Irritable bowel syndrome

Irritable Bowel Syndrome (IBS)

Irritable Bowel Syndrome (IBS)

Irritable bowel syndrome is a functional gastrointestinal (GI) disorder, meaning symptoms are caused by changes in how the GI tract works. People with a functional GI disorder have frequent symptoms; however, the GI tract does not become damaged. IBS is a group of symptoms that occur together, not a disease. In the past, IBS was called colitis, mucous colitis, spastic colon, nervous colon, and spastic bowel. The name was changed to reflect the understanding that the disorder has both physical and mental causes and is not a product of a person’s imagination.

IBS is diagnosed when a person has had abdominal pain or discomfort at least three times a month for the last 3 months without other disease or injury that could explain the pain. The pain or discomfort of IBS may occur with a change in stool frequency or consistency or be relieved by a bowel movement.

Irritable bowel syndrome

IBS is often classified into four subtypes based on a person’s usual stool consistency. These subtypes are important because they affect the types of treatment that are most likely to improve the person’s symptoms. The four subtypes of IBS are

  • IBS with constipation (IBS-C)

→ Hard or lumpy stools at least 25 percent of the time

→ Loose or watery stools less than 25 percent of the time

  • IBS with diarrhea (IBS-D)

→ Loose or watery stools at least 25 percent of the time

→ Hard or lumpy stools less than 25 percent of the time

  • Mixed IBS (IBS-M)

→ Hard or lumpy stools at least 25 percent of the time

→ Loose or watery stools at least 25 percent of the time

  • Unsubtyped IBS (IBS-U)

→ Hard or lumpy stools less than 25 percent of the time

→ Loose or watery stools less than 25 percent of the time

It must be remembered, however, that:

  • Patients commonly transition between these subtypes.
  • The symptoms of diarrhea and constipation are commonly misinterpreted in IBS patients. Thus, many IBS patients who complain of “diarrhea” are referring to the frequent passage of formed stools and, in the same patient population, “constipation” may refer to any one of a variety of complaints associated with the attempted act of defecation and not simply to infrequent bowel movements.
  • In addition, bowel habit must be evaluated without using antidiarrheal or laxatives.

What Causes IBS?

Researchers have yet to discover any specific cause for IBS. One theory is that people who suffer from IBS have a colon, or large intestine, that is particularly sensitive and reactive to certain foods and stress. The immune system, which fights infection, may also be involved.

  • Normal motility, or movement, may not be present in the colon of a person who has IBS. It can be spasmodic or can even stop working temporarily. Spasms are sudden strong muscle contractions that come and go.
  • The lining of the colon called the epithelium, which is affected by the immune and nervous systems, regulates the flow of fluids in and out of the colon. In IBS, the epithelium appears to work properly. However, when the contents inside the colon move too quickly, the colon loses its ability to absorb fluids. The result is too much fluid in the stool. In other people, the movement inside the colon is too slow, which causes extra fluid to be absorbed. As a result, a person develops constipation.
  • A person’s colon may respond strongly to stimuli such as certain foods or stress that would not bother most people.
  • Recent research has reported that serotonin is linked with normal gastrointestinal (GI) functioning. Serotonin is a neurotransmitter, or chemical, that delivers messages from one part of your body to another. Ninety-five percent of the serotonin in your body is located in the GI tract, and the other 5 percent is found in the brain. Cells that line the inside of the bowel work as transporters and carry the serotonin out of the GI tract. People with IBS, however, have diminished receptor activity, causing abnormal levels of serotonin to exist in the GI tract. As a result, they experience problems with bowel movement, motility, and sensation—having more sensitive pain receptors in their GI tract.
  • Researchers have reported that IBS may be caused by a bacterial infection in the gastrointestinal tract. Studies show that people who have had gastroenteritis sometimes develop IBS, otherwise called post-infectious IBS.
  • Researchers have also found very mild celiac disease in some people with symptoms similar to IBS. People with celiac disease cannot digest gluten, a substance found in wheat, rye, and barley. People with celiac disease cannot eat these foods without becoming very sick because their immune system responds by damaging the small intestine. A blood test can determine whether celiac disease may be present.
  • Whether IBS has a genetic cause, meaning it runs in families, is unclear. Studies have shown IBS is more common in people with family members who have a history of GI problems. However, the cause could be environmental or the result of heightened awareness of GI symptoms.
  • Food sensitivity. Many people with IBS report that symptoms are triggered by foods rich in carbohydrates, spicy or fatty foods, coffee, and alcohol. However, people with food sensitivity typically do not have clinical signs of food allergy. Researchers have proposed that symptoms may result from poor absorption of sugars or bile acids, which help break down fats and get rid of wastes in the body
  • Mental Health Problems. Mental health, or psychological, problems such as panic disorder, anxiety, depression, and post-traumatic stress disorder are common in people with IBS. The link between these disorders and development of IBS is unclear. GI disorders, including IBS, are often found in people who have reported past physical or sexual abuse. Researchers believe people who have been abused tend to express psychological stress through physical symptoms.

Other factors that may trigger IBS symptoms:

  • Low fibre diet
  • High fat diet
  • Food intolerances
  • Increased use of antibiotics
  • Busy lifestyle/stress
  • Stomach surgery
  • Emotional upset
  • Combination of the above factors

What are the symptoms?

The hallmark of IBS is abdominal pain or discomfort associated with either a change in bowel habits or disordered defecation. The pain or discomfort associated with IBS is often poorly localized and may be migratory and variable. It may occur after a meal, during stress or at the time of menses. In addition to pain and discomfort, altered bowel habits are common, including diarrhea, constipation, and diarrhea alternating with constipation. Patients also complain of bloating or abdominal distension, mucous in the stool, urgency, and a feeling of incomplete evacuation. Some patients describe frequent episodes, whereas others describe long symptom-free periods. Patients with irritable bowel frequently report symptoms of other functional gastrointestinal disorders as well, including chest pain, heartburn, nausea or dyspepsia, difficulty swallowing, or a sensation of a lump in the throat or closing of the throat

Symptoms may vary from barely noticeable to debilitating, at times within the same patient. In some patients, stress or life crises may be associated with the onset of symptoms, which may then disappear when the stress dissipates. Other patients seem to have random IBS episodes with spontaneous remissions. Still others describe long periods of symptoms and long symptom-free periods.

In general, the symptoms of IBS wax and wane throughout life, but the majority of patients seen by physicians is 20–50 years old. In approximately 50% of patients, symptoms begin before age 35. The disorder is also recognized in children, generally appearing in early adolescence. Many patients can trace the onset of symptoms back to childhood. The prevalence of IBS is slightly lower in the elderly, and in this patient population organic disorders must be excluded.

Symptoms unrelated to the intestine (extra intestinal symptoms) are common in patients with IBS. These may include headache, sleep disturbances, post-traumatic stress disorder, temporomandibular joint disorder, sicca syndrome, back/pelvic pain, myalgias, back pain, and chronic pelvic pain (Figure 8). Fibromyalgia and interstitial cystitis are also frequently encountered in patients with IBS. In fact, Fibromyalgia occurs in up to 33% of patients with IBS and almost half of patients with fibromyalgia also have IBS

How is IBS Diagnosed?

If you think you have IBS, seeing your doctor is the first step. IBS is generally diagnosed on the basis of a complete medical history that includes a careful description of symptoms and a physical examination.

There is no specific test for IBS, although diagnostic tests may be performed to rule out other problems. These tests may include stool sample testing, blood tests, and x rays. Typically, a doctor will perform a sigmoidoscopy, or colonoscopy, which allows the doctor to look inside the colon. This is done by inserting a small, flexible tube with a camera on the end of it through the anus. The camera then transfers the images of your colon onto a large screen for the doctor to see well.

If your test results are negative, the doctor may diagnose IBS based on your symptoms, including how often you have had abdominal pain or discomfort during the past year, when the pain starts and stops in relation to bowel function, and how your bowel frequency and stool consistency have changed.  Many  doctors  refer  to  a  list  of  specific  symptoms  that  must  be  present  to  make  a diagnosis of IBS.

How is IBS treated?

Though IBS does not have a cure, the symptoms can be treated with a combination of

  • Changes in eating, diet, and nutrition
  • Medications
  • Probiotics
  • Therapies for mental health problems

Eating, Diet, and Nutrition

Large meals can cause cramping and diarrhea, so eating smaller meals more often, or eating smaller portions, may help IBS symptoms. Eating meals that are low in fat and high in carbohydrates, such as pasta, rice, whole-grain breads and cereals, fruits, and vegetables, may help.

Certain foods and drinks may cause IBS symptoms in some people, such as

  • Foods high in fat
  • Some milk products
  • Drinks with alcohol or caffeine
  • Drinks with large amounts of artificial sweeteners, which are used in place of sugar
  • Beans, cabbage, and other foods that may cause gas

People with IBS may want to limit or avoid these foods. Keeping a food diary is a good way to track which foods cause symptoms so they can be excluded from or reduced in the diet.

Dietary fiber may improve constipation symptoms in people with IBS, although it may not help with reducing pain. Fiber softens stool so it moves smoothly through the colon. Adults are advised to consume 21 to 38 grams of fiber a day. Fiber may cause gas and trigger symptoms in some people with IBS. Increasing fiber intake slowly, by 2 to 3 grams a day, may help reduce the risk of increased gas and bloating.

Medications

A health care provider will select medications based on a person’s symptoms.

  • Fiber supplements may be recommended to relieve constipation when increasing dietary fiber is ineffective.
  • Laxatives may help constipation. Laxatives work in different ways, and a health care provider can provide information about which type is best for each person.
  • Loperamide is an antidiarrheal that has been found to reduce diarrhea in people with IBS, though it does not reduce pain, bloating, or other symptoms. Loperamide reduces stool frequency and improves stool consistency by slowing the movement of stool through the colon.
  • Antispasmodics, such as hyoscine, cimetropium, and pinaverium, help to control colon muscle spasms and reduce abdominal pain.
  • Antidepressants, such as low doses of tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs), can help relieve IBS symptoms, including abdominal pain. In theory, TCAs should be better for people with IBS-D and SSRIs should be better for people with IBS-C due to the effect on colon transit, although this theory has not been confirmed in clinical studies. TCAs work in people with IBS by reducing sensitivity to pain in the GI tract as well as normalizing GI motility and secretion.
  • Lubiprostone (Amitiza) is prescribed for people who have IBS-C. The medication has been found to improve abdominal pain or discomfort, stool consistency, straining, and constipation severity.
  • Linaclotide (Linzess) is also prescribed for people who have IBS-C. Linzess has been found to relieve abdominal pain and increase the frequency of bowel movements.

The antibiotic rifaximin can reduce abdominal bloating by treating small intestinal bacterial overgrowth; however, scientists are still debating the use of antibiotics to treat IBS and more research is needed.

Probiotics

Probiotics are live microorganisms, usually bacteria, that are similar to microorganisms normally found in the GI tract. Studies have found that when taken in large enough amounts, probiotics, specifically Bifidobacteria and certain probiotic combinations, improve symptoms of IBS. However, more research is needed. Probiotics can be found in dietary supplements, such as capsules, tablets, and powders, and in some foods, such as yogurt. A health care provider can give information about the right kind and amount of probiotics to take to improve IBS symptoms.

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