Irritable bowel syndrome
|Irritable bowel syndrome|
|Classification and external resources|
Irritable bowel syndrome (IBS, or spastic colon) is a symptom-based diagnosis characterized by chronic abdominal pain, discomfort, bloating, and alteration of bowel habits. As a functional bowel disorder, IBS has no known organic cause. Diarrhea or constipation may predominate, or they may alternate (classified as IBS-D, IBS-C or IBS-A, respectively). Historically a diagnosis of exclusion, a diagnosis of IBS can now be made on the basis of symptoms alone, in the absence of alarm features such as age of onset greater than 50 years, weight loss, gross hematochezia, systemic signs of infection or colitis, or family history of inflammatory bowel disease. Onset of IBS is more likely to occur after an infection (post-infectious, IBS-PI), a stressful life event, or onset of maturity.
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 themselves as IBS, including coeliac disease, fructose malabsorption, mild infections, parasitic infections like giardiasis, several inflammatory bowel diseases, bile acid malabsorption, functional chronic constipation, small intestinal bacterial overgrowth, 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 has no direct effect on life expectancy. It is, however, a source of chronic pain, fatigue, and other symptoms and contributes to work absenteeism. The high prevalence of IBS and significant effects on quality of life make IBS a disease with a high social cost. It has also been suggested that a proportion of IBS patients may develop depression and are thus more likely to commit suicide. Proposed factors for increased suicide rate in IBS patients include perceived hopelessness and poor quality of services.
IBS can be classified as either diarrhea-predominant (IBS-D), constipation-predominant (IBS-C), or 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).
Signs and symptoms 
The primary symptoms of IBS are abdominal pain or discomfort in association with frequent diarrhea or constipation and a change in bowel habits. There may also be urgency for bowel movements, a feeling of incomplete evacuation (tenesmus), bloating, or abdominal distension. In some cases, the symptoms are relieved by bowel movements. People with IBS, more commonly than others, have gastroesophageal reflux, symptoms relating to the genitourinary system, chronic fatigue syndrome, fibromyalgia, headache, backache and psychiatric symptoms such as depression and anxiety. Some studies indicate that up to 60% of persons with IBS also have a psychological disorder, typically anxiety or depression.
The cause of IBS is unknown; several hypotheses have been proposed. The risk of developing IBS increases sixfold after acute gastrointestinal infection. Postinfection, 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 the study "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. Studies have shown that the nonabsorbed antibiotic rifaximin can provide sustained relief for some IBS patients. While some researchers see this as evidence that IBS is related to an undiscovered agent, others believe IBS patients suffer from overgrowth of intestinal flora and the antibiotics are effective in reducing the overgrowth (known as "small intestinal bacterial overgrowth"). A 2012 study, which connected cultures of bacteria from the small intestine to a significantly increased occurrence of IBS, supports this hypothesis.
Other researchers have focused on an unrecognized protozoal infection as a cause of IBS as certain protozoal infections occur more frequently in 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 though these reports are contested by some physicians. Studies from research hospitals have identified high Blastocystis infection rates in IBS patients, with 38% being reported from London School of Hygiene & Tropical Medicine, 47% reported from the Department of Gastroenterology at Aga Khan University in Pakistan and 18.1% reported from the Institute of Diseases and Public Health at University of Ancona in Italy. Reports from all three groups indicate a Blastocystis prevalence of approximately 7% in non-IBS patients. Researchers have noted that clinical diagnostics fail to identify infection, and Blastocystis may not respond to treatment with common antiprotozoals.
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. A 2002 study reported on a large group of patients with IBS-like symptoms who were found to be infected with Dientamoeba fragilis and experienced resolution of symptoms following 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 defecation 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, and 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 misdiagnosis 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.
Investigations are performed to exclude other conditions:
- Stool microscopy and culture (to exclude infectious conditions)
- Blood tests: Full blood examination, Liver function tests, Erythrocyte sedimentation rate, serological testing for coeliac disease
- Abdominal ultrasound (to exclude gallstones and other biliary tract diseases)
- Endoscopy and biopsies (to exclude peptic ulcer disease, coeliac disease, inflammatory bowel disease, malignancies)
- Hydrogen breath testing (to exclude fructose and lactose malabsorption)
Published research has demonstrated that some poor patient outcomes are due to treatable causes of diarrhea being misdiagnosed as IBS. Common examples include infectious diseases, coeliac disease, Helicobacter pylori, parasites.
Coeliac disease in particular is often misdiagnosed as IBS. The American College of Gastroenterology recommends that all patients with symptoms of IBS be tested for coeliac disease.
Bile acid malabsorption is also often missed in patients with diarrhea-predominant IBS. SeHCAT tests suggest that around 30% of D-IBS have this condition, and most respond to bile acid sequestrants.
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 such 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. Researchers have suggested that IBS and IBD are interrelated diseases, noting that patients with IBD experience IBS-like symptoms when their IBD is in remission. A three-year study found that patients diagnosed with IBS were 16.3 times more likely to be diagnosed with IBD during the study period. Serum markers associated with inflammation have also been found in patients with IBS (see Causes).
- Abdominal surgery: A 2008 study found that IBS patients were 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. A 2005 study reported that IBS patients are 87% more likely to undergo abdominal and pelvic surgery and three times more likely to undergo gallbladder surgery. A study published in Gastroenterology came to similar conclusions, and also noted IBS patients were twice as likely to undergo hysterectomy.
- 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.
Some people with IBS may have food intolerances.
A low FODMAP diet has been shown to reduce symptoms in functional GI disorders such as IBS by 60-80%. This diet restricts various carbohydrates which are poorly absorbed in the small intestine, as well as fructose and lactose, which are similarly poorly absorbed in those with intolerances to them. Reduction of fructose and fructan have been shown to reduce IBS symptoms in a dose-dependent manner in patients with fructose malabsorption and IBS. Many individuals with IBS are lactose intolerant and a trial of a lactose-free diet is often recommended. Alternatively, an over-the-counter remedy containing lactase enzyme can be taken before consuming milk products. Allergy to milk products also causes diarrhea and other symptoms, and this will not be improved by a lactase enzyme supplement. Many who benefit from a low FODMAP diet need not restrict fructose or lactose.
Some IBS patients believe they have some form of dietary intolerance; however, tests attempting to predict food sensitivity in IBS have been disappointing. A small study reported that an IgG antibody test was somewhat 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. However, more research is necessary before IgG testing can be recommended.
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 owing to their heightened visceral sensitivity, and this may lead to abdominal pain, diarrhea, and/or constipation.
There is some evidence that soluble fiber supplementation (e.g., psyllium/ispagula husk) is effective in the general IBS population. It acts as a bulking agent, and for many IBS-D patients, it allows for a more consistent stool. For IBS-C patients, it seems to allow for a softer, moister, more easily passable stool.
Fiber might be beneficial in those who have a predominance of constipation. In patients who have IBS-C, 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. An updated meta-analysis by the same authors also found that soluble fiber reduced symptoms, while insoluble fiber worsened symptoms in some cases. Positive studies have used 10–30 grams per day of psyllium. One study specifically examined the effect of dose and found that 20 grams of ispaghula husk was better than 10 grams and equivalent to 30 grams per day. An uncontrolled study noted increased symptoms with insoluble fibers. It is unclear if these symptoms are truly increased compared with a control group. If the symptoms are increased, it is unclear if these patients were diarrhea predominant (which can be exacerbated by insoluble fiber), or if the increase is temporary before benefit occurs.
Medications may consist of stool softeners and laxatives in constipation-predominant IBS and antidiarrheals (e.g., opiate, opioid, or opioid analogs such as loperamide, codeine, diphenoxylate) in diarrhea-predominant IBS for mild symptoms and stronger opiates such as morphine and oxycodone for severe cases.
Drugs affecting serotonin (5-HT) in the intestines can help reduce symptoms. 5HT3 antagonists such as ondansetron are effective in postinfectious IBS and diarrhoea-dominant IBS due to their blockade of serotonin on 5HT3 receptors in the gut; the reason for their benefit is believed to be that excessive serotonin in the gut is believed to play a role in the pathogenesis of some subtypes of IBS. Benefits may include reduced diarrhoea, reduced abdominal cramps, and improved general well-being. Any nausea present may also respond to 5HT3 antagonists owing to their antiemetic properties. Serotonin stimulates the gut motility and so agonists can help constipation-predominate irritable bowel, while antagonists can help diarrhea-predominant irritable bowel. Selective serotonin re-uptake inhibitors, SSRIs, frequently prescribed for panic and/or anxiety disorder and depression, affect serotonin in the gut as well as the brain. The bowels are highly dependent on serotonin for neural communication. "Selective serotonin re-uptake inhibitor antidepressants seem to promote global well-being in some patients with irritable bowel syndrome and, possibly, some improvement in abdominal pain and bowel symptoms, but this effect appears to be independent of improved depression. Further research is required."
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.
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 seven patients are treated with antispasmodics, one patient will benefit. Antispasmodics can be divided in two groups: neurotropics and musculotropics.
- Neurotropics — for example, phenobarbitals such as Donnatal or atropine — act at the nerve fibre of the parasympathicus but also affect other nerves, causing side effects in many patients.
- 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. However, there is less robust evidence as to the effectiveness of other antidepressant classes such as 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 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.
- 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 and randomized controlled trials 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
There is conflicting evidence about the benefit of antidepressants in IBS. Some meta-analyses have found a benefit while others have not. A meta-analysis of randomized controlled trials of mainly TCAs found three patients have to be treated with TCAs for one patient to improve. A separate randomized controlled trial found that TCAs are best for patients with diarrhea-predominant IBS.
Recent studies have suggested that rifaximin can be used as an effective treatment for abdominal bloating and flatulence, giving more credibility to the potential role of bacterial overgrowth in some patients with IBS.
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 potential risk of tolerance, physical dependence, and addiction but can be the only relief for some diarrhea-predominant cases when other treatment has been ineffective.
- SIBO Therapy
The mind-body or brain-gut interactions has been proposed for irritable bowel syndrome and is gaining increasing research attention. For some patients, psychological therapies may help with symptoms. Cognitive behavioural therapy and hypnosis have been found to be the most beneficial. Hypnosis can improve mental well-being, and cognitive behavioural therapy can provide psychological coping strategies for dealing with distressing symptoms as well as help suppress thoughts and behaviours that increase the symptoms of irritable bowel syndrome. Cognitive behavioral therapy has been found to improve symptoms in a number of studies. Relaxation therapy has also been found to be helpful.
A questionnaire in 2006 designed to identify patients’ perceptions about IBS, their preferences on the type of information they need, and 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%).
Stress relief 
Reducing stress may reduce the frequency and severity of IBS symptoms. Techniques that may be helpful include:
- Relaxation techniques such as meditation
- Physical activities such as yoga or tai chi
- Regular exercise such as swimming, walking or running
Many patients find that exercise helps with IBS. At least 30 minutes of strenuous exercise 5 times a week is recommended.
Alternative medicine 
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. A number of probiotics have been found to be effective including: Lactobacillus plantarum and Bifidobacteria infantis; 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 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.
- Kiwifruit IBS/C
- Commiphora mukul
- Plantago ovata
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 may be effective for some with irritable bowel syndrome, especially poses which exercise the lower abdomen.
Acupuncture may be worth a trial in select patients, but the evidence base for effectiveness is weak. A meta-analysis by the Cochrane Collaboration found no benefits of acupuncture relative to placebo for IBS symptom severity or IBS-related quality of life.
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:
|Percentage of population reporting symptoms of IBS in various studies from various geographic areas|
|Japan||10%||Quigley, 2006||Study measured prevalence of GI abdominal pain/cramping|
|Prevalence increased substantially 1970–2004|
|United States||14.1%||Hungin, 2005||Most undiagnosed|
|United States||15%||Boivin, 2001||Estimate|
|Pakistan||14%||Jafri, 2007||Much more common in 16–30 age range. Of IBS patients, 56% male, 44% female|
|Pakistan||34%||Jafri, 2005||College students|
|Mexico City||35%||Schmulson, 2006||n=324. Also measured functional diarrhea and functional vomiting. High rates attributed to "stress of living in a populated city."|
|Brazil||43%||Quigley, 2006||Study measured prevalence of GI abdominal pain/cramping|
|Mexico||46%||Quigley, 2006||Study 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.
Sex and gender differences 
Women are approximately two to three times more likely to be diagnosed with IBS and four to five times more likely to seek specialty care for IBS than are men. These differences likely reflect a combination of both biological (sex) and social (gender) factors. Studies of female patients with IBS show that symptom severity often fluctuates with the menstrual cycle, suggesting that hormonal differences may play a role. Endorsement of gender-related traits has been associated with quality of life and psychological adjustment in IBS. Greater reductions in quality of life may make women with IBS more likely to seek treatment for their symptoms. More generally, gender differences in healthcare-seeking may also play a role. Gender differences in trait anxiety may contribute to lower pain thresholds in women, putting them at greater risk for a number of chronic pain disorders. Finally, sexual trauma is a major risk factor for IBS, with as many as 33% of all patients reporting such abuse. Because women are at higher risk of sexual abuse than men, gender-related risk of abuse may contribute to the higher prevalence of IBS in women.
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 examples and perspective in this section may not represent a worldwide view of the subject. (July 2011)|
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. A study by a managed care company comparing medical costs of IBS patients to non-IBS controls identified a 49% annual increase in medical costs associated with a diagnosis of IBS. A 2007 study from a managed care organization found that IBS patients incurred average annual direct costs of $5,049 and $406 in out-of-pocket expenses. A study of workers with IBS found that they reported a 34.6% loss in productivity, corresponding to 13.8 hours lost per 40 hour week. A study of employer-related health costs from a Fortune 100 company conducted with data from the 1990s found IBS patients incurred US $4527 in claims costs vs. $3276 for controls. A study on Medicaid costs conducted in 2003 by the University of Georgia's College of Pharmacy and Novartis found IBS was associated in an increase of $962 in Medicaid costs in California, and $2191 in North Carolina. IBS patients had higher costs for physician visits, outpatients visits, and prescription drugs. The study suggested the costs associated with IBS were comparable to those found in asthma patients.
Gibson and Shepherd state a diet restricted in fermentable oligo- di- and mono-saccharides and polyols (FODMAPs) 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 FODMAPs 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.
See also 
- Chronic functional abdominal pain
- Food intolerance
- Functional constipation
- Functional dyspepsia
- Fructose malabsorption
- Lactose intolerance
- Bile acid malabsorption
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- UNC Center for Functional GI & Motility Disorders
- Irritable bowel syndrome at the Open Directory Project