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, dependant on which symptom predominates: diarrhea-predominant (IBS-D), constipation-predominant (IBS-C) and IBS with alternating stool pattern (IBS-A).

Contents

1 Features

2 Diagnosis

2.1 Diagnostic criteria
2.2 Differential diagnosis
2.3 Diagnostic tests

Features

Symptoms of IBS are abdominal pain or discomfort associated with changes in bowel habits in the absence of any structural abnormality. Colonic hypersensitivity is a sensitive but less specific sign of IBS. 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 component to IBS.

Diagnosis

Diagnostic criteria

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:

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.

Differential diagnosis

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

colonoscopy
esophagogastroduodenoscopy (EGD)
abdominal ultrasound
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

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 ("trash can"). As with many other medical conditions, there is a lot of speculation about causes, including in the field of alternative medicine.

Treatment

The most important therapeutic measure is reassuring the patient that he has no fatal or otherwise threatening disease, as this is the major concern of patients seeking medical help. Dependent on symptoms, treatment can consist of dietary advice, stool softeners and laxatives in constipation-predominant, and antidiarrheals (loperamide) in diarrhea-predominant IBS. The use of antispasmodic drugs (e.g. anticholinergics such as hyoscine) is not encouraged as the therapeutic benefit over placebo is hardly proven. Newer drugs include alosetron and tegaserod, both of which are heavily advertised but appear to have only a limited effect with the risk of side-effects.

As there appears to be a psychological component to IBS, psychotherapy is occasionally advised. Though not specifically indicated for IBS, the use of antidepressant drugs (e.g. amitriptyline in a low dosage or an SSRI) to treat the symptoms is common and has positive effects for some patients.

Diet

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. Common recommendations usually include having soluble fibre, soy products, fresh fruit and vegetables, and eating regular small amounts should lessen the symptoms of IBS. 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). Some are more difficult to digest, while others increase colonic contractions, which may be painful.

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 to develop 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 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 lucky enough to find a successful treatment for their symptoms can lead normal lives.

Reference

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.
Heather Van Vorous. Eating for IBS. 2000. ISBN: 1569246009.

Health science - Medicine - Gastroenterology

Diseases of the esophagus - stomach