Overview of investigations in Crohn’s disease

Investigations (tests) 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
a) to check for anaemia
b) to check if there is an imbalance of salt and water due to diarrhoea or steroids
c) to check the proteins in the blood
(i) a low level of albumin suggests severe ulceration. It can also cause the ankles to swell.
(ii) a raised C-Reactive Protein reflects inflammation
d) to check the condition of the liver.
e) to check for anaemia and number of white blood cells and platelets which may be raised in presence of inflammation

2. Stool tests
A relapse may sometimes be due to an infection of the gut caused by bacteria, which can be detected in the stool. Calprotectin in the stool may reflect an increase in intestinal inflammation.

3. Sigmoidoscopy
This is an examination of the lower bowel with a rigid metal tube that has a light on the end. Small pieces of tissue called biopsies may be taken for examination under the microscope.

4. Abdominal x-ray
Straight x-ray of the abdomen may show dilatation (swelling) or obstruction of the bowel or reveal the presence of constipation.

5. 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.

6. Colonoscopy
An examination, in which the large intestine (colon) is examined by a long, flexible, fibre optic telescope called a colonoscope. Biopsies may be taken.

7. White cell scan (leucocyte scan)
A scan in which the patient’s own white blood cells, labeled with a tiny amount of radioactivity, are used to show the extent and severity of inflammation.

8. Ultrasound scan
A scan in which very high-pitched sound waves, inaudible to the human ear, are transmitted into the body from a transducer placed on the abdomen. These produce echoes on hitting an organ and are transformed into pictures by the computer. This test is used commonly to detect complications involving the liver and gall bladder, e.g. stone or dilated ducts.

9. Breath test
The amount of hydrogen is measured on the expired breath following a sugar drink. An increased amount of hydrogen suggests bacteria in the small intestine have built up due to the presence of strictures.

10. 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.

11. Malabsorption studies
Certain nutrients may be absorbed poorly or not at all in Crohn's disease 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) Dicopac or Schilling test for B12 absorption. This involves an injection of B12 and collection of urine for 24 hours.
b) Intestinal permeability test. A sweet drink containing a mixture of sugars is given and the urine collected for 6 hours to see how much sugar appears in the urine.

From time to time progress will be monitored and response to treatment by means of the 'Harvey & Bradshaw Index.' This is a simple scoring system to monitor disease activity taking into account a number of symptom markers over the previous 24 hour period, i.e.

a) General well-being
b) Number of liquid stools
c) Presence of abdominal masses
d) Abdominal pain
e) Any associated complications

A score of 3 or less is taken as remission. A score of 6 or more signifies a relapse. This system is a modification of another system called the Crohn's Activity Index (CDAI) which is still used in clinical trials. Similar symptom markers are used, but symptoms are only monitored over a period of a week.