Introduction to IBS: Symptoms, Diagnosis, and Testing
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Irritable bowel syndrome (IBS) affects at least 10–15% of adults. It’s prevalent around the world. IBS is associated with a significant healthcare and economic burden. Studies have shown that IBS patients have an increased number of outpatient healthcare visits, diagnostic tests, and, surgeries. IBS can severely compromise a person’s quality of life. It is second only to the common cold as a cause of absenteeism from work.
Here you will find information on IBS symptoms, causes, and treatment options. Hopefully this will help you find proper care and deal most effectively with your condition.
What is IBS?
IBS is a long-term or recurrent disorder of gastrointestinal functioning. It usually involves disturbances in the large intestine (colon) and small intestine. The disturbances involve:
- motor function (motility),
- sensation, and
- secretion.
These intestinal/bowel (gut) related activities are regulated by the brain. This regulation may also be impaired. That's why IBS is often called a brain-gut disorder.
The disturbances can produce symptoms of:
- abdominal pain or discomfort,
- bloating or a sense of gaseousness, and
- a change in bowel habits (diarrhea and/or constipation).
The Most Common Symptoms of IBS – Abdominal pain and/or discomfort is the key symptom of IBS. It is often improved with a bowel movement. There are many causes for abdominal pain. In IBS the pain or discomfort is associated with a change in bowel habits (diarrhea and/or constipation).
Symptoms can change over time. There can be periods when symptoms flare up as well as periods of remission when they diminish or disappear. The main bowel habit can vary over time, alternating between constipation and diarrhea.
Other Common Symptoms of IBS – Other symptoms of IBS include:
- bloating (a sensation of fullness in the belly),
- urgency (the need to use a restroom in a hurry),
- mucus (white or yellow liquid) in the stool, and
- the sensation of incompletely passing stools.
How is IBS Diagnosed?
Recognizing IBS – The typical features of IBS are generally recognizable by a physician. Usually the physician will examine the abdomen of a patient with IBS and it will be normal or have tenderness. A rectal exam is also done to look at how the rectal floor muscles function. This is especially important if there is incontinence or severe constipation with straining. The first steps are to confidently recognize the diagnosis of IBS and remove the suspicion of other diseases. Read more about IBS Symptoms
Making the Diagnosis – The first step in making a positive diagnosis of IBS is for the doctor or other healthcare provider to see if the symptoms of IBS are present. This is best determined by the use of the Rome Criteria, a collection of the most common symptoms that typify IBS. This includes abdominal pain or discomfort for several months that is associated with two of the following:
- the pain or discomfort is relieved by defecation,
- the pain or discomfort is associated with an increase or decrease in stool frequency, and/or
- the pain or discomfort is associated with the stools becoming harder or softer in consistency.
Symptoms of Something Else – The next important step is to look for signs and symptoms that suggest a condition other than IBS, such as inflammatory bowel disease, colon cancer, or celiac disease. These signs and symptoms are referred to as “alarm signs” or “red flags.” They include:
- anemia and other abnormal blood tests,
- blood in the stool,
- unexplained weight loss,
- fever,
- new onset of symptoms at the age of 50 or older, and
- family history of inflammatory bowel disease, colon cancer, or celiac disease.
These alarm signs usually do not occur because of IBS. They suggest other medical problems. When these symptoms occur, you should tell your doctor right away. Read more about IBS Diagnosis
What tests are appropriate to confirm irritable bowel syndrome, and exclude other significant disease?
If your doctor suspects you have IBS, an evaluation will follow. This will vary from person to person. It will depend on your:
- symptoms,
- age, and
- overall health, as well as the health care practices of your physician.
The starting point of the diagnosis is a detailed history to identify the characteristic symptoms of IBS, and a physical examination.
There is no test for IBS. Lab blood and stool tests, x-rays, and endoscopic procedures (e.g., colonoscopy) are used to rule out other diseases of the bowel, which can present with similar symptoms. These tests are usually normal in people with IBS.
If you have symptoms compatible with IBS and no alarm signs recent studies suggest that few tests, if any, are needed. However, sometimes additional testing should be considered. This is especially the case if you have mostly diarrhea or diarrhea mixed with constipation.
- A colon examination, such as a colonoscopy, at or above the age of 50 if you have not had one previously – not as a test for IBS, but as a screening test for colon polyps and cancer. Done for these purposes, biopsies or very small samplings of the lining of the colon (large intestine) are recommended. These tissue samplings can determine if microscopic colitis or mild inflammation of the colon is present. In this condition, the colon can appear normal to the naked eye, but there are changes in the tissue that can be seen under a microscope. This condition can mimic symptoms of IBS (abdominal discomfort and diarrhea) but may be treated differently than IBS.
- A blood test for celiac disease. This is a genetic condition of the small intestine which develops in persons intolerant to gluten. Gluten is a common ingredient in many foods including most grain and cereal foods as well as many processed foods. Gluten intolerance results in symptoms similar to those seen in IBS. If the blood test is positive, an endoscopy to examine and biopsy the small intestine confirms the diagnosis.
- A test for lactose intolerance. If dairy product intolerance remains a concern despite dietary changes, a lactose breath test can be performed to confirm this diagnosis.
Importantly, even if another diagnosis is made, it may exist along with a diagnosis of IBS. The physician will then need to decide which condition or conditions are to be treated and how.
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Adapted from IFFGD publication #101 revised and updated by: Lin Chang, MD, UCLA School of Medicine, Los Angeles, CA, and Douglas A. Drossman, MD, University of North Carolina, Chapel Hill, NC