Irritable bowel syndrome
IBS
The short answer
A symptom-based diagnosis made against published criteria once other explanations have been considered. There is no test that confirms it. That is a design feature of the definition rather than a shortcoming of the workup.What is not settled
Because it is defined by exclusion, whether you end up with this label depends partly on which other things were looked for and which tests were run before you got it. That is why so many people end up carrying this label alongside a second one, and why the question of which came first is usually unanswerable.
What it gets confused with
Each of these takes one pair and separates them on what can actually be measured.
- Is it IBS or a food intolerance?
Three things get called a food reaction: immune allergy, enzyme deficiency, and fermentation. They need different tests, and one common panel is not one.
- Is it IBS or MCAS?
IBS is a gut diagnosis of exclusion. MCAS is a systemic one. If your symptoms leave the gut, that is the observation that matters most here.
- Is it IBS or SIBO?
IBS is a diagnosis of exclusion. SIBO is a test result. That difference explains why people carry both labels, and why the two breath tests disagree.
Where this sits on the site
This page is an index rather than an article. It exists so that a label has one place to start from, and so the 3 pages above are reachable without knowing which section we filed them under. The pages themselves are where the work is.
Common questions
- Is this page a diagnosis of IBS?
- No. Nothing here can tell you what you have. What these pages do is show you what separates one label from another, what each test can physically measure, and where the published sources disagree, so that the conversation you have with a clinician is a better one.
- What is genuinely unsettled about IBS?
- Because it is defined by exclusion, whether you end up with this label depends partly on which other things were looked for and which tests were run before you got it. That is why so many people end up carrying this label alongside a second one, and why the question of which came first is usually unanswerable.
Related
- Small intestinal bacterial overgrowthAn overgrowth of bacteria in the small intestine, diagnosed in practice by a breath test that measures gases rather than bacteria. Where that gap matters, and what it does not rule out.
- Mast cell activation syndromeA syndrome with two competing sets of diagnostic criteria that do not agree. What each one requires, what that disagreement means for you, and what it overlaps with.
- Histamine intoleranceA proposed reaction to dietary histamine with no agreed confirmatory test. Why the published food lists contradict each other, and what the blood test does and does not show.
- Food intoleranceA reproducible reaction to a food that does not use the immune mechanism of an allergy. Which means the common tests are answering a different question.