Another way doctors may investigate the general health of your bowel is by testing a sample of your stool (faeces). They can examine the sample for many indicators of intestinal disease, including the presence of blood, parasites and markers of intestinal inflammation.
One of the most exciting advances in the last few years has been the introduction of the new faecal calprotectin test. This can do away with the need for colonoscopy in many patients. New tests are being developed all the time and we keep up to date with these advances.
Taking the test
The standard stool sample needs to be only a very small amount. Collecting it is not much fun but it is not difficult. You will be given a pot with a lid. The lid has a little spoon attached. All you need to do is to ‘scoop some poop’ into the spoon and put in the pot. Not particularly pleasant, but not particularly terrible either! The stool can be hard, soft or watery. It does not matter. The sample can even be stored at room temperature and sent in the post for analysis.
Stool tests for infection
If the doctor suspects you might have a bowel infection, the best type of stool to send the laboratory is liquid or semi-solid. It also needs to be delivered to the hospital laboratory fresh. So if you produce your stool in the middle of the night, please put it in the pot and place it in a cold place. If you cover it, the fridge is an excellent place to store a sample for a few hours. As soon as the hospital laboratory is open, deliver it there directly.
Tests performed on stool for infection usually include looking for bacteria including E coli, Salmonella, Shigella and Campylobacter.
Stools may also be examined for parasites, ova and cysts. These are produced by many tiny organisms such as Giardia lamblia, which is an important cause of intermittent diarrhoea.
Other organisms which are sometimes found include Blastocystis homini for example. It is not clear whether this particular organism is the cause of disease or not. You would have to discuss with your doctor whether you should take treatment for this or not.
Stool tests for inflammation – faecal calprotectin
One key element that the laboratory can measure in stool samples is the level of a certain protein, called calprotectin.
Your white blood cells, key components of inflammation, produce calprotectin; if there is inflammation in your bowel, there is likely to be an increase in the number of white blood cells, which in turn leads to an increase in production of this calprotecin. Doctors can therefore use this test as a general measurement of inflammation in your bowel.
This test can be really useful for identifying whether a patient is likely to have inflammation in the bowel (such as Crohn’s disease or ulcerative colitis) or irritable bowel syndrome.
This is the first of a whole new generation of tests, which will allow doctors to diagnose your disease without doing invasive procedures such as colonoscopy or sigmoidoscopy. If the faecal calprotectin level is normal, it is very likely that you do not have inflammation in your bowel. It may be possible, with a normal test, to avoid having a colonoscopy.
Stool tests for Helicobacter pylori
Helicobacter pylori is a bug (bacteria) that lives in the stomach. It causes stomach ulcers, and, in a small number of people, stomach cancer.
Helicobacter can cause abdominal pain. If you are suffering from this, it is worth making sure that you don’t have this bug in your stomach. If you do, a special course of antibiotics can get rid of it for you.
Stool samples are the best way to check for Helicobacter pylori.
Tests for occult blood in stool
If you see blood in your stool, you know that you must go and see a doctor. But what happens if you only bleeding a very small amount? You won’t see it, but it can be detected in stool samples. This is the reason that the UK has a national bowel cancer screening programme which tests the stool for a tiny amount of blood. This is occult blood– that is, you cannot see it.
If you have occult blood in your stool, you need a colonoscopy.
The only problem with faecal occult blood tests is that they are not very sensitive. So, although a positive test means that you are bleeding, a negative faecal occult blood test does not mean that you are not bleeding! Always check with a medical expert if you have symptoms or are unsure what tests you need to have done.
