Whilst there aren't specific TESTS FOR IBS, your hospital doctor may consider blood and stool lab investigations in confirming the diagnosis.
An endoscopic test may be offered, particularly if your symptoms are not typical of the Irritable Bowel Syndrome or if you have risk factors for other diseases such as bowel cancer.
If there is any relationship to food, you might also need a food intolerance assessment.
Your family doctor will likely refer you to a hospital Gastroenterologist for an opinion as they have access to investigations such as a colonoscopy, flexible sigmoidoscopy, CT-colonography and ultrasound.
Initially, your doctor will take a history of your complaint, perform an examination which might include a rectal examination (a finger examination of your back passage and a rigid Sigmoidoscopy - passing a rigid tube through your anus to look inside the back passage and assess the lining in your lower bowel or rectum).
Whilst there is NO SPECIFIC IBS BLOOD TEST, your doctor may do some blood tests to exclude other conditions such as celiac disease (by performing a celiac antibody blood test - see celiac disease), check for anaemia which can occur in conditions such as bowel cancer and inflammatory bowel disease and other investigations that they feel will help in making a diagnosis.
They will probably send stool samples to determine if there is a bacterial or parasite infection (see IBS or a parasite) causing your symptoms. They may also check a faecal calprotectin level, a substance that is present in your stool when bowel inflammation is present.
Acid reflux (often associated with weight gain) is quite common and may need further investigation with gastroscopy, a flexible camera examination of your upper gastrointestinal tract.
They might also consider food precipitants for your symptoms and want to exclude lactose intolerance .They do this by performing a lactose tolerance test.
An intolerance to gluten and SIBO or small intestinal bacterial overgrowth (see small intestinal bacterial overgrowth) are other considerations.
The need for FURTHER TESTS for IBS symptoms really depends on age and clinical indication. These will be carried out if there are any concerns about pathological causes for your symptoms such as bowel cancer, diverticular disease or inflammatory bowel disease.
The most common investigations done are:
FLEXIBLE SIGMOIDOSCOPY - passing a flexible camera into the left side of the large bowel to assess the lining (learn more about flexible sigmoidoscopy)
COLONOSCOPY - (see colonoscopy) a flexible camera passed into your large bowel through the anus (entrance to your back passage), with the intention of assessing the whole of your large bowel or colon to the caecum or terminal ileum. You can see colonoscopy pictures here .
BARIUM ENEMA - a barium enema is performed by passing a special dye through the back passage which shows up on x-ray.
CT COLONOGRAPHY - (see CT colonography) is used to assess the large bowel and is often reserved in cases where colonoscopy would be risky or technically not possible
ULTRASOUND - an examination that uses sound waves to highlight your abdominal organs
The more invasive your test, the higher the risk of having it done. However, when there are issues such as weight loss or rectal bleeding, investigations really are necessary.
If you are a woman, ovarian cancer and endometriosis can sometimes mimic IBS symptoms and may need to be excluded.