Irritable Bowel Syndrome

Irritable Bowel Syndrome

The term “irritable bowel syndrome” refers to a number of different conditions with abdominal symptoms whose physical causes are difficult or even impossible to detect.


Irritable bowel syndrome (IBS) is a highly-variable, chronic disease that is widespread in the Western world. The symptoms of irritable bowel syndrome include problems with digestion and bowel movements (such as diarrhea and/or constipation) that may alternate back and forth. As it is very difficult to identify a physical cause for the abdominal symptoms, irritable bowel syndrome is classified as a so-called functional disorder. Because these symptoms often change back and forth, IBS was previously sometimes referred to as “nervous colon”.

Irritable bowel syndrome is one of the most common gastrointestinal disorders. However, it is difficult to determine exact figures since the condition is often hard to diagnose due to the wide range of symptoms patients may experience. It is estimated that about 15% of the population suffers from IBS, with a somewhat higher frequency among women than men. The disorder can start at almost any age, including childhood and adolescence.

Scientists still do not completely understand what triggers irritable bowel syndrome, hence it may be difficult to pin down the exact causes of an individual case. Some potential causes that have been proposed are increased sensitivity (hypersensitivity) of the digestive tract and disrupted nervous system signaling in the gut. Furthermore, the barrier function of the intestines is weakened in irritable bowel syndrome with increased permeability of the intestinal wall, especially in people with diarrhea-predominant IBS.

The abdominal issues might also be triggered by changes to the “gut immune system” and/or by imbalances in certain signaling molecules (neurotransmitters). Other possible causes of IBS include an altered composition of the bacteria in the intestines (microbiota) or inflammation of the digestive tract, especially due to an infection. The intensity of the symptoms of irritable bowel syndrome is often enhanced by psychological factors and stress, although stress has so far not been shown to be a direct cause of the disease.

The symptoms of IBS vary greatly, and quite different symptoms may even occur at the same time. The intensity of the symptoms can also vary. The characteristic symptoms of IBS include abdominal pain and cramps, which are often associated with digestive issues such as diarrhea or constipation.

Other common symptoms of IBS are more frequent bowel movements, a sensation of incomplete bowel evacuation, bloating, and gas. The intensity of these symptoms can change over the course of the day and they usually go away completely at night. Irritable bowel syndrome (IBS) is divided into four different types depending on the main symptom: constipation-predominant IBS (IBS-C), diarrhea-predominant IBS (IBS-D), a mixed type alternating between constipation and diarrhea (IBS-M), and untyped IBS that does not fit into any of the other categories (IBS-U).

IBS patients often feel a heavy burden from their symptoms, which can have a major impact on their quality of life. The psychological stress of the disease may be so great that some patients develop depression.


Irritable bowel syndrome is diagnosed based on two factors:

  • evaluating the complete picture of all symptoms, and
  • ruling out other possible causes of these symptoms.

There are a number of diagnostic criteria and signs that may point to IBS. These include both the symptoms described above as well as general discomfort in the digestive tract that does not directly feel painful.

Another indication of irritable bowel syndrome is when symptoms improve after going to the bathroom (bowel movement). Other key criteria used to diagnose IBS are making sure that no physical cause of the symptoms can be found and ruling out other possible conditions. 

The process of diagnosing irritable bowel syndrome starts with the collection of a patient’s complete medical history (anamnesis) by a doctor. It is crucial to determine which of the digestive or abdominal symptoms are the primary ones, when they occur, and whether there is any link to practical factors such as diet, stress, or psychological difficulties. A patient must describe their symptoms – like stool frequency or consistency – as accurately as possible, including paying attention to what order the symptoms occur in. It may be helpful to keep a diary to track when each symptom occurs and how intense it is.

As part of the medical history, the doctor will also ask about any “red flags” that might point to other conditions. For example, bloody stools and anemia can suggest gastrointestinal bleeding, whereas unwanted weight loss may potentially be a sign of colorectal cancer. Other red flags include very intense and sustained pain, frequent vomiting, fever, and unusually decreased stamina.

In addition to collecting a medical history, the doctor will also perform a physical examination that includes pressing against the abdomen and drawing blood. The abdomen is also usually examined by ultrasound. For patients with irritable bowel syndrome, this physical examination typically does not provide any obvious clues. The next steps toward diagnosing IBS depend on the individual patient’s combination of symptoms.

A diagnosis of irritable bowel syndrome cannot be made until other potential causes of the symptoms have been ruled out. These other causes may include food intolerance or food allergies, gastrointestinal infections, pancreatitis, or an inflammatory bowel disease such as ulcerative colitis, Crohn’s disease, or microscopic colitis. If there is pain in the lower left abdomen, it is especially important to rule out a diverticular disease. It may be necessary to perform an upper endoscopy or colonoscopy, stool tests, and/or a gynecological examination to rule out other conditions.


A key feature of IBS treatment is the fact that each patient has their own unique set of symptoms, which often changes over time. For this reason, there is no single treatment for IBS that is equally suitable for all patients.

Some aspects of IBS treatment are directed at the individual symptoms, whereas others are followed symptom-independent. If a patient has known intolerance to certain foods due to their IBS, avoiding those foods completely can greatly improve their symptoms.

Otherwise, a diet called the low FODMAP diet is a possible option for IBS patients. This diet avoids foods that contain certain types of carbohydrates called “FODMAPs” (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols). These specific carbohydrates pose an additional burden on an already-strained digestive tract, and can lead to diarrhea, gas, and abdominal pain. Therefore, this low FODMAP diet should only be followed for short periods of time under professional supervision.

It may also be helpful to try to alter the composition of the intestinal bacteria (microbiota). This may be possible using synbiotics, which are foods, dietary supplements (prebiotics) and medical products enriched in certain microorganisms (probiotics), that may have beneficial effects on the microbiota.

Psychotherapy, relaxation exercises, or autogenic training may be helpful for patients who suffer from psychological issues resulting from their irritable bowel syndrome.

The medications used to treat IBS are prescribed based on the specific symptoms an individual patient is currently experiencing. For example, if the main symptom is diarrhea, a doctor will prescribe medications that slow the passage of stool through the intestines. In contrast, patients whose main complaint is constipation will be prescribed medications that promote digestion. Experts recommend soluble fibers such as psyllium also known as ispaghula or plantago ovata husks for patients with constipation-predominant IBS. These soluble fibers can bind a lot of water and therefore help to regulate bowel function in constipation-predominant IBS. If soluble fibers do not adequately relieve symptoms of constipation, polyethylene glycol (PEG) products (macrogol) can also be used.

Patients whose main IBS symptom is abdominal pain are usually treated with medications that reduce intestinal cramps (antispasmodic drugs). Herbal remedies such as peppermint oil or caraway oil may also be useful for relieving abdominal pain.

IBS treatments are typically taken for only a short amount of time at first, while the doctor waits to see if the symptoms improve. If they do not, the medication should be stopped after no more than three months and a different treatment strategy should be tested.

Outlook and prognosis

By definition, irritable bowel syndrome is a chronic disease, although it does not usually get worse over time. The symptoms may even gradually get better over the years.