Irritable bowel syndrome (IBS) is a disease of exclusion, meaning that a diagnosis of IBS is often given after no other cause for the symptoms can be found. This also means that IBS is frequently misdiagnosed, and treated, as other conditions. Some people may see several different doctors and undergo many tests before finally arriving at a diagnosis at IBS. What are the other conditions that have symptoms similar to IBS? These conditions are known as “differential diagnoses” -- different diseases that have a similar set of symptoms or “presentation.”
Differential: Inflammatory bowel disease (IBD)IBS is often confused with ulcerative colitis or Crohn's disease (collectively known as IBD), but there are differences. IBS is a syndrome, not a disease, and it will not lead to colon cancer nor does it cause intestinal bleeding. IBD will often cause inflammation or ulcers in the intestinal wall that can be seen by a physician during a colonoscopy, while IBS does not have any such physical signs. IBD can also cause severe abdominal pain, fevers, and weight loss.
Key points: IBS does not cause inflammation, ulcers, bleeding, or significant weight loss.
Differential: Celiac disease.Celiac disease (sometimes called celiac sprue) is reportedly underdiagnosed as many people still think that this is a rare childhood condition. In fact, as many as 1 in 1000 people may have this hereditary condition. It may take years to get a diagnosis of celiac disease, as the symptoms are often vague and may be overlooked or assumed to be caused by other conditions. When a person with celiac disease eats gluten (a common food ingredient), an immune response is triggered that causes damage to the lining of the small intestine. This results in the small intestine being unable to absorb critical nutrients. Unlike IBS, for which there is no diagnostic test, celiac disease can be diagnosed with 85% to 90% accuracy with antibody tests (IgA anti-gliadin and anti-tissue trans glutaminase), and with 95% to 98% accuracy with genetic testing (HLA-DQ2 and HLA-DQ8 genes). The basis for the treatment of celiac disease is the elimination of gluten from the diet. It is estimated that as many as 30% of those diagnosed with IBS may actually have celiac disease.
Key points: Celiac disease can often be accurately diagnosed with antibody tests or genetic testing, and symptoms often improve rapidly with a gluten-free diet.
Differential: Infection.A viral, parasitic, or bacterial infection can cause the symptoms common in IBS such as abdominal pain, bloating, and diarrhea. These infections may be the common “stomach flu” (viral gastroenteritis), food poisoning, or from water contaminated with harmful parasites. These types of infections tend to be acute rather than chronic; the symptoms start quickly and may be severe. In many cases there may be a clear event that precipitated the symptoms, such as eating undercooked food (in the case of food poisoning), or having contact with a person with similar symptoms (such as with the stomach flu). There is some evidence that IBS may be connected with a bacterial infection, but this theory is not yet proven.
Key points: Bacterial and parasitic infections often improve after treatment with antibiotics, and viral infections tend to improve after a few days, while symptoms of IBS are chronic.