Digestive Disorders > IBS

Irritable bowel syndrome – How is it diagnosed?

Dr. med. Andre Sommer

Dr. med. Andre Sommer

Irritable bowel syndrome is not a life-threatening disease, but the diagnosis can still be very stressful for those affected. Since there are no specific physical causes for irritable bowel syndrome, the diagnosis is sometimes unnecessarily repeated with different doctors. If the person concerned goes to several doctors in the same specialist area in a short time without them knowing each other, the term “doctor hopping” is used (sometimes in a derogatory way).

In the United States alone, over $30 billion in health care costs arise primarily from irritable bowel diagnostics. Since there are comparatively few effective irritable bowel medications, only about six percent caused of the costs are due to medication. The remainder is made up of, among other things, productivity and work losses as well as visits to the doctor.

Doctors and patients are therefore encouraged to jointly carry out extensive and understandable diagnostics for the patient. This is the only way to remove uncertainties and create trust in the patient-doctor relationship. And this is the basis for the successful treatment of irritable bowel syndrome. The trust between patient and doctor is very important during the therapy, which sometimes lasts for years.

How is irritable bowel syndrome defined?

In Germany, the diagnostic standards are set by the S3 guideline on irritable bowel syndrome. The S3 guideline has replaced the Rome III criteria of 2006. According to the German guidelines, irritable bowel syndrome is present if the following three points are met:

  • There are chronic symptoms (e.g. abdominal pain, flatulence) that last longer than three months and are related to the intestine by the patient and doctor and are usually accompanied by changes in bowel movements.
  • The symptoms should either be the reason that the patient is seeking help or worried, or they should be so severe that the patient's quality of life is significantly affected.
  • The prerequisite is that there are no changes characteristic of other clinical pictures, which are probably responsible for these symptoms.

What are the basic elements of the diagnosis of “irritable bowel syndrome”?

Two things are crucial for the diagnosis of irritable bowel syndrome:

  1. Medical history: Patient and doctor clarify the pattern and extent of the complaints together. The triggers, duration and timing of irritable bowel symptoms are recorded. Digital or analog symptom and nutrition diaries help with the medical history.
  2. Exclusion of other causes: Even though many physical changes in irritable bowel syndrome patients have been measured in studies, there is still no defined finding to prove the diagnosis of irritable bowel syndrome with certainty. Therefore, irritable bowel syndrome diagnosis is an exclusion diagnosis, in which other diseases (differential diagnoses) with similar symptoms have to be clarified beforehand. It is also important to diagnose life-threatening diseases when diagnosing irritable bowel syndrome. In addition to a colonoscopy, a general physical and possibly a gynecological examination should be carried out. In addition, ultrasound, blood, stool and urine tests have proven their worth. Food intolerance can also be specifically identified in connection with a symptom diary.

What diseases are excluded when diagnosing irritable bowel syndrome?

Not every suspected diseases has to be ruled out for irritable bowel syndrome (differential diagnoses). Rather, irritable bowel diagnosis is based on the main symptoms. There are four groups:

  1. Diarrhea as a main symptom
  2. Constipation as a main symptom
  3. Pain as a main symptom
  4. Flatulence and bloating (abdominal distension) as the main symptoms

The following table shows a selection of diseases (differential diagnoses) that, depending on the main symptom, should be excluded from the diagnostic process before the diagnosis of irritable bowel syndrome can be made:

Symptom Important differential diagnoses
Diarrhea Intestinal infection with bacteria, viruses, fungi or parasites
Small Intestinal Bacterial Overgrowth (SIBO) colonization
Chronic inflammatory bowel diseases such as Crohn's disease, ulcerative colitis, celiac.
Carbohydrate malabsorption (e.g. lactose, fructose and sorbitol)
Diabetes mellitus / exocrine pancreatic insufficiency
Food allergy
Side effects of medication or laxative abuse (laxative abuse)
Colon cancer
Constipation Side effects of drugs (e.g. opiates, anticholinergics, antihypertensives, antidepressants)
Underactive thyroid (hypothyroidism) or underactive parathyroid gland (hypoparathyroidism)
Colon cancer
Bulges in the intestine (diverticular disease)
Pain Crohn's disease
Colon cancer
Ovarian cancer (ovarian tumor)
Narrowing of the small intestine (stenosis)

Pain disorder after abdominal surgery

Bloating Improper colonization of the small intestine (SIBO)
Carbohydrate malabsorption
Pain disorder after abdominal surgery
Intolerance to fermentable carbohydrates (FODMAP intolerance)

Nerve or muscle diseases can also be responsible for similar symptoms. These include:

  • Hirschsprung's disease
  • Chronic intestinal pseudo-obstruction (CIPO)
  • Acute colonial pseudo-obstruction (ACPO, “Ogilvie syndrome”)
  • Idiopathic megacolon or megarectum (IMC)
  • Slow transit constipation
  • Anorectal dysfunction (e.g. pelvic floor dyssynergy, anism, pelvic floor spasticity)
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What is part of the basic diagnosis of irritable bowel syndrome?

In addition to the diagnosis explained above based on the main symptoms, the guidelines generally recommend a large blood count and the determination of the inflammatory marker CRP and the blood sedimentation rate (BSG). A colonoscopy should also be done. Depending on the main symptom, the following examinations can then follow:

  • Concentrations of blood salts (electrolyte concentrations), kidney retention values, liver and pancreatic enzymes
  • TSH (thyroid hormone)
  • Blood sugar and HbA1c (long-term blood sugar value)
  • Stool microbiology (especially for diarrhea)
  • Celiac disease antibodies (Transglutaminase-Ab)
  • Calprotectin A / lactoferrin in stool
  • Hydrogen breath test (H.2breath test)

How certain is the diagnosis of irritable bowel syndrome?

In about five out of a hundred people diagnosed with irritable bowel syndrome, it turns out within the next six years that the symptoms have another (organic) cause that leads to a digestive system disorder. As a result, patients with irritable bowel syndrome misdiagnosis are sometimes treated incorrectly for years. With the right examinations, this risk can be greatly minimized.

Can irritable bowel syndrome change over time?

After the initial diagnosis, the course of irritable bowel syndrome was followed in studies and results were obtained that differed relatively widely individually. The symptoms worsen in one out of ten, and three to five have an unchanged diagnosis of irritable bowel syndrome with the same symptoms. In the rest of those affected with an initial diagnosis of irritable bowel syndrome, the symptoms improve or disappear entirely.

Can the diagnosis irritable bowel syndrome also hide chronic inflammatory diseases?

Yes, the symptoms of inflammatory bowel disease (e.g. Crohn's disease and ulcerative colitis) and those of irritable bowel syndrome are similar in many cases. As a result, some patients with inflammatory bowel disease are wrongly diagnosed with irritable bowel syndrome. A colonoscopy in combination with a stool and blood test can rule out chronic inflammatory bowel disease in almost all cases.

How many celiac patients are wrongly diagnosed with irritable bowel syndrome?

Even those affected by celiac disease (an intolerance to the wheat gluten gluten) are sometimes first diagnosed with irritable bowel syndrome. This is due to the fact that about three out of four people with celiac disease, like the majority of irritable bowel patients, suffer from abdominal pain and flatulence. In half of these people, irritable bowel syndrome is misdiagnosed and irritable bowel diagnosis is incorrectly maintained in the long term.

About a third of people get a mental disorder as a misdiagnosis. This then leads to a mental illness being treated by the doctor, although in reality celiac disease has an organic cause for the symptoms. It takes more than ten years for every fifth patient to realize that a disease other than irritable bowel syndrome is actually the cause of the complaints.

Can colon cancer be behind an irritable bowel diagnosis?

Colon cancer, also called colorectal cancer, is one of the most common types of cancer. It has been shown that colon cancer occurs within one year after about one in a hundred diagnoses of irritable bowel syndrome. This rate is higher than that of the general population and suggests that in rare cases, irritable bowel cancer can actually be hidden behind the diagnosis of irritable bowel syndrome. For this reason, correct irritable bowel diagnosis includes the exclusion of colon cancer by colonoscopy. However, everyday clinical practice shows that doctors do not always adhere to the recognized diagnostic guidelines and sometimes prematurely diagnose irritable bowel syndrome.

Can the symptoms of irritable bowel syndrome be confused with those of ovarian cancer?

Almost nine out of ten women with ovarian cancer have symptoms that can also occur with irritable bowel syndrome. A comprehensive gynecological examination by a gynecologist is therefore always essential for correct irritable bowel syndrome diagnosis in women.

Can the diagnosis of irritable bowel syndrome hide a mental illness?

Gastrointestinal complaints can also occur or get worse as part of mental illness. If there is a suspicion of such a connection, it is recommended to seek psychological, psychiatric or psychosomatic support in order to specifically identify and treat mental illnesses such as anxiety disorders or depression. Mental disorders do not have to be the sole cause of irritable bowel syndrome, but often occur together with it.

What to do after a diagnosis of irritable bowel syndrome

Irritable bowel syndrome is an often stressful, but fundamentally harmless disease that affected people can deal with properly and responsibly through proper management.

There are several effective treatment options that doctors can prescribe for irritable bowel syndrome. The choice of the right therapy depends on which problem is in the foreground (abdominal pain, constipation, diarrhea, flatulence) and can include classic medication, herbal supplements or a change in diet.

Many patients feel good knowing about their illness. Here, self-help groups are a useful support, but also high-quality information on the Internet or apps make it easier for those affected to deal with the disease. It can also help to deliberately involve loved ones in the therapy. They can then help the patient keep to nutritional or medication plans and are often an important support.

El‐Serag, H.B., Pilgrim, P. and Schoenfeld, P., 2004. Natural history of irritable bowel syndrome. Alimentary pharmacology & therapeutics, 19(8), pp.861-870. Online: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2036.2004.01929.x/epdf , accessed on 24.01.2016

Layer, P., Andresen, V., Pehl, C., Allescher, H., Bischoff, S.C., Classen, M., Enck, P., Frieling, T., Haag, S., Holtmann, G. and Karaus, M., 2011. S3-Leitlinie Reizdarmsyndrom: Definition, Pathophysiologie, Diagnostik und Therapie. Gemeinsame Leitlinie der Deutschen Gesellschaft für Verdauungs-und Stoffwechselkrankheiten (DGVS) und der Deutschen Gesellschaft für Neurogastroenterologie und Motilität (DGNM. Z Gastroenterol, 49(2), pp.237-293. Online: http://www.dgvs.de/fileadmin/userupload/Leitlinien/Reizdarmsyndrom/LeitlinieReizdarmsyndrom.pdf, downloaded on 23.01.2016.

Drossman, D.A. and Dumitrascu, D.L., 2006. Rome III: New standard for functional gastrointestinal disorders. Journal of Gastrointestinal and Liver Diseases, 15(3), p.237. Online: http://www.jgld.ro/2006/3/5.html, downloaded on 23.01.2016.

Dr. med. Andre Sommer

Dr. med. Andre Sommer

I’m André, a medical doctor from Berlin. Together with a team of medical doctors, nutritionists and data scientists we empower people to understand digestive issues with our app Cara.

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