Irritable bowel syndrome

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at January 30, 2016
StartDiseasesIrritable bowel syndrome

Irritable bowel syndrome, or IBS, is a bowel disorder that affects about one out of every 10 adults. The cause of IBS is unknown, but it is sometimes called a brain-gut disorder, intimating that brain activity, especially stress, triggers the reaction in the bowels. IBS is the second most common reason for people missing work after the common cold.


Definition & Facts

Irritable bowel syndrome is more common in women, affecting two out of three in the 10 to 15 percent of the U.S. population who have it. Men suffer a slightly lower rate at one out of three. IBS is characterized by various bowel symptoms including pain, bloating, diarrhea, constipation and gas.

Stress is not the cause of IBS, but it can aggravate the symptoms. Some IBS sufferers are largely functional, while others are extremely impaired by the symptoms. The symptoms of IBS are unpredictable and can come and go. Some sufferers may only experience diarrhea, while others may only experience constipation. Sometimes diarrhea and constipation alternate.

Symptoms & Complaints

The symptom cluster of IBS may seem random at first, but there is a pattern. One key symptom to recognize is abdominal pain or discomfort. The pain may be dull and aching, or it might be sharp and feel like cramps. The pain is often relieved by a bowel movement. The other key IBS symptom is the change in bowel habits. This may be going more often, as in diarrhea, or it might be going less, as in constipation. The two symptoms can also alternate.

Up to half of IBS sufferers also report other gastrointestinal disturbances such as heartburn, bloating, nausea and fullness. Some other symptoms include feelings of urgency and incomplete emptying. Some non-gastrointestinal symptoms may manifest as well. These include fatigue, muscle aches, headache, lower back pain and sleep problems.

Though IBS produces a range of symptoms, it is not typically associated with blood in stools, fever or unintentional weight loss. IBS symptoms can also be associated with other medical problems and patients over 50, those who have recently used antibiotics and those experiencing night symptoms should consult their doctor to rule out other issues. A history of cancer or change in symptoms, such as a new pain, should also be investigated.


The exact cause of IBS is unknown, but there are some risk factors that can lead to the condition. One of these is acute gastroenteritis. It is estimated that about 10 percent of IBS diagnoses come after a gastroenteritis infection. The infection and accompanying stress and anxiety cause changes in the bowel that tend to manifest as diarrhea.

Even though stress is not thought to be a direct cause of IBS, the link is inevitable considering the high levels of anxiety present in IBS sufferers. Two-thirds of sufferers have some type of anxiety or other mental disorder prior to IBS onset.

Another possible cause is small intestinal bacterial overgrowth, or SIBO. It typically manifests as diarrhea-prominent, but can also show up as constipation. Protozoan infections tend to happen more often with IBS-D patients, but can also mirror the symptoms of IBS in otherwise healthy individuals. Blastocystis hominis and dientamoeba fragilis have both been linked with IBS. Candida albicans, which is a type of yeast has been found at abnormally high levels in some IBS patients.

Diagnosis & Tests

Diagnosis of IBS can only be done by a physician and begins by ruling out other more serious conditions. The physician will look for the specific symptoms of IBS, perform a physical examination and initiate various diagnostic testing to look for other causes. Getting a diagnosis of IBS can be a form of relief to patients when they know that nothing serious is causing their symptoms. For patients, the most important thing is to have a clear description of symptoms.

Doctors may do blood tests, stool tests, a colonoscopy, barium enema and psychological tests to rule out other causes and find agreement with the IBS profile.

Doctors may also ask about and look for various red flags associated with more serious conditions masquerading as IBS. Some red flags include blood in stool, fever, history of cancer, onset at age 50 or older, weight loss, anemia and antibiotic use.

Some IBS sufferers may experience the condition alongside other conditions such as depression, anxiety, fibromyalgia, gynecological conditions and urinary problems among others.

Treatment & Therapy

Treatment of IBS often involves treatment of the symptoms, whether diarrhea, constipation, gas or pain. Probiotics are useful in treating abnormal gut bacteria, while antispasmodics may work for pain. Peppermint oil is sometimes recommended after eating for pain, but it does not work for everyone.

For constipation, an increase in fiber can help, but sometimes a laxative is needed. Neither of these treatments help the pain factor. Diarrhea may be treated with loperamide. Gas and bloating can be helped through diet or taking anti-gas medications. Heartburn can be relieved by antacids.

Diet changes are also commonly used to treat IBS. One common diet employed by IBS sufferers is known as a low-FODMAP diet. FODMAP stands for fermentable oligo-saccharides, di-saccharides, mono-saccharides and polyols. These are short-chain carbohydrates that tend to negatively affect those with IBS. These types of carbohydrates are rapidly consumed by gut bacteria and cause intense gas. Studies have shown the low-FODMAP diet can reduce symptoms for approximately 75%-85% of IBS patients.

Prevention & Prophylaxis

Because IBS is more of a collection of symptoms than a distinct disease, it is difficult to prevent entirely. Taking probiotics, maintaining a healthy diet and managing stress can help prevent IBS. Stress is the hardest to avoid, and relaxation therapy and hypnosis are often recommended as ways to deal with anxiety and stress.