray

    This is a plain X-ray of the abdomen. It is a simple, quick and painless examination, which may be carried out to highlight:
    1. Right-sided (proximal) constipation in the presence of left-sided (distal) inflammatory disease.
    2. Swelling (dilatation) of the bowel due to stricture formation or severe inflammation (as in fulminant colitis or toxic megacolon).
    3. Complications such as perforation.

    The examination does not require any special preparation and can usually be performed on request from clinic. The results can be reviewed by your doctor and appropriate treatment given, or further investigation continued.

    4. Barium x-rays

    Barium sulphate is a liquid, which shows up on x-ray and can, therefore, be used to demonstrate the bowel, which would otherwise be poorly seen. It may be given by mouth to examine the small intestine or by enema to examine the large intestine. It may show areas of active disease, narrowing or the development of fistulae and tumours. Nowadays barium x-rays are increasingly replaced by MRI scanning, which does not expose the patient to repeated irradiation.

    5. Barium Enema

    Uses

    It is used in enema form for highlighting diseases of the large bowel, e.g. CD and ulcerative colitis (UC). Sometimes it may also flow back into the terminal ileum to reveal disease there.

    Preparation

    This involves cleaning all waste material from the bowel and following a special diet. Instructions must be followed carefully as poor preparation may spoil the results.
    The day before examination a strong laxative solution is given. This is usually two sachets of Picolax - one sachet is taken at 8am and the second is taken 2-4 hours after lunch. To reduce the formation of faeces a special diet is taken:

    Breakfast

    Boiled egg, White toast, Black tea or coffee

    Lunch

    White meat / White fish
    Boiled or mashed potatoes or rice, (No vegetables), (No fruit)
    Fruit flavoured jelly / Plain yoghurt / Black tea or coffee / Fruit squash

    Supper

    Clear soup
    Fruit flavoured jelly
    Black tea or coffee
    Fruit squash

    N.B. It is most important that liberal amounts of fluid are taken during the day as Picolax can cause the frequent passage of watery motions, leading to dehydration. A glass of water should be taken every hour.

    You will be asked to have nothing further to eat from midnight except your usual medication. You may continue to drink water only. If you have an afternoon appointment you can usually have the restricted breakfast as on the previous day.

    The Examination

    Barium, together with a little air to inflate the bowel, is administered through a tube inserted in the rectum. A small injection of a substance called buscopan is given to relax the bowel muscle. The barium is then allowed to drain and a small amount of air is blown into the bowel. This distends the gut and allows 'double contrast' film to be taken in which the lining of the gut, coated in barium, stands out clearly against the air inside the bowel.

    This enables the radiologist to see quite small lesions such as ulcers and polyps. In order to get better views during the examination, the radiologist will ask you to turn onto your back and side and he will tilt the x-ray table.
    The radiologist will send a report to your doctor who will then prescribe the appropriate treatment or carry out further investigations.

    After the Test

    You will be given a laxative solution to help the barium pass more easily out of the bowel. You will find that the bowel motions will be white, due to barium, for the next few days. Try and get rid of as much barium as quickly as possible, as it sometimes leads to constipation.

    6. Barium Meal and Follow Through

    In this examination the barium is swallowed and followed through to the small intestine. It is usually done to make the diagnosis, or to study the progress of CD in the small intestine.

    Preparation

    You will be asked to eat or drink nothing for 6 hours prior to the examination. Normal medications may be taken.

    The examination

    This is carried out in the X-ray department. A barium drink is given highlighting the stomach and small intestine and a series of X-rays is taken. The radiologist may ask you to roll on your side and he may tilt the X-ray table to get better views.
    Sometimes the barium is slow to pass through to the small intestine and you may be in the department for up to four hours.

    After the test

    The radiologist will send a report to your doctor. A laxative is given at the end of the test to help the barium to pass out of the bowel more easily. Your bowel motions may be white, due to the barium, for the next few days.
    You may now eat and drink normally.

    7. Bile salt retention tests.(SeHCAT)

    Bile salts are important in the digestion of fat in our diet, and so the body re-cycles them. They are secreted in the bile in response to the presence of fat in the stomach and duodenum. When fat digestion is complete in the lower small intestine they are normally re-absorbed and travel back in the blood to the liver, where they can be secreted once again in the bile. The daily loss of bile-salts from the body is quite small. Sometimes disease of the terminal ileum means that the gut can no-longer absorb bile-salts. If this happens they pass into the large bowel, where they may cause diarrhoea, before passing out in the stools. This is an important mechanism of diarrhoea in CD and to diagnose it a SeHCAT test is performed.

    The patient attends the Nuclear Medicine department and is given a tiny dose of bile-salts labelled with radio-active selenium. This is allowed to equilibrate in the body and then the patient is asked to lie in a whole-body counter. This is made of very thick steel (often an old gun-turret from a naval battleship or cruiser) and does not allow radioctivity to escape. The total radioactivity of the patient is then recorded over several minutes. The patient then goes home. A week later he returns and goes into the whole body counter again. The amount of radiation remaining is measured and from this it is possible to calculate whether bile salts are being lost too rapidly from the body.

    8. Bone Density

    This is an X-ray examination carried out to determine the density (thickness) of bones in the body, usually the hip and spine. The amount of radiation used in the procedure is minute, but the examination must be avoided during pregnancy.

    Uses

    It is performed to detect the presence of osteoporosis, a condition in which the bones lack protein and become thin, weak and brittle, therefore increasing the risk of fractures or distortion, (e.g. kyphosis - bending of the spine). It can detect early changes so that preventative measures may be taken. The risk of developing osteoporosis is much increased after the use of corticosteroids such as prednisolone for the treatment of IBD.

    Preparation

    All metal objects must be removed from the area to be scanned as they may deflect X-rays.

    The Examination

    You will be asked to lie on your back on the X-ray couch. If it is a spinal X-ray, your legs will be raised on a cushion. The arm of the X-ray machine is then passed over the area several times and pictures are taken. You must remain still during the procedure but you can talk freely.

    After the Test

    The scans are reviewed and a report will be sent to your doctor.

    9. Faecal Calprotectin

    Calprotectin is a protein found in white blood cells in large quantities. It is surprisingly stable and a sample can be left at room temperature for several days before the calprotectin starts to break down. In active IBD white cells are drawn into the bowel by the inflammatory process directed against the gut bacteria. The cells breakdown releasing calprotectin which can then be measured in specimens of faeces. Increased amounts in the stool indicate not only the presence of inflammation, but also reflect its severity. The test is very simple - it is merely necessary to collect a small sample of faeces in a universal container and send it by post to the laboratory. Calprotectin is currently the most sensitive test available for determining the degree of inflammation present in the gut.

    10. Capsule endoscopy

    It is difficult to pass an endoscope (an enteroscope) down the small intestine, and x-rays and even MRI scans may not provide sufficient detail of changes in the lining of the bowel. Small lesions causing bleeding may be difficult to find. Capsule endoscopy is a relatively new way of examining the small bowel. It involves swallowing a small capsule, no bigger than a drug capsule, which contains a small camera which takes a series of pictures as it passes down the bowel. These pictures can be recorded, and later examined to see if there is any small intestinal disease. It may succeed in picking up quite small Crohn's ulcers, and thus help detect early disease. However its use in CD is limited because if there is any narrowing in the intestine the capsule might stick and cause an obstruction.

    11. Colonoscopy

    This is a visual inspection of the lining of the large bowel through a flexible fibre optic telescope called a colonoscope. Samples of tissue (biopsies) may be taken and examined under the microscope.

    Preparation

    A strong laxative solution will be given the day before the examination in order to clear the bowel so that good views of the tissue may be obtained. Instructions on how to take this and any dietary restrictions that need to be followed will be given.
    It is very important that instructions are followed carefully as a poor bowel preparation may lead to the test being abandoned so that it has to be repeated

    About the test

    On arrival in the department you will be asked to put on a hospital gown and sign a form giving consent to the procedure.

    The examination will take place on a couch and the nurse will help you into the correct position and stay with you throughout the procedure.

    The doctor will give you some sedation through a small needle in the back of the hand and once you become sleepy and relaxed, he will pass the instrument through the anus and along the bowel.

    The procedure should not be painful but you may feel a little uncomfortable as air is introduced to inflate the bowel so that good views can be obtained. This may make you feel like you need to have a bowel movement but this is unlikely as the bowel has been cleared.

    The examination can take as little as twenty minutes, but may be longer if there is spasm in the bowel. Your position may need to be changed to help the 'scope advance and the nurse will assist you if this is necessary.

    Once the examination is finished, the 'scope is removed and you will be left to slowly recover.

    After the test

    You may feel a little bloated with wind pains, but these usually settle quickly.

    The doctor will be able to speak to you once you are awake but if biopsies have been taken it will take a few days before a full report is available.

    Are there any side effects?

    The sedative may remain in the blood steam for several hours so you should take the remainder of the day quietly. Normal activities may resume the following day.

    It is also advisable that:
    1. You should not drive for twenty-four hours and you will need an escort home. (Your motor insurance would be invalid if you had an accident).
    2. You should not operate any dangerous machinery.
    3. You should not make any important decisions, (i.e. business transactions, make a Will, etc.).
    4. You should not drink alcohol for twenty-four hours.

    Are there any problems following colonoscopy?

    There is a very small risk of damage to the bowel wall following colonoscopy resulting in bleeding or perforation. (2 in 1,000 examinations, i.e. 998 are perfectly uneventful).

    If bleeding occurs this can be easily cauterised, (the passage of a small electric current to the bleeding point) but if a perforation occurs, it will usually require an operation to repair it.

    A small amount of bleeding may occur following the procedure, either due to local trauma or from a biopsy site. However, if this continues for more than a few days, or if the motions become black, you should inform your doctor straight away.

    12. Sigmoidoscopy

    This is an examination of the lower part of the bowel with an instrument called a sigmoidoscope. It may be rigid or flexible (the latter is performed in the Endoscopy Department of the hospital or in some centres this may be performed in the clinic).

    Rigid     sigmoidoscopy is usually performed in the Out-Patient Department of the hospital. It is not usually painful, but may be a little uncomfortable.

    You will be asked to lie on your left side, with your back positioned horizontally across the couch, bottom towards the edge, and knees slightly bent.

    After the doctor has examined the rectum with his finger, the lubricated tube is slid inside the anus, a little air is pumped in to inflate the bowel and the tube is advanced up to the sigmoid part of the colon. The doctor can inspect the tissue as the instrument has a light on the end, and take samples to send to the laboratory for examination under the microscope.

    You may have a feeling of wanting to have a bowel movement during the procedure but this is only due to pressure from the air and the presence of the tube in the bowel.

    At the end of the procedure, the nurse will give you some tissues to wipe away the excess jelly before you dress.

    Sometimes a little bleeding occurs following a biopsy and for the next 24 hours you may notice blood in the motions.

    If heavier bleeding occurs or if you pass clots from the back passage, you should see your own doctor as soon as possible for further advice.

    The advantage of using a flexible scope is that it allows inspection up to the splenic flexure (the top of the left-hand side of the colon). Samples of tissue (biopsies) may be taken and examined under the microscope.

    Preparation

    You will be asked to administer a small enema about three hours prior to arriving at the Endoscopy Suite (or clinic) so that the lower bowel is clear and good views can be achieved.

    About the test

    On arrival in the department you will be asked to put on a hospital gown and sign a consent form for the procedure.

    The examination will take place on a couch and the nurse will help you into the correct position and stay with you throughout the procedure.

    The doctor may give you some light sedation through a small needle into the back of your hand and once you become sleepy and relaxed, he will pass the instrument through the anus and along the bowel.

    The examination should not be painful but you may feel a little uncomfortable as air is introduced through the 'scope in order to inflate the bowel to give better views. This may make you feel like you need to have a bowel motion but is only due to pressure of the air and presence of the 'scope.

    The whole procedure usually takes around fifteen minutes; the 'scope is then removed.

    After the test

    You will be left to rest in the unit for at least fifteen minutes and may feel a little bloated with wind pains, but these usually settle quickly.

    The doctor will speak to you as soon as you are awake, but if biopsies are taken it may take a few days before the full report is available.

    Are there any after effects?

    The sedative may remain in the blood steam for several hours so you should take the remainder of the day quietly. Normal activities may resume the following day.

    It is also advisable that:
    1. You should not drive for twenty-four hours and you will need an escort home. (Your motor insurance would be invalid if you had an accident).
    2. You should not operate any dangerous machinery.
    3. You should not make any important decisions, (i.e. business transactions, make a Will, etc.).
    4. You should not drink alcohol for twenty-four hours.

    Potential problems following flexible sigmoidoscopy

    There is a very small risk of damage to the bowel wall following flexible sigmoidoscopy resulting in bleeding or perforation. (1 in 1,000 examinations, i.e. 999 are perfectly uneventful).

    If bleeding occurs this can easily be cauterised, (the passage of a small electric current to the bleeding point) or, if a perforation occurs, it will require a small operation to repair it.

    A small amount of bleeding may occur following the procedure either due to local trauma or from a biopsy site. However, if this continues for more than a few days, or if the motions become black, you should inform you doctor straight away.

    13. Hydrogen Breath Test

    Hydrogen is a gas that is present in the atmosphere in minute amounts. It cannot be produced by mammalian cells, so that all hydrogen excreted on the breath must be produced by bacteria living in the body.
    It is produced in the caecum (first part of the large bowel) when carbohydrates are fermented by the colonic bacteria. This is then absorbed into the bloodstream, taken to the lungs and is excreted on the breath.

    Uses

    As hydrogen is not usually present in quantities of more than 20ppm the test is useful in determining:
    1. Malabsorption of certain sugars, e.g. lactose (alactasia).
    2. Bacterial overgrowth in the small intestine (due to inflammation and strictures as seen in CD.

    Preparation

    1. Nothing to eat or drink after midnight prior to the test.
    2. No smoking from 6pm the night before. (Gases produced by the cigarette smoke may interfere with the measurement).

    About the Test

    It is a simple, painless test, which takes around 3½ hours. Breath samples are taken using a syringe and mouthpiece. This is placed in the mouth and on breathing out, the plunger is drawn back and the sample is retained in the syringe.

    A sample is taken on arrival in the department as a baseline, (i.e. fasting).

    This is followed by drinking a sugar solution (depending on what the doctor is looking for).

    Samples of breath are taken at half-hourly intervals and placed into a monitor and the amount of hydrogen in the sample is measured.

    At the end of the test, results are shown on a graph and analysed by computer.

    What happens next?

    The doctor will review the results and decide whether a special diet is indicated in order to exclude certain foods which may be causing your symptoms. It may be that foods are not considered to be accounting for the symptoms and further investigations might need to be carried out

    14. Intestinal Permeability Test

    What is it?

    This is a simple, painless test to see how well the small intestine is working.

    It may be carried out to assess damage to the lining of the small intestine due to inflammation in CD.

    Preparation

    Alcohol should not be taken for 48 hours prior to the test as this may lead to inaccurate results.

    Medications such as aspirin and other non-steroidal anti-inflammatory drugs (Voltarol, Ibuprofen etc.) should also be avoided for 24 hours before the test.

    No solid food should be eaten from midnight prior to the test.

    At least 2-3 cups of clear fluids (water, fruit squash, black tea or coffee) should be taken on the morning of the test. This is to ensure that a good amount of urine will be passed.

    How is it performed?

    On arrival at the department the test will be explained to you and you will be given a sweet test solution to drink. This contains 2 substances labelled with a small amount of radioactivity - 51Cr EDTA and 14C mannitol are often used but other sugars may be substituted in some laboratories. You may eat and drink normally 1 hour after the test has begun but no alcohol must be taken until the test is completed.

    All urine is to be collected for the next 6 hours into the container provider. At the end of this period you should try and empty the bladder to ensure that a full 6 hour collection is obtained. The completed container should be returned to the Department of Nuclear Medicine as soon as possible.

    After the test

    The urine is analysed for the amount of radioactive tracers present. Mannitol is normally absorbed completely and all of this should be excreted in the urine. EDTA is a larger molecule and does not pass through the healthy intestinal wall. It is therefore not absorbed into the blood stream and should not be present in the urine under normal circumstances. The damage to the small intestine is calculated from the amount of mannitol in relation to the EDTA in the collected urine. The results will be sent to your doctor who will decide what to do next.

    15. Leucocyte Scan

    This is a white cell scan performed in the Nuclear Medicine department of the hospital.

    It is a sophisticated test, valuable in determining the site, severity and extent of inflammation and highlighting complications such as abscesses.

    It is based on the function of the white blood cells, which is to travel to sites of inflammation and fight infection.

    There is no preparation prior to the test and you may eat and drink normally.

    The test is carried out in two phases:

    Phase 1

    A sample of your blood is taken (around 40 ml) and the white cells are separated from it. They are then labelled with a very small amount of a radioactive chemical (Indium III or TC99mHMPAO isotopes) and re-injected back into the bloodstream. This part of the test can take up to 2 hours.

    Phase 2

    The second part of the test is usually performed about 3 hours later and involves scanning the abdomen to trace the white cells, detectable because of the isotope. The images are produced on a screen and dark areas are seen at the site of inflammation.

    Occasionally, if an abscess is suspected, you may be recalled for scanning the next day.

    After the test

    A report of the scan will be made and sent to your doctor for review.

    16. Small Bowel Enema

    Barium sulphate is a liquid, which is opaque to X-rays and, therefore, shows up on film.

    In this examination it is administered through a tube to outline the small bowel.

    Preparation

    A laxative solution (1 sachet of Picolax) is given to clear out the bowel and a restricted diet is followed.

    Breakfast

    Boiled egg, White toast, Black tea or coffee

    Lunch

    White meat / White fish
    Boiled or mashed potatoes or rice
    (No vegetables)
    (No fruit)
    Fruit flavoured jelly / Plain yoghurt / Black tea or coffee / Fruit squash

    Supper

    Clear soup
    Fruit flavoured jelly
    Black tea or coffee
    Fruit squash
    You will be asked to eat or drink nothing for 6 hours prior to the time of the examination. You may take your usual medication.

    The Examination

    A soft, plastic tube is passed in through the nose and down the throat into the stomach and into the small bowel. A local anaesthetic spray into the nose or throat may allow a smooth and more comfortable passage of the tube.

    Barium liquid is then put down the tube and a series of X-rays is taken. Sometimes the barium is slow to pass into the small bowel and the procedure may take up to one hour.

    After the Test

    The radiologist can review the films and send a report to your doctor.

    If a local anaesthetic spray has been used, you should not eat or drink for two hours after the X-ray.

    A laxative is given following the procedure to allow the barium to be passed out of the bowel more easily, and your bowel motions will be white for the next few days.

    17. Ultrasound

    Ultrasonography is the production of images of the internal organs by passing very high-pitched sound waves into the body. These are inaudible to the human ear.

    The sound waves, on hitting the organs, produce 'echoes' which are built up into an image on a screen by a computer.

    Uses

    It is used in the detection of disease in the gall bladder, liver, pancreas, and kidneys e.g. stones, dilated ducts.

    Preparation


    1. Abdominal ultrasound
    You will be asked to have nothing to eat or drink for 6 hours prior to the procedure, but you may take your usual medication. If the gall bladder is being examined, the previous day's supper must have been fat-free.

    2. Pelvic ultrasound
    The bladder must be full so you should drink lots of fluid about 1 hour before the examination and not pass urine before the test. This ensures that the bladder is full and easily visible.

    The Examination

    Whilst lying comfortably on a couch, the radiologist will put some jelly on your abdomen and move a transducer (sound wave transmitter) over it. The examination takes about half an hour. A pelvic ultrasound often also involves a separate vaginal examination in which a small probe is introduced into the vagina which also transmits sound waves producing pictures on the screen. This is not painful but may feel a little uncomfortable.
    The radiologist can interpret these pictures and send a report to your doctor.

    After the Test

    You may eat and drink normally.

    18. CT and MRI scanning

    Computerised scanning which gives detailed layers of the body to show the organs in the abdomen and complications of the disease, e.g. abscesses and fistulae. CT scans use x-rays, but MRI scans (magnetic resonance imaging) use changes in the position of certain molecules in the body when it is exposed to powerful magnets. MRI is therefore particularly suitable for use in young patients with IBD who may need repeated examinations, for it does not increase the risk of causing cancer that X-rays do. Thus these investigations are rapidly replacing older tests such as barium x-rays in the evaluation of IBD. Not only do they give excellent views of the inflamed intestine, but they also provide information on adjacent organs which are not visible on barium studies.

    19. Malabsorption studies

    Certain nutrients may be absorbed poorly or not at all in CD or as a result of removal of part of the small intestine, particularly the terminal ileum. Tests carried out to show this might include:

    a) Faecal fat determination. To see if fat is being adequately digested it is sometimes necessary to collect the stools for 3 days in a suitable bucket provided by the laboratory. At the end of the collection the bucket is delivered to the laboratory. An increase in the amount of fat present suggests that digestion and absorption is inadequate.

    c) Glucose tolerance test. This is to test the absorption of a simple sugar which may be reduced in the presence of small bowel disease (or be increased in diabetes). After an overnight fast the patient has a blood test to measure the fasting blood glucose, and then swallows 75g glucose. Further blood samples over the next 3 hours follow the absorption of the sugar into the blood.