Differential Diagnosis and Management of IBS -- Update

Summarized by Robert W. Griffith, MD
November 28, 2002 (Reviewed: November 13, 2004)

Introduction

In an earlier article, we discussed recent views on the pathogenesis of irritable bowel syndrome (IBS). Here we summarize the newer approaches to differential diagnosis and management of this extremely common condition.

Diagnosis

Once a diagnosis of exclusion, IBS is now readily defined as 'abdominal pain plus altered bowel motility', with the Rome II criteria providing more precision. However, the differential diagnosis is important, as serious conditions must be excluded from consideration. There is no simple biological marker for IBS. Colonic balloon distension is invasive and not specific enough to justify its use for this purpose.

Age at onset is important; new bowel symptoms over the age of 50 or a history of colon cancer need a full workup to exclude a malignant condition. In people under 50, lactose intolerance should be considered; the amount of milk consumed may provide a clue. However, lactose intolerance and IBS can readily co-exist. Dietary and symptom diaries may be helpful.

Celiac disease may account for 5% of patients with symptoms corresponding to IBS (compared with 0.5% in a non-IBS population). A screen for antiendomysial antibodies can exclude celiac disease. Mild Crohn's disease is rare, but can be detected using radiological examination of the small bowel. Rarely, idiopathic bile-salt malabsorption can confuse the diagnosis, but a therapeutic trial of cholestyramine provides an easy and cheap answer.

Endoscopy should be reserved for patients with continuing diarrhea, where duodenal or colonic biopsy might be useful in excluding celiac disease or microscopic colitis.

Management of IBS

One of the most important steps is to establish good doctor-patient communication. This has been shown to be associated with reduced return visits. It necessitates reassurance that the patient's symptoms and the disorder are indeed real, and not just 'in their head'. The patient should be fully educated about IBS, including its benign prognosis, and possible triggers (dietary factors, stress, gastrointestinal infections, etc). Support groups may be helpful, including those on the Internet. Repeated clinical tests should be avoided, unless there is good reason.

First-line treatment should be dietary modification - for instance, gradual introduction of a low-fiber diet for diarrhea, the reverse for constipation. Obvious precipitants or irritants should be avoided, while a cautious trial of a gluten- or wheat-free diet may be appropriate. Probiotics may be helpful in some patients.

Medications should be used sparingly, and targeted at the patient's individual symptoms. Antispasmodics and anticholinergics are of doubtful efficacy. Loperamide can help diarrhea. Osmotic and stimulant laxatives may be given for constipation, but effects are inconsistent. And tricyclic antidepressants can be invaluable in helping control depressive symptoms; however, selective serotonin reuptake inhibitors (SSRI) have not been shown to be effective in IBS, to date.

'Serotonin' medications

Serotonin (5HT) plays an important role in transmitting impulses from the intestines to the brain, as well as from the brain to the intestines. Infectious and inflammatory conditions are associated with increased 5HT levels in cells of the intestine wall, accompanied by increased gut motility.

The 5HT3 receptor antagonist alosetron has been shown to be effective in diarrhea-predominant IBS, but may provoke ischemic colitis and severe constipation; its use has therefore been restricted.

A 5HT4 partial agonist, tegaserod, is pro-kinetic and is effective in constipation-predominant IBS; it has a good side-effect profile. Further drugs in both these classes are under evaluation.

Alternative treatments

Several drugs from novel classes are in the clinical trial stage. Non-drug approaches include psychotherapy, relaxation techniques, biofeedback, and cognitive-behavior therapy. They can all be of value in individual IBS patients, although formal controlled trials have produced disappointing results.
Hypnotherapy, when confined to IBS patients without overt psychiatric disease, has proven the most successful of the alternative therapies. Chinese herbal medicine (a combination of 20 herbs) was found effective in one clinical trial. Acupuncture, on the other hand, has been shown to be ineffective, as has reflexology.

In a separate article we summarize recent views on the pathogenesis of IBS (see link below).

Source

• Irritable bowel syndrome: a little understood organic bowel disease? N. Talley, R. Spiller, Lancet, 2002, vol. 360, pp. 555--564

Related Links
Pathogenesis of IBS -- Update
Diverticular Disease

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