Irritable bowel syndrome

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In Gastroenterology, irritable bowel syndrome (IBS) or spastic colon is a functional bowel disorder characterized by abdominal pain and changes in bowel habits which are not associated with any abnormalities seen on routine clinical testing. It is fairly common and makes up 20-50% of visits to gastroenterologists. Lower abdominal pain, and bloating associated with alteration of bowel habits and abdominal discomfort relieved with defecation are the most frequent symptoms. The abdominal pain type is usually described in a patient as either diarrhea-predominant (IBS-D), constipation-predominant (IBS-C) or IBS with alternating stool pattern (IBS-A). In some individuals, IBS may have an acute onset and develop after an infectious illness characterised by two or more of the following; fever, vomiting, acute diarrhoea, positive stool culture. This post infective IBS has been termed "Post infectious IBS" (IBS-PI) and is acute onset Rome II criteria positive. This condition is more homogenous, being mostly D-IBS and is drawing much clinical investigation.

Symptoms

The range of Symptoms relating to IBS is relatively broad, but the main symptom is usually abdominal pain or discomfort associated with changes in bowel habits in the absence of any apparent structural abnormality. The pain is commonly relieved by defecating or modulated by other triggers of gut motility. Generally there is no pain when patients are asleep. Symptoms usually start in young adulthood.

There appears to be an overlap of IBS with stress, chronic pelvic pain, fibromyalgia, chronic fatigue syndrome, the American folk medicine use of term hypoglycaemia, and various mental disorders (in a small minority). While no single explanation for this phenomenon exists, it does strengthen the view that there is a neurological and psychological component to IBS. Recent studies indicate that presynaptic neural effects secondary to the release of histamine (part of immune response) is likely related to these problems.[1]

The role of hormones in IBS is not yet fully understood. Menstruation frequently triggers or exacerbates IBS symptoms,[2] while pregnancy and menopause can either worsen or improve symptoms. Hormone replacement therapy is associated with an increased risk of developing IBS.[3]

Diagnosis

Diagnostic criteria

In 1978 Manning et al. found [4], from questionnaire data, that IBS sufferers reported four common symptoms. The Manning Criteria was established to distinguish organic causes for symptoms from those of IBS. In 1992 the Rome I Criteria were established by a multinational committee of specialists, which further refined the Manning Criteria. In 1998 the Rome Working Team proposed changes to the definition and diagnostic criteria for IBS to reflect new research data, and to improve clarity.

Physicians rely on a variety of procedures and laboratory tests to confirm a diagnosis. The cardinal requirement for the diagnosis of IBS is abdominal pain. The Rome II Criteria is used to diagnose IBS after a careful examination of a sufferer's medical history and physical abdominal examination which looks for any 'red flag' symptoms.

According to the Rome II committees of the Functional Brain Gut Research Group,[5] IBS can be diagnosed based on at least 12 weeks, which need not be consecutive, of the preceding 12 months, there was abdominal discomfort or pain that had two out of three of these features:[6]

  • Relieved with defecation; and/or
  • Onset associated with a change in frequency of stool; and/or
  • Onset associated with a change in form (appearance) of stool.

Symptoms that cumulatively support the diagnosis of IBS:

  • Abnormal stool frequency (for research purposes, “abnormal” may be defined as greater than 3 bowel movements per day and less than 3 bowel movements per week);
  • Abnormal stool form (lumpy/hard or loose/watery stool);
  • Abnormal stool passage (straining, urgency, or feeling of incomplete evacuation);
  • Passage of mucus;
  • Bloating or feeling of abdominal distention.

Supportive Symptoms of IBS:

A) Fewer than three bowel movements a week
B) More than three bowel movements a day
C) Hard or lumpy stools
D) Loose (mushy) or watery stools
E) Straining during a bowel movement
F) Urgency (having to rush to have a bowel movement)
G) Feeling of incomplete bowel movement
H) Passing mucus (white material) during a bowel movement
I) Abdominal fullness, bloating, or swelling

Diarrhea-predominant: At least 1 of B, D, F and none of A, C, E; or at least 2 of B, D, F and one of A or E. Hard or lumpy stools do not qualify.
Constipation-predominant: At least 1 of A, C, E and none of B, D, F; or at least 2 of A, C, E and one of B, D or F.

Red Flag symptoms which are NOT typical of IBS:

  • Pain that awakens/interferes with sleep
  • Diarrhea that awakens/interferes with sleep
  • Blood in the stool (visible or occult)
  • Weight loss
  • Fever
  • Abnormal physical examination

An update to these criteria was issued at the ROME III conference and published in May, 2006. [7] The validity of subtypes is called into question: "The validity and stability of such subtypes over time is unknown and should be the subject of future research." and "Because of the characteristic symptom instability, we prefer the terms IBS with constipation and IBS with diarrhea instead of constipation- and diarrhea-predominant IBS. In this categorical system, many people whose features place them close to a subtype boundary change pattern without a major change in pathophysiology. Moreover, the heterogeneity and variable natural history of IBS significantly limit clinical trials of motility-active drugs and drug therapy in practice."

In addition to meeting these positive criteria patients have initial laboratory testing with a complete blood count, basic chemistry panel, and an erythrocyte sedimentation rate. Diagnostic accuracy for IBS is over 95% when Rome II criteria are met, history and physical exam do not suggest any other cause, and initial laboratory testing is negative.

In the past it was thought that the diagnosis of Irritable Bowel Syndrome relied on a diagnosis of exclusion. That is, if one cannot find a cause then IBS is the diagnosis. Currently the diagnosis of Irritable Bowel Syndrome relies on meeting Rome II inclusion criteria and excluding other illnesses based on history, physical exam, and laboratory testing. Although the Rome II criteria were not designed to be a management guideline, it is currently a "gold standard" for the diagnosis of IBS. Unfortunately an IBS diagnosis is still only useful as tool to rule out more serious problems unless further investigation is employed to discern an addressable condition.

Differential diagnosis

The diagnosis of a functional bowel disorder always presumes the absence of a structural or biochemical explanation for the symptoms. This can be excluded via:

Initial screening only requires a history and physical exam, as well as a full blood count, electrolytes, renal function, and an erythrocyte sedimentation rate. Additional testing is done when there is a poor response to treatment.

While these modalities may be employed to rule out other causes of abdominal symptoms, they are not necessary to make a diagnosis of IBS. Depending on local practice, many doctors avoid overdiagnosing if the history is clearly suggestive of a functional bowel disorder.

Although few doctors will run a complete set of testing, when it is performed the underlying cause of their symptoms can often be found and treated. Testing for bacterial abnormalities, food allergies (IgG type allergies), and parasites are particularly useful though often not covered by insurance and thus not performed.[8]

Diagnostic tests

Researchers have demonstrated abnormal sensitivity in IBS patients to intestinal and esophageal distention with balloons. However, this approach has not yet become available as a diagnostic test since the diagnostic accuracy is low and clinical utility is not yet high enough. The diagnosis of IBS is made by exclusion as there are no serological (blood) markers. A history of major life stress, anxiety, depression, abuse, or preceding infection may be suggestive, yet not diagnostic. Organs outside the gastrointestinal system may be sources of referred symptoms, and abnormalities should be ruled out. Red flags arguing against an IBS diagnosis include bleeding, weight loss, difficulty swallowing, nocturnal symptoms, incontinence, or onset of symptoms over the age of 50. Screening for ruling out colorectal cancer is still applicable.

Pathophysiology

IBS is highly prevalent in the Western world, but despite the advancement of many theories, no clear cause has yet been established. Increasing prevalence in developing countries suggests some possibile links to diet and cultural factors.[9] Evidence of visceral hyperalgesia (increased sensitivity to noxious stimuli in the gut) includes perception of pain from distention of a rectal balloon at smaller volumes than in normal patients. However somatic sensitivity testing, such as in controlled pressure on the nails of the hand show that IBS patients have greater pain tolerance than normal patients. The association of IBS with stress is less clear, but studies have shown that there is a high likelihood of reports of previous physical and sexual abuse in some IBS patients. Socially stressful situations seem to play a role in the presence of symptoms but are not known to actually affect the underlying disease.

Onset of IBS after an episode of enteritis has been described (partially after use of antibiotics). In these cases, a prolonged immune reaction may be the cause. Patients with IBS after a viral illness may have a self limited course of only 3 to 6 months duration.

IBS is widely regarded as a conglomeration of disorders with similar symptoms but a different etiology (root cause). As with many other medical conditions, there is a lot of speculation about causes, including in the field of alternative medicine.

Bacteriological Issues

Two studies from the same research group found that 78% to 84% of patients with IBS had bacterial overgrowth. In patients with evidence of bacterial overgrowth, those treated with neomycin had a >/= 35% reduction in clinical response (ie, improvement) compared with an 11% reduction in patients on placebo.[10][11] Subsequent studies have also identified significant bacterial overgrowth and demonstrated substantial reduction in symptoms following treatments, especially with antibiotics specific to the strains that are in excess.

Stress

Stress—feeling mentally or emotionally tense, troubled, angry, or overwhelmed—may trigger symptoms in people with IBS. The colon has a vast supply of nerves that connect it to the brain. These nerves control the normal rhythmic contractions of the colon and cause abdominal discomfort at stressful times. People often experience cramps or "butterflies" when they are nervous or upset. But with IBS, the colon can be overly responsive to even slight conflict or stress. Stress also makes the mind more tuned to the sensations that arise in the colon and makes the stressed person perceive these sensations as unpleasant.[12]

Some evidence suggests that IBS is affected by the immune system, which fights infection in the body. The immune system is also affected by stress. For all these reasons, stress management is an important part of treatment for IBS. Stress management comprises:

  • stress reduction (relaxation) training and relaxation therapies, such as meditation
  • counseling and support
  • regular exercise such as walking or yoga
  • changes to the stressful situations in your life
  • adequate sleep

It should be noted that the gut has its own nervous system - the enteric nervous system which has reciprocal connections to the main brain. the discovery of this has lead to the development of the field of Neurogastroenterology.

Treatment

One of the most important therapeutic measures is reassuring the patient that they have no fatal or otherwise threatening disease, as this is the major concern of patients seeking medical help. Dietary advice may be given and medication is an option in most forms.

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

Diet

Repeated studies indicate that there are various causes of the set of IBS symptoms, including food allergies and sensitivities. Argument continues on the definition of cause as regards IBS and food allergies, but studies demonstrate that IBS symptoms are sometimes caused by immune response to foods and exclusion of those foods to which the immune system is responding results in reduction or elimination of IBS symptoms, a cause and effect link.[14]

Definitive determination of dietary issues can be accomplished by testing for the physiological effects of specific foods. The ELISA food allergy panel can identify specific foods to which a patient has a reaction. Other testing can determine if there are nutritional deficiencies secondary to diet that may also play a role. Removal of foods causing IgG immune response as measured using the ELISA food panel has been shown to substantially decrease symptoms of IBS in several studies.[15]

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 can provoke an over-reaction of the gastrocolic response in some patients with IBS due to their heightened visceral sensitivity, and this can lead to abdominal pain, diarrhea, and/or constipation.

There are a number of diet changes a person with IBS can make to prevent the over-reaction of the gastrocolic reflex and lessen pain, discomfort and bowel dysfunction. Having soluble fiber foods and supplements, substituting soy or rice products for dairy, being careful with fresh fruits and vegetables that are high in insoluble fiber, and eating regular small amounts can all help to lessen the symptoms of IBS; Foods and beverages to be avoided or minimized include red meat, oily or fatty (and fried) products, dairy (even when there is no lactose intolerance), solid chocolate, coffee (regular and decaffeinated), alcohol, carbonated beverages (especialy those also containing sorbitol) and artificial sweeteners. However care should be taken to avoid adding foods to the diet to which the patient is allergic or intolerant.[16] Several of the most common dietary triggers are well-established by clinical studies at this point; research has shown that IBS patients are hypersensitive to fats, insoluble fibers, and fructose.[17][18][19] It also appears that some foods are more difficult for the gut as evidenced by elevated food-specific IgG4 antibodies being present,[20] [21] while others increase colonic contractions, which may be painful, due to increased visceral sensitivity in IBS sufferers.[22]

Medication

Medications may consist of stool softeners and laxatives in constipation-predominant IBS, and antidiarrheals (e.g., opioid or opioid analogs such as loperamide (Imodium®), or diphenoxylate (Lomotil®)) in diarrhea-predominant IBS for mild symptoms. For severe diarrhea-predominant IBS, more potent opioids are commonly employed, such as codeine or propoxyphene (Darvon®); refractory cases may even be treated with paregoric, or, more rarely, deodorized tincture of opium or morphine sulfate. The use of opioids remains controversial due to the potential risk of tolerance, physical dependence and psychological dependence (addiction). The use of antispasmodic drugs (e.g. anticholinergics such as hyoscine) has not shown conclusive beneficial results due to a large number of individuals who respond to the placebo effect; however, in general, although the cause is unknown, the placebo effect remains higher than normal for sufferers of IBS for all medications. Antispasmodic drugs are also available in combination with tranquilizers or barbiturates, such as Librax® (chlordiazepoxide and clidinium) and Donnatal® (mixed salts of belladonna alkaloids and phenobarbital), respectively.

Low dosage of tricyclic and SSRI antidepressants have shown to be the most widely prescribed medications for helping to relieve symptoms of visceral sensitivity (pain) and diarrhea or constipation respectively. Newer drugs include alosetron, a selective 5-HT3 antagonist for IBS-D, which is only available for women in the United States under a restricted access program, due to severe risks of side-effects if taken mistakenly by IBS-A or IBS-C sufferers. Cilansetron, also a selective 5-HT3 antagonist, is undergoing further clinical studies in Europe for IBS-D sufferers. In 2005, Solvay Pharmaceuticals withdrew Cilansetron from the United States regulatory approval process after receiving a "not-approvable" action letter from the FDA requesting additional clinical trials. Tegaserod, a selective 5-HT4 antagonist for IBS-C, is available for relieving IBS constipation in women and chronic idiopathic constipation in men and women. The USA FDA has issued two warnings about the serious consequences of Tegaserod. In 2005, Tegaserod was rejected as an IBS medication by the European Union; however, it is available in some other countries, including the United States. Tegaserod, marketed as Zelnorm in the United States, is the only agent approved to treat the multiple symptoms of IBS, including constipation, abnominal pain and bloating.

Enteric coated peppermint oil capsules have been shown to relieve IBS symptoms in adults and children,[23] but they are contraindicated in patients with the comorbidity of gastroesophageal reflux disease.

Recent studies have suggested that rifaximin could be used as an effective treatment for abdominal bloating and flatulence,[24] giving more credibility to the potential role of bacterial overgrowth in some patients with IBS.[25]

Marijuana is also associated with symptom relief in sufferers of IBS. Although illegal in the United States, it has been prescribed to patients in nations such as Canada. Some of the argued benefits of cannabis are the reduction of pain and nausea, appetite stimulation, and assisting in falling sleep.

Brain-Gut and other

Gut-directed or gut-specific hypnotherapy or self-hypnosis is one of the most promising areas of IBS treatment. Current research shows that symptom reduction/elimination from IBS hypnotherapy can last at least five years.[26] There is a strong brain-gut component to IBS, and cognitive therapy may improve symptoms in a proportion of patients in conjunction with antidepressants.[27] Ongoing investigational research also involves relationships to food allergies (as measured through blood antibody analysis), poor bacterial balance and the increase of probiotics,[28] parasites, scar tissue that affects bowel motility, and bacterial overgrowth,[10] as a cause of symptoms.

Alternative Treatment

Probiotics are generally accepted to be potentially beneficial strains of bacteria and yeast, often found in the human gut. One research study has shown a clear link between the ingestion of Lactobacillus plantarum LP299V and sufferers of Irritable Bowel Syndrome who reported resolution of their abdominal pain.[29] Another study showed the utility of B. infantis 35625, a strain of Bifidiobacteria in normalizing bowel movement frequency in sufferers of Irritable Bowel Syndrome.[30] Some practitioners of Integrative Medicine, now recommend a strain of Lactobacillus known commonly as "LGG" after its discoverers Gorbach and Goldin. This strain in particular has shown an ability to endure the acidic environment of the stomach and survive until presentation to the intestinal tract.[31]

Many sufferers of IBS seek relief from Acupuncture, a component of Traditional Chinese Medicine and a discipline representing some of the oldest and most used medical procedures in the world. This discipline continues to find increasingly widespread acceptance in the United States, and it is estimated that nearly 8.7 million Americans have sought its benefits.[32] One practitioner of TCM asserts that IBS has become a bit of a "garbage diagnosis" for some medical practitioners. Traditional Chinese Medicine does not recognize the Western diagnosis of IBS per se, as the named condition has no definitive single test for diagnosis, clear cause, or cure. Traditional Chinese Medicine approaches IBS on an individual symptom-by-symptom basis, rather than recognizing a standard "IBS" diagnosis, which then warrants a blanket "IBS" treatment.[33] The concept of Qi is important in Acupuncture, as obstructions to its proper flow throughout the body are considered a contributing factor to illness. Details of the specific mechanisms through which Qi function remain as yet unexplained by Western Scientific methods. According to the National Institutes of Health:[34]

Preclinical studies have documented acupuncture's effects, but they have not been able to fully explain how acupuncture works within the framework of the Western system of medicine that is commonly practiced in the United States.

Epidemiology

Point prevalence is 10 - 20% of the general population of Western countries with a much higher lifetime prevalence. Prevalence is similar in India, Japan and China. IBS is less common in Thailand and rural South African areas. In Western countries, but not in India or Sri Lanka, females have a greater risk of developing IBS.

Of the persons who have symptoms of IBS, only a proportion seeks medical help. However, there is not yet a predictor known for who will seek medical help and who will not.

Prognosis

IBS is not fatal nor is it linked to the development of other serious bowel diseases. However, due to the chronic pain, discomfort, and other symptoms, work absenteeism, social phobias, and other negative quality-of-life effects can be common in more serious cases. Individuals who find a caring primary caregiver and/or sufficient self-help options should be able to develop a successful treatment program for their symptoms and lead normal lives.

See also

External links

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