Irritable Bowel Syndrome

In medicine (gastroenterology), irritable bowel syndrome (IBS) or spastic colon is a group of functional bowel disorders which are fairly common and make up 20–50% of visits to gastroenterologists. There are three forms, dependent on which symptom predominates: diarrhea-predominant (IBS-D), constipation-predominant (IBS-C) and IBS with alternating stool pattern (IBS-A). An important new IBS subtype, post-infectious IBS (IBS-PI), is drawing much clinical investigation.

Features

Symptoms of IBS are abdominal pain or discomfort associated with changes in bowel habits in the absence of any apparent structural abnormality. The pain is typically relieved by defecating.

There appears to be an overlap of IBS with stress, chronic pelvic pain, fibromyalgia and various mental disorders (in a small minority). While no good explanation for this phenomenon exists, it does strengthen the view that there is a neurological and psychological component to IBS.

Diagnosis

Diagnostic criteria

In 1978 Manning et al., found, from questionaire 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 was 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 refelect new research data, and to improve clarity.

The diagnosis of Irritable Bowel Syndrome has relied on a diagnosis of exclusion. Because the symptoms of IBS share the symptoms of so many other intestinal illnesses, it sometimes takes years before a correct diagnosis is made to exclude the obvious, and not so obvious, conditions which present symptoms similar to IBS.

Physicians rely on a variety of procedures and laboratory tests to confirm a diagnosis. The Rome II Criteria, however now defines markers which allows professionals to diagnose IBS after a careful examination of a sufferers medical history and physical abdominal examination which looks for any 'red flag' symptoms.

Red Flag symptoms which are NOT typical of IBS:

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

According to the Rome II consensus conference of the American Gastroenterological Association and international medical societies on functional bowel disorders, the diagnosis of IBS can be made when the following criteria are fulfilled:

At least 12 weeks, which need not be consecutive, in the preceding 12 months of abdominal discomfort or pain that has 2 of 3 features:

1. Relieved with defecation; and/or
2. Onset associated with a change in frequency of stool; and/or
3. 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:

1. Fewer than three bowel movements a week
2. More than three bowel movements a day
3. Hard or lumpy stools
4. Loose (mushy) or watery stools
5. Straining during a bowel movement
6. Urgency (having to rush to have a bowel movement)
7. Feeling of incomplete bowel movement
8. Passing mucus (white material) during a bowel movement
9. Abdominal fullness, bloating, or swelling

Diarrhea-predominant: 1 or more of 2, 4, 6 and none of 1, 3, or 5; or: 2 or more of 2, 4, or 6 and one of 1 or 5. (3. Hard or lumpy stools do not qualify.) Constipation-predominant: 1 or more of 1, 3, 5 and none of 2, 4, or 6;or: 2 or more of 1, 3, or 5 and one of 2, 4 or 6.

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:

• sigmoidoscopy or colonoscopy
• esophagogastroduodenoscopy (EGD, gastroscopy)
• abdominal ultrasound or CT scan
• blood tests: full blood count, liver enzymes, electrolytes, renal function
• stool chemistry (e.g. tests for exocrine pancreas insufficiency and other malabsorption conditions), stool microbiology, fecal fat
• H₂-tests for lactose intolerance and fructose malabsorption
• blood tests or deep duodenal biopsy for celiac disease

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.

Diagnostic tests

A diagnostic test for IBS via assessment of colonic/rectal hypersensitivity using a barostat is currently being discussed. However, sensitivity and specificity are not yet high enough to render the method widely applicable.

Pathophysiology

IBS is highly prevalent in the Western world, but despite the advancement of many theories, no clear cause has yet been established. Hypersensitivity of the gut is a major finding in most IBS patients. The association of IBS with stress is less clear, but studies have shown that there may be a correlation between IBS and prior sexual or physical abuse. Changes in colonic motility and immunologic causes have been discussed, as well as dietary causes.

About 25% of patients develop symptoms after an episode of enteritis (partially after use of antibiotics). In these cases, a prolonged immune reaction is currently discussed as pathogenetic. So far, this is mainly based on experiments in the animal model.

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.

Treatment

One of the most important therapeutic measures is reassuring the patient that he has 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.

Diet

There is no evidence that digestion of food is different in those with IBS compared to those without IBS. Although the exact cause of IBS is not known, there are factors that appear to aggravate symptoms or make a person feel worse. While dietary factors do not cause IBS, they may aggravate symptoms in some persons (IFFGD, 2004).

Many people including physicians have noted a connection to diet. 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.

Although there are a number of diet changes a person with IBS can make to relieve stress on the intestines to lessen pain, discomfort and attacks, these are basically guesswork. Common recommendations usually include having soluble fibre 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 to lessen the symptoms of IBS (Van Vorous 2000). Suggestions as to food and beverages to be avoided or minimised include red meat, oily or fatty (and fried) products, dairy (especially when lactose intolerance is suspected), solid chocolate, coffee (regular and decaffeinated), alcohol, carbonated beverages (especialy those also containing sorbitol) and artificial sweeteners (Van Vorous 2000) although this is all purely anecdotal at this stage. It appears that some foods are more difficult for the gut as evidenced by elevated food-specific IgG4 antibodies being present (Kumar, 2005), while others increase colonic contractions, which may be painful, due to increased visceral sensitivity in IBS sufferers (Mayer, 2004).

Medication

Medications may consist of stool softeners and laxatives in constipation-predominant, and antidiarrheals (loperamide) in diarrhea-predominant IBS for mild symptoms. 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. 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. Tegaserod, a selective 5-HT4 antagonist for IBS-C, has shown to have an excellent safety profile for relieving IBS constipation and chronic idiopathic constipation.

Psychological and other

There appears to be a psychological component to IBS, and cognitive therapy may improve symptoms in a proportion of patients in conjunction with antidepressants (Kennedy et al, 2005). Ongoing investigational research involves relationships to food allergies (as measured through blood antibody analysis), poor bacterial balance and the increase of probiotics (Quigley, 2005), parasites, scar tissue that affects bowel motility, and bacterial overgrowth (Pimentel, 2000), as a cause of symptoms.

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 who work with the sufferer to develop a successful treatment for their symptoms generally can lead more normal lives.

Reference

• Heather Van Vorous. Eating for IBS. 2000. ISBN 1569246009.
• Irritable Bowel Syndrome Self Help and Support Group, (2005). Diagnostic Criteria. Retrieved on Dec. 4, 2005 from http://www.ibsgroup.org/main/diagnosis.shtml
• Kennedy T, Jones R, Darnley S, Seed P, Wessely S, Chalder T. Cognitive behaviour therapy in addition to antispasmodic treatment for irritable bowel syndrome in primary care: randomised controlled trial. BMJ 2005;331:435. PMID 16093252.
• Pimentel M, Chow EJ, Lin HC. Eradication of small intestinal bacterial overgrowth reduces symptoms of irritable bowel syndrome. Am J Gastroenterol 2000;95:3503-3506.
• Quigley EM. The use of probiotics in functional bowel disease. Gastroenterol Clin North Am. 2005 Sep;34(3):533-45, x
• Thompson WG, Longstreth GL, Drossman DA et al. (2000). Functional Bowel Disorders. In: Drossman DA, Corazziari E, Talley NJ et al. (eds.), Rome II: The Functional Gastrointestinal Disorders. Diagnosis, Pathophysiology and Treatment. A Multinational Consensus. Lawrence, KS: Allen Press. ISBN 0965683729.
• Wangen, Dr. Stephen, (2005) "The Irritable Bowel Syndrom Solution" Innate Health Group. ISBN 0976853787.

External links

• International Foundation for Functional Gastrointestinal Disorders - Evidence based information about IBS
• UNC Center for Functional GI & Motility Disorders - IBS Education and Research