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Irritable bowel syndrome (IBS)

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Overview of Irritable bowel syndrome

Irritable bowel syndrome (IBS) is a GI disorder characterized by abdominal pain and discomfort associated with altered bowel habits that are not explained by any mechanical, biochemical or inflammatory cause. Highly prevalent in the western population, studies had revealed that IBS affects approximately 10–15% of the general population and has a large impact on quality of life and healthcare costs.1

A motility disorder of the GI tract, IBS is essentially functional in nature with definite psychosomatic basis. The etiology and pathophysiology of IBS is considered to be multifactorial. The severity of the symptoms and their effects on the patient’s quality of life guide the diagnosis and management of IBS. The diagnosis depends on the symptoms and exclusion of the related pathological diseases.

The standard therapy of IBS generally involves a symptom-directed approach, which includes antidiarrheal agents for bowel frequency, soluble fiber or laxatives for constipation and smooth muscle relaxants and antispasmodics for pain.2

Pathophysiology of Irritable bowel syndrome

The factors associated in the pathophysiology of IBS include altered GI motility, increased gut sensitivity and increased intestinal contractions. The following are the proposed mechanisms in IBS:3

  • Stimuli in the form of luminal compressions, diets, local GI irritants
  • Stimulation of enteric nervous system
  • Stimulation of central nervous system
  • Changes in afferent stimulation in enteric nervous system
  • Increased afferent reflex
  • Altered intestinal motility and sensation
  • Abdominal pain and altered bowel habits

Factors such as heredity, abnormal motility, myoelectric dysfunction, lactose deficiency, food intolerance, drugs, endocrines, hormones, prostaglandins, infections, infestations and stress factors have all been implicated in the pathogenesis of IBS.3

Clinical Features of Irritable bowel syndrome

Symptoms consistent with IBS include the following:

  • Abdominal pain that is often precipitated by meals, for at least 12 weeks (which need not be consecutive) in the preceding 12 months, with two of the following features:
  • Relief with defecation
  • Onset associated with a change in stool frequency
  • Onset associated with a change in form or appearance of stool
  • Alternating diarrhea and constipation.
  • Altered stool passage such as straining, urgency or tenesmus (feeling of incomplete emptying after defecations).
  • Abdominal distension and flatulence.
  • Passage of mucus in the stool.

Diagnosis of Irritable bowel syndrome

Effective history taking is the key to the diagnosis of IBS. The diagnosis should be based on positive findings rather than on investigations to exclude other disorders. Current evidence does not support the routine use of blood tests, stool studies, breath tests, abdominal imaging or lower endoscopy to exclude organic GI disease in patients with typical IBS symptoms without alarming features.4

Presence of abdominal pain or discomfort associated with chronic altered bowel habits are the mainstay in diagnosis, while the supportive criteria may be used to further classify IBS as constipation-predominant or diarrhea-predominant. Although findings on physical examination are usually normal, nonspecific abdominal tenderness or a palpable, tender colon may occasionally be present.

However, in presence of alarming features or persistent nonresponse to symptomatic therapies, a more detailed diagnostic evaluation depending upon the patient’s predominant symptoms should be conducted. Traditional alarming features include bleeding, anemia, weight loss and older age at onset.

Management of Irritable bowel syndrome

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The treatment approach of IBS depends on the intensity of symptoms and the degree of other comorbid conditions. Initial treatment should include reassurance, stress management and relaxation techniques. Further treatments are based on the type and severity of symptoms and these includes pharmacologic agents, dietary modification and various nonclinical therapeutic interventions such as psychotherapy and hypnotherapy.

Pharmacotherapy of Irritable bowel syndrome

The medical therapy (anticholinergics, antispasmodics and newer IBS-specific agents) is used more frequently in patients with moderate-to-severe symptoms and is occasionally accompanied by the use of low-dose tricyclic antidepressants (TCAs) and/or other psychiatric medications. Patients with more severe symptoms often require psychotropic medications.5

Treatment strategies for IBS focus on the predominant symptoms. In diarrhea-predominant IBS, loperamide and the 5-HT3 receptor antagonist (alosetron) are efficacious. In constipation-predominant IBS, fiber and bulk laxatives are preferred although their efficacy is variable. The 5-HT4 receptor agonist (tegaserod) is efficacious in patients with IBS and constipation. In patients with IBS and abdominal pain, antispasmodics and TCAs can be used.6

For IBS patients with excessive abdominal bloating, studies suggest that eradication of intestinal bacteria with antibiotics and bacterial reconstitution with probiotics may reduce flatulence and abdominal distension.7,8

Diet Recommendations of Irritable bowel syndrome

Diet recommendations are based on the existing symptoms. There are different dietary recommendations for constipation, diarrhea, pain or bloating. The dietary triggers of IBS include caffeine, citrus, corn, dairy lactose, wheat and wheat gluten. Lactose and caffeine may particularly be associated with diarrhea-predominant IBS.

Recent study had revealed that appropriate identification of food sensitivity in IBS patients not responding to standard therapy gives a sustained clinical response and improves the quality of life.9

The following are some steps that help to reduce symptoms of IBS:

  • Avoid caffeine.
  • Reduce legumes in the diet.
  • Increase fiber intake.
  • Drink more water.
  • Avoid smoking.
  • Effective stress management.

Psychotherapy and Behavioral Techniques

Psychotherapy may be helpful for motivated patients, particularly if bowel symptoms are of short duration, abdominal pain is not constant and there are overt signs of anxiety or depression. Techniques such as relaxation training, meditation, stress management and hypnosis may produce sustained reduction in somatic symptoms.3


1.Hammerle CW, Surawicz CM. Updates on treatment of irritable bowel syndrome. World J Gastroenterol. 2008; 14(17): 2639–2649.

2.Farthing MJ. Treatment options in irritable bowel syndrome. Best Pract Res Clin Gastroenterol. 2004; 18(4): 773–786.

3.Singh RK, Pandey HP, Singh RH. Irritable bowel syndrome: Challenges ahead. CurSci. 2003; 84(12): 1525–1533.

4.Cash BD, Chey WD. Irritable bowel syndrome - An evidence-based approach to diagnosis. Aliment Pharmacol Ther. 2004; 19(12): 1235–1245.

5.North CS, Hong BA, Alpers DH. Relationship of functional gastrointestinal disorders and psychiatric disorders: Implications for treatment. World J Gastroenterol. 2007; 13: 2020–2027.

6.Cremonini F, Talley NJ. Diagnostic and therapeutic strategies in the irritable bowel syndrome. Minerva Med. 2004; 95(5): 427–441.

7.Chang HY, Kelly EC, Lembo AJ. Current gut-directed therapies for irritable bowel syndrome. Curr Treat Options Gastroenterol.2006; 9(4): 314–323.

8.Spiller P. Review article: Probiotics and prebiotics in irritable bowel syndrome (IBS). Aliment Pharmacol Ther. 2008 Jun 4. (Epub ahead of print).

9.Drisko J, Bischoff B, Hall M, McCallum R. Treating irritable bowel syndrome with a food elimination diet followed by food challenge and probiotics. J Am Coll Nutr. 2006; 25(6): 514–522.

Written by: Saptakee sengupta
Date last updated: April 18, 2015

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