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March 26, 2016
Table of Contents

1 Introduction
IBS Research

Wikipedia

 

Irritable bowel syndrome ( IBS or spastic colon ) is a diagnosis of exclusion. It is a functional bowel disorder characterized by chronic abdominal pain, discomfort, bloating, and alteration of bowel habits in the absence of any detectable organic cause. In some cases, the symptoms are relieved by bowel movements. Diarrhea or constipation may predominate, or they may alternate (classified as IBS-D , IBS-C or IBS-A , respectively). IBS may begin after an infection (post-infectious, IBS-PI ), a stressful life event, or onset of maturity without any other medical indicators.

Although there is no cure for IBS, there are treatments that attempt to relieve symptoms, including dietary adjustments, medication and psychological interventions . Patient education and a good doctor-patient relationship are also important.

Several conditions may present as IBS including celiac disease, fructose malabsorption, mild infections, parasitic infections like giardiasis, several inflammatory bowel diseases, functional chronic constipation , and chronic functional abdominal pain. In IBS, routine clinical tests yield no abnormalities, although the bowels may be more sensitive to certain stimuli, such as balloon insufflation testing. The exact cause of IBS is unknown . The most common theory is that IBS is a disorder of the interaction between the brain and the gastrointestinal tract, although there may also be abnormalities in the gut flora or the immune system.

IBS does not lead to more serious conditions in most patients. However, it is a source of chronic pain, fatigue, and other symptoms, and it increases a patient's medical costs, and contributes to work absenteeism. Researchers have reported that the high prevalence of IBS, in conjunction with increased costs, produces a disease with a high societal cost. It is also regarded as a chronic illness and can dramatically affect the quality of a sufferer's life.




IBS can be classified as either diarrhea-predominant ( IBS-D ), constipation-predominant ( IBS-C ) or IBS with alternating stool pattern ( IBS-A or pain-predominant). In some individuals, IBS may have an acute onset and develop after an infectious illness characterized by two or more of the following: fever, vomiting, diarrhea, or positive stool culture. This post-infective syndrome has consequently been termed "post-infectious IBS" ( IBS-PI ).




The primary symptoms of IBS are abdominal pain or discomfort in association with frequent diarrhea or constipation, a change in bowel habits. Some studies indicate that up to 60% of persons with IBS also have a psychological disorder, typically anxiety or depressions.




The cause of IBS is unknown, but several hypotheses have been proposed. The risk of developing IBS increases sixfold after acute gastrointestinal infection. Post-infection, further risk factors are young age, prolonged fever, anxiety, and depression. Publications suggesting the role of brain-gut "axis" appeared in the 1990s, such as a study entitled Brain-gut response to stress and cholinergic stimulation in IBS published in the Journal of Clinical Gastroenterology in 1993. A 1997 study published in Gut magazine suggested that IBS was associated with a "derailing of the brain-gut axis." Psychological factors may be important in the etiology of IBS .

Active infections

There is research to support IBS being caused by an as-yet undiscovered active infection. Most recently, a study found that the antibiotic Rifaximin provides sustained relief for IBS patients. Two of the protozoa investigated have a high prevalence in industrialized countries and infect the bowel, but little is known about them as they are recently emerged pathogens.

Blastocystis is a single-cell organism that has been reported to produce symptoms of abdominal pain, constipation and diarrhea in patients

Dientamoeba fragilis is a single-cell organism that produces abdominal pain and diarrhea. Studies have reported a high incidence of infection in developed countries, and symptoms of patients resolve following antibiotic treatment. Researchers have noted that methods used clinically may fail to detect some Dientamoeba fragilis infections. It is also found in people without IBS.




There is no specific laboratory or imaging test that can be performed to diagnose irritable bowel syndrome. Diagnosis of IBS involves excluding conditions that produce IBS-like symptoms, and then following a procedure to categorize the patient's symptoms. Ruling out parasitic infections, lactose intolerance, small intestinal bacterial overgrowth and celiac disease is recommended for all patients before a diagnosis of irritable bowel syndrome is made. In patients over 50 years old it is recommended that they undergo a screening colonoscopy.

Differential diagnosis

Colon cancer, inflammatory bowel disease, thyroid disorders and giardiasis can all feature abnormal defication and abdominal pain. Less common causes of this symptom profile are carcinoid syndrome, microscopic colitis, bacterial overgrowth, and eosinophilic gastroenteritis. IBS is, however, such a common presentation and testing for these conditions would yield such low numbers of positive results that it is considered difficult to justify the expense.

Because there are many causes of diarrhea that give IBS-like symptoms, the American Gastroenterological Association published a set of guidelines for tests to be performed to rule out other causes for these symptoms. These include gastrointestinal infections, lactose intolerance, and coeliac disease. Research has suggested that these guidelines are not always followed. Once other causes have been excluded, the diagnosis of IBS is performed using a diagnostic algorithm. Well-known algorithms include the Manning Criteria, the obsolete Rome I and II criteria , the Kruis Criteria, and studies have compared their reliability. The more recent Rome III Process was published in 2006. Physicians may choose to use one of these guidelines, or may simply choose to rely on their own anecdotal experience with past patients. The algorithm may include additional tests to guard against mis-diagnosis of other diseases as IBS. Such "red flag" symptoms may include weight loss, gastrointestinal bleeding, anemia, or nocturnal symptoms. However, researchers have noted that red flag conditions may not always contribute to accuracy in diagnosis — for instance, as many as 31% of IBS patients have blood in their stool many possibly from hemorrhoidal bleeding.

The diagnostic algorithm identifies a name that can be applied to the patient's condition based on the combination of the patient's symptoms of diarrhea, abdominal pain, and constipation. For example, the statement "50% of returning travelers had developed functional diarrhea while 25% had developed IBS" would mean that half the travelers had diarrhea while a quarter had diarrhea with abdominal pain. While some researchers believe this categorization system will help physicians understand IBS, others have questioned the value of the system and suggested that all IBS patients have the same underlying disease but with different symptoms.

On this line is a recent study, which showed that constipation and/or diarrhea seems to be different manifestations of the same underlying condition, that is a build-up of fecal retention reservoirs in the colon. Abdominal X-rays were analyzed for colon transit time and fecal distribution, which correlated significantly with bloating and abdominal pain. Thus a group of patients were identified with an increased fecal loading compared to controls, but having a colon transit time equal or less to the controls. This suggest that defecation patterns do not reflect the amount of feces in the colon and is called hidden constipation . This phenomenon may be linked to bacterial overgrowth.

Misdiagnosis

Published research has demonstrated that some poor patient outcomes are due to treatable causes of diarrhea being mis-diagnosed as IBS. Common examples include infectious diseases, coeliac disease, Helicobacter pylori, parasites.

Celiac disease in particular is often misdiagnosed as IBS. The American College of Gastroenterology recommends that all patients with symptoms of IBS be tested for celiac disease. Chronic use of certain sedative- hypnotic drugs especially the benzodiazepines may cause irritable bowel like symptoms that can lead to a misdiagnosis of irritable bowel syndrome.

Comorbidities

Researchers have identified several medical conditions, or comorbidities, which appear with greater frequency in patients diagnosed with IBS.

Headache, Fibromyalgia, Chronic fatigue syndrome and Depression : A study of 97,593 individuals with IBS identified comorbidities as headache, fibromyalgia, and depression. A systematic review found that IBS occurs in 51% of chronic fatigue syndrome patients and 49% of fibromyalgia patients, and psychiatric disorders were found to occur in 94% of IBS patients.

Inflammatory bowel disease (IBD) : Some researchers have suggested that IBS is a type of low-grade inflammatory bowel disease. Serum markers associated with inflammation have also been found in patients with IBS (see Causes).

Abdominal surgery : A recent (2008) study found that IBS patients are at increased risk of having unnecessary cholecystectomy (gall bladder removal surgery) not due to an increased risk of gallstones, but rather to abdominal pain, awareness of having gallstones, and inappropriate surgical indications.

Endometriosis: One study reported a statistically significant link between migraine headaches, IBS, and endometriosis.

Other chronic disorders : Interstitial cystitis may be associated with other chronic pain syndromes, such as irritable bowel syndrome and fibromyalgia. The connection between these syndromes is unknown.




A number of treatments have been found to be better than placebo, including fiber, antispasmodics, and peppermint oil.

Diet

Some people with IBS are likely to have food intolerances. In 2007 the evidence base was not strong enough to recommend restrictive diets.

Many different dietary modifications have been attempted to improve the symptoms of IBS. Some are effective in certain sub-populations. As lactose intolerance and IBS have such similar symptoms a trial of a lactose free diet is often recommended. A diet restricting fructose and fructan intake has been shown to successfully treat the symptoms in a dose-dependant manner in patients with fructose malabsorption and IBS.

While many IBS patients believe they have some form of dietary intolerance, tests attempting to predict food sensitivity in IBS have been disappointing. One study reported that an IgG antibody test was effective in determining food sensitivity in IBS patients, with patients on the elimination diet experiencing 10% greater symptom reduction than those on a sham diet.

There is no evidence that digestion of food or absorption of nutrients is problematic for those with IBS at rates different from those without IBS. However, the very act of eating or drinking can provoke an overreaction of the gastrocolic response in some patients with IBS due to their heightened visceral sensitivity, and this may lead to abdominal pain, diarrhea, and/or constipation.

Fiber

There is convincing evidence that soluble fiber supplementation (e.g., psyllium) is effective in the general IBS population. Insoluble fiber (e.g., bran) has not been found to be effective for IBS.

Fiber might be beneficial in those who have a predominance of constipation. In patients who have constipation predominant irritable bowel, soluble fiber at doses of 20 grams per day can reduce overall symptoms but will not reduce pain. The research supporting dietary fiber contains conflicting, small studies that are complicated by the heterogeneity of types of fiber and doses used.

One meta-analysis found that only soluble fiber improved global symptoms of irritable bowel, but neither type of fiber reduced pain. However, an updated meta-analysis by the same authors found that soluble fiber reduced symptoms. An uncontrolled study noted increased symptoms with insoluble fibers.), or if the increase is temporary before benefit occurs.

Medication

Medications may consist of stool softeners and laxatives in constipation-predominant IBS, and antidiarrheals (e.g., opiate, opioid, or opioid analog s such as loperamide, codeine, diphenoxylate) in diarrhea-predominant IBS for mild symptoms.

Drugs affecting serotonin (5-HT) in the intestines can help reduce symptoms. Serotonin stimulates the gut motility and so agonists can help constipation-predominate irritable bowel, while antagonists can help diarrhea-predominant irritable bowel.

Laxatives

For patients who do not adequately respond to dietary fiber, osmotic laxatives such as polyethylene glycol, sorbitol, and lactulose can help avoid "cathartic colon," which has been associated with stimulant laxatives. Among the osmotic laxatives, 17–26 grams/day of polyethylene glycol (PEG) has been well studied.

Lubiprostone (Amitiza), is a gastrointestinal agent used for the treatment of idiopathic chronic constipation and constipation-predominant IBS. It is well-tolerated in adults, including elderly patients. As of July 20, 2006, Lubiprostone had not been studied in pediatric patients. Lubiprostone is a bicyclic fatty acid ( prostaglandin E1 derivative) that acts by specifically activating ClC-2 chloride channels on the apical aspect of gastrointestinal epithelial cells, producing a chloride-rich fluid secretion. These secretions soften the stool, increase motility, and promote spontaneous bowel movements (SBM). Unlike many laxative products, Lubiprostone does not show signs of tolerance, dependency, or altered serum electrolyte concentration.

Antispasmodics

The use of antispasmodic drugs (e.g., anticholinergics such as hyoscyamine or dicyclomine) may help patients, especially those with cramps or diarrhea. A meta-analysis by the Cochrane Collaboration concludes that if 6 patients are treated with antispasmodics, 1 patient will benefit. Antispasmodics can be divided in two groups: neurotropics and musculotropics.

  • Neurotropics, such as atropine, act at the nerve fibre of the parasympathicus but also affect other nerves and have side effects.

  • Musculotropics such as mebeverine act directly at the smooth muscle of the gastrointestinal tract, relieving spasm without affecting normal gut motility. Since this action is not mediated by the autonomic nervous system, the usual anticholinergic side effects are absent.

Tricyclic antidepressants

There is strong evidence that low doses of tricyclic antidepressants can be effective for irritable bowel syndrome. There is little evidence of effectiveness of other antidepressant classes such as the SSRIs.

Serotonin agonists

  • Tegaserod (Zelnorm), a selective 5-HT4 agonist for IBS-C, is available for relieving IBS constipation in women and chronic idiopathic constipation in men and women. On March 30, 2007, the Food and Drug Administration (FDA) requested that Novartis Pharmaceuticals voluntarily discontinue marketing of tegaserod based on the recently identified finding of an increased risk of serious cardiovascular adverse events (heart problems) associated with use of the drug. Novartis agreed to voluntarily suspend marketing of the drug in the United States and in many other countries. On July 27, 2007 the Food and Drug Administration (FDA) approved a limited treatment IND program for tegaserod in the USA to allow restricted access to the medication for patients in need if no comparable alternative drug or therapy is available to treat the disease. The USA FDA had issued two previous warnings about the serious consequences of tegaserod. In 2005, tegaserod was rejected as an IBS medication by the European Union. Tegaserod, marketed as Zelnorm in the United States, was the only agent approved to treat the multiple symptoms of IBS (in women only), including constipation, abdominal pain and bloating. A meta-analysis by the Cochrane Collaboration concludes that if 17 patients are treated with typical doses of tegaserod, 1 patient will benefit.

  • Selective serotonin reuptake inhibitor anti-depressants (SSRIs), because of their serotonergic effect, would seem to help IBS, especially patients who are constipation predominant. Initial crossover studies support this role.

Serotonin antagonists

Alosetron, a selective 5-HT3 antagonist for IBS-D and cilansetron (also a selective 5-HT3 antagonist) were trialed for irritable bowel syndrome. Due to severe adverse effects, namely ischemic colitis and severe constipation, they are not available or recommended for irritable bowel syndrome.

Other agents

Magnesium aluminum silicates and alverine citrate drugs can be effective for irritable bowel syndrome.

There is conflicting evidence about the benefit of antidepressants in IBS. Some meta-analysis have found a benefit while others have not. A meta-analysis of randomized controlled trials of mainly TCA s found 3 patients have to be treated with TCAs for one patient to improve.

Recent studies have suggested that rifaximin can be used as an effective treatment for abdominal bloating and flatulence,

Domperidone, a dopamine receptor blocker and a parasympathomimetic, has been shown to reduce bloating and abdominal pain as a result of an accelerated colon transit time and reduced faecal load, that is a relief from hidden constipation ; defecation was similarly improved.

The use of opioids is controversial due to the lack of evidence supporting their benefit and the potential risk of tolerance, physical dependence and addiction .

Psychotherapy

The mind-body or brain-gut interactions has been proposed for irritable bowel syndrome and is gaining increasing research attention.

A questionnaire in 2006 designed to identify patients??? perceptions about IBS, their preferences on the type of information they need, as well as educational media and expectations from health care providers, revealed misperceptions about IBS developing into other conditions, including colitis, malnutrition, and cancer.

The survey found IBS patients were most interested in learning about foods to avoid (60%), causes of IBS (55%), medications (58%), coping strategies (56%), and psychological factors related to IBS (55%). The respondents indicated that they wanted their physicians to be available via phone or e-mail following a visit (80%), have the ability to listen (80%), and provide hope (73%) and support (63%).

Alternative medicine

Due to often unsatisfactory results from medical treatments for IBS up to 50 percent of people turn to complementary alternative medicine.

Probiotics

Probiotics can be beneficial in the treatment of IBS, taking 10 billion to 100 billion beneficial bacteria per day is recommended for beneficial results. However, further research is needed on individual strains of beneficial bacteria for more refined recommendations. however, one review found that only Bifidobacteria infantis showed efficacy. Some yogurt is made using probiotics that may help ease symptoms of irritable bowel syndrome.

Herbal remedies

  • Peppermint oil: Enteric coated peppermint oil capsules have been suggested for IBS symptoms in adults and children. There is good evidence of a beneficial effect of these capsules and it is recommended that peppermint be trialed in all irritable bowel syndrome patients. Safety during pregnancy has not been established however and caution is required not to chew or break the enteric coating otherwise gastroesophageal reflux may occur as a result of lower esophageal sphincter relaxation. Occasionally nausea and perianal burning occur as side effects.

  • Iberogast: The multi-herbal extract Iberogast was found to be significantly superior to placebo via both an abdominal pain scale and an IBS symptom score after four weeks of treatment.

There is only limited evidence for the effectiveness of other herbal remedies for irritable bowel syndrome. As with all herbs it is wise to be aware of possible drug interactions and adverse effects.

Yoga

Yoga may be effective for some sufferers of irritable bowel syndrome.

Acupuncture

Acupuncture may be worth a trial in select patients, but the evidence base for effectiveness is weak.




Studies have reported that the prevalence of IBS varies by country and by age range examined. The bar graph at right shows the percentage of the population reporting symptoms of IBS in studies from various geographic regions (see table below for references).

The following table contains a list of studies performed in different countries that measured the prevalence of IBS and IBS-like symptoms:10.5%Wilson, 2004|-
Percentage of population reporting symptoms of IBS in various studies from various geographic areas
Country Prevalence Author/Year Notes
Canada6%Boivin, 2001-Japan10%Quigley, 2006Study measured prevalence of GI abdominal pain/cramping
United Kingdom 8.2%Ehlin, 2003
Prevalence increased substantially 1970-2004
United States14.1%Hungin, 2005Most undiagnosed
United States15%Boivin, 2001Estimate
Pakistan14%Jafri, 2007Much more common in 16-30 age range. Of IBS patients, 56% male, 44% female
Pakistan34%Jafri, 2005College students
Mexico City35%Schmulson, 2006n=324. Also measured functional diarrhea and functional vomiting. High rates attributed to "stress of living in a populated city."
Brazil43%Quigley, 2006Study measured prevalence of GI abdominal pain/cramping
Mexico46%Quigley, 2006Study measured prevalence of GI abdominal pain/cramping

A study of United States residents returning from international travel found a high rate of IBS and persistent diarrhea that developed during travel and persisted upon return. The study examined 83 subjects in Utah, most of whom were returning missionaries. Of the 68 who completed the gastrointestinal questionnaire, 27 reported persistent diarrhea that developed while traveling, and 10 reported persistent IBS that developed while traveling.




One of the first references to the concept of an "irritable bowel" appeared in the Rocky Mountain Medical Journal in 1950. The term was used to categorize patients who developed symptoms of diarrhea, abdominal pain, constipation, but where no well-recognized infective cause could be found. Early theories suggested that the irritable bowel was caused by a psychosomatic or mental disorder.




The aggregate cost of irritable bowel syndrome in the United States has been estimated at $1.7-$10 billion in direct medical costs, with an additional $20 billion in indirect costs, for a total of $21.7-$30 billion.




Gibson and Shepherd state a low FODMAP diet now has an evidence base sufficiently strong to recommend its widespread application in conditions such as IBS and IBD . They also state the restriction of fermentable oligo- , di- and monosaccharides and polyols globally, rather than individually, controls the symptoms of functional gut disorders (e.g., IBS), and the majority of IBD patients respond just as well. It is more successful than restricting only fructose and fructans, which are also FODMAPs, as is recommended for those with fructose malabsorption. Longer term compliance with the diet was high.

A randomised controlled trial on IBS patients found relaxing an IgG-mediated food intolerance diet led to a 24% greater deterioration in symptoms compared to those on the elimination diet and concluded food elimination based on IgG antibodies may be effective in reducing IBS symptoms and is worthy of further biomedical research.

The National Institutes of Health provides a searchable database for grant awards since 1974 on its CRISP database, and provides dollar amounts for recent awards on its Intramural Grant Award Page .

In 2006, the NIH awarded approximately 56 grants related to IBS, totalling approximately $18.7 million.




  • Functional dyspepsia

  • Chronic functional abdominal pain

  • Functional constipation

  • Food intolerance

  • Fructose malabsorption

  • Hypersensitivity





  • UNC Center for Functional GI & Motility Disorders



This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "IBS Research".


Last Modified:   2010-11-25


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