Irritable Bowel Syndrome (IBS): Diagnosis

It is estimated that the typical patient visits an average of three different physicians over a three-year span before receiving the diagnosis of irritable bowel syndrome (IBS). Because there is an absence of distinguishing physical or laboratory markers in IBS, the diagnosis is based on patient symptoms. The diagnosis must be confirmed by the exclusion of other conditions, such as malabsorptive disorders, metabolic disorders, dietary factors, infection, inflammatory bowel disease, psychological disorders, or gynecological disorders.

The diagnostic criteria for irritable bowel syndrome (IBS), known as the ROME II criteria (Table 1), were recently updated by the International Working Party, a multinational panel of gastroenterologists. The ROME II criteria require patients to report abdominal pain for at least twelve weeks (consecutive or nonconsecutive) of the year that has two of three characteristics: 1) relieved upon defecation, 2) associated with a change in stool frequency, and/or 3) associated with a change in stool form. The criteria, intended for use in combination with a thorough patient history, physical examination, and laboratory evaluation, also provide the clinician with a list of common symptoms that support a diagnosis of irritable bowel syndrome (IBS).

Table 1:

Detailed information regarding the nature, severity, location, and timing of symptoms is gathered during the patient history. Medications that can precipitate IBS-like symptoms, such as anticholinergic agents or antibiotics (Table 2), may be identified. Certain food products can be an exacerbating factor in the disorder and exclusion of caffeine, alcohol, chocolate, and dairy products (Table 3) may be necessary.

The physical exam in an irritable bowel syndrome (IBS) patient will typically be normal except for mild abdominal tenderness. Laboratory testing is based upon predominant symptoms and may include a complete blood count, erythrocyte sedimentation rate, C-reactive protein, thyroid and liver function tests, and a stool evaluation and culture. Clinical features that are not consistent with IBS and necessitate further work-up or referral include onset of symptoms after age 50, nocturnal symptoms, and warning signs of other diseases (Table 4).

Table 2:

Table 3:

Table 4:

Metamucil

Lyrica

Colestid

Tofranil

Prozac

Jennifer Bowles

Jennifer is a clinical pharmacologist. She helps doctors of all medical specialties choose medications. Jennifer consults about drug dosage, interactions, and side effects.