Irritable bowel syndrome made simple

In most cases,  colonic imaging  is not necessary to diagnose IBS.
In most cases, colonic imaging is not necessary to diagnose IBS.

At a glance

  • Neither colonic imaging nor a full panel of blood, serum chemistries, and stool analyses are necessary in most cases.
  • There is insufficient evidence to support a position on food allergy or exclusion diets.
  • Antidepressants have been shown to be superior to placebo for IBS symptoms including abdominal pain.
  • There is some evidence of the benefits of Chinese herbal therapy. Trials of acupuncture have been inconclusive.

The American College of Gastroenterology has issued a new Evidence-Based Systematic Review on the Management of Irritable Bowel Syndrome, its first since 2002. In the intervening years, new drugs have become available and others withdrawn, and investigators have added a wealth of data on which to base clinical decisions.

“Irritable bowel syndrome (IBS) is a disorder that is seen by virtually everyone on the front line,” says Lawrence J. Brandt, MD, professor of medicine and surgery at Albert Einstein College of Medicine, Bronx, N.Y., and chair of the task force that produced the review. “This condition occupies a significant amount of time in primary care.”

According to Dr. Brandt, one point the revised position statement emphasizes is the impact of IBS. “We spent more time on the burden of the illness,” he says. “There's an increasing appreciation that IBS is a real disease, a common disease, and not something in the patient's head.”

A straightforward diagnosis

The 2009 review represents an effort to clarify and simplify terms and recommendations associated with IBS. “We went out of our way to make this review readable,” says Dr. Brandt.

In keeping with this ideal, the task force bypassed the diverse criteria sets that have been proposed for IBS diagnosis (i.e., Manning, Kruis, and Rome I, II, and III) to formulate a simpler, clinically more usable definition that incorporates their key features: “Abdominal pain or discomfort that occurs in association with altered bowel habits over a period of at least three months.”

IBS is not a diagnosis of exclusion. Alarm features (e.g., rectal bleeding, weight loss, anemia, fever) must be followed up, “but in their absence, extensive diagnostic testing is no longer recommended,” says Dr. Brandt. Neither colonic imaging nor a full panel of blood, serum chemistries, and stool analyses are necessary in most cases.

Serologic screening for celiac disease may be indicated in apparent diarrhea-predominant (IBS-D) or mixed IBS (IBS-M) when background frequency of the condition suggests significant pretest probability.

Diet and dietary supplements

In light of widespread patient concern (60% of IBS patients believe food exacerbates their symptoms), the review pays special attention to diet. However, Dr. Brandt points out that there is insufficient evidence to support a position on food allergy or exclusion diets. Data on whether patients can reliably identify foods that cause their symptoms are inconsistent.

Because lactose intolerance is more prevalent among IBS patients than healthy controls, the guidelines recommend clinicians ask about links between lactose ingestion and symptoms and consider hydrogen breath testing in ambiguous cases.

Probiotic dietary supplements for IBS have aroused interest and controversy. Considerably more data have been collected recently, but the diversity of organisms and doses in products used in various studies makes it impossible to draw firm conclusions. Dr. Brandt's review reports that among commonly used single strains, Lactobacilli appear to have little impact, while there is a “trend” for Bifidobacteria to improve overall symptoms. Probiotic combinations may be efficacious as well.

For the most part, studies of fiber supplements have been small, short-term, and of questionable design, but within these limitations, they have shown psyllium hydrophilic mucilloid to reduce global symptoms, and wheat and corn bran to be ineffective.

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