IRRITABLE BOWEL SYNDROME

Irritable bowel syndrome (IBS) or spastic colon affects 10-20 percent population. It is likely that you or someone you know has irritable bowel syndrome. But what is this irritable bowel syndrome or spastic colon or IBS?

Irritable bowel syndrome

IBS is a symptom based diagnosis of unclear etiology. It should not be confused with diverticulosis or diverticultis. Irritable bowel syndrome is probably is not a single disease. More likely, IBS is comprised of multiple diseases, all lumped into one at the present time for lack of understanding its pathogenesis. Infantile colic is considered by many to be a variant of IBS in infants and kids.

Features of irritable bowel syndrome and Rome criteria

Irritable bowel syndrome is a functional disorder characterized by chronic (at least three months in the preceding one year) abdominal pain and a disturbance of bowel habit. The disturbed bowel habit of IBS may manifest as diarrhea, constipation or alternating diarrhea with constipation. Pain frequently improves with defecation. A waxing and waning pattern of symptoms is seen in most patients. The precise conglomeration of symptom complex is defined under ROME III criteria.

What causes irritable bowel syndrome?

The pathogenesis of irritable bowel syndrome remains an enigma and no single etiology fits all cases. IBS is predominantly seen in young females but can be seen in adults of any age and either sex. It is more prevalent among Caucasian Americans than African Americans. Motility disorder has been frequently implicated; however no consistent motility pattern can be demonstrated. Visceral hypersensitivity (pain with a stimulus not severe enough to cause pain in healthy subjects) is seen in many patients. Autonomic dysregulation has also been implicated. A dysfunction of 5-HT system is supected in many cases. Stress does not cause it but does tend to exacerbate symptoms. Food allergy or intolerance may be present in some cases.

Many patients attribute the onset of disease to a bout of flu-like illness e.g. viral gastroenteritis, travelers diarrhea. Low grade inflammation in the gut can be documented in many cases. Several authors claim small intestinal bacterial overgrowth to be the cause in most cases of IBS although these observations have not been confirmed by others.

IBS consensus

Overall, in the absence of clear cut cause, a bio-psychosocial model for pathogenesis for irritable bowel syndrome has been proposed. This model emphasizes the role of mind-body interactions with the environment. In this context, it should be noted that there is an increased prevelance of certain chronic pain disorders in IBS patients, e.g. functional dyspepsia, fibromyalgia, chronic fatigue syndrome, interstitial cystitis, chronic back pain etc.

Diagnostic strategy for irritable bowel syndrome

While the diagnosis of irritable bowel syndrome should be positive, physicians frequently perform studies to exclude any treatable cause. The work up for IBS should be individualized and may include complete blood count (CBC), routine chemistries and stool studies. Flexible sigmoidoscopy or colonoscopy may be performed depending upon age and risk for colon cancer and suspicion for alternative diagnosis like inflammatory bowel disease (Crohn's disease and ulcerative colitis). Celiac sprue should be excluded by antibody testing for anti-tissue transglutaminase antibody. The use of anti-gliadin antibody has largely been abandoned.  Anti-endomysial antibody testing is expensive and not cost-effective. Lactose hydrogen breath test may be done to exclude lactose intolerance. Small bowel bacterial overgrowth can be excluded by hydrogen breath test or cultures of small bowel aspirate.

Treatment of irritable bowel syndrome

The management of IBS patients follows a step-wise fashion and is largely symptom based. Realistic goals need to be established. Reassurance with a lot of hand-holding goes a long way in helping patient cope with the symptoms of IBS. Placebo response rate in irritable bowel syndrome may be as high as fifty percent.  High fiber diet and fluid are frequently prescribed as first line of treatment for IBS of all types. Patients with diarrhea may be helped by lactose-avoidance.

Over the counter laxatives or  prescription medication Zelnorm are used in cases with constipation predominant IBS. Of note, Zelnorm was withdrawn from US market on March 30, 2007 because of unacceptable side-effects.

Constipating agents like Imodium and Lomotil may be needed in patients with diarrhea predominant IBS. Lotronex is useful for diarrhea-predominant IBS but has high risk for ischemic colitis. Its availability is limited and its use in IBS has largely been abandoned by most physicians in the US.  Its is not to be used for irritable bowel syndrome of constipation type. Antispasmodic agents e.g. Bentyl are frequently prescribed for abdominal pain associated with irritable bowel syndrome but provide only limited benefit at best.

Small bowel bacterial overgrowth is treated with antibiotics. Gluten-free diet helps patients with Celiac sprue.

Role of antidepressents in irritable bowel syndrome

Low dose tricyclic antidepressants (e.g. imipramine, desipramine) raise the pain threshold and are frequently prescribed to IBS patients not responding to above strategies; however their side-effects can be problematic.  Although frequently prescribed, there is less data about the use of newer antidepressant agents like SSRIs for management of IBS.

Several trials have documented positive impact of probiotics in IBS patients. Cognitive behavioral therapy, hypnosis, IBS classes, yoga, Chinese herbal medicine etc have  also been used successfully in irritable bowel syndrome. Limited data points to efficacy of melatonin (over-the-counter sleep-aid) in IBS.

Comments

[IBS survivor]

It is wise to look for the cause of IBS like you said. The symptoms can be caused by a variety of health problems.

[Raymond Harper]

I have suffered from acid reflux disease for over ten years and have been reading that irritable bowel syndrome and acid reflux disease are linked. Could you please tell me if there is a greater chance of getting irritable bowel syndrome if you already have acid reflux disease?