New Guidelines Designed to Help Diagnose Chronic Diarrhea

A newly published official guideline for diagnosing chronic watery diarrhea was established to aid clinicians in choosing appropriate laboratory tests to exclude other diagnoses in the setting of suspected functional diarrhea or diarrhea-predominant irritable bowel syndrome (IBS-D).

The guidelines, “Clinical Practice Guidelines on the Laboratory Evaluation of Functional Diarrhea and Diarrhea-Predominant Irritable Bowel Syndrome in Adults (IBS-D)”, which will be in force for five years, were developed by the American Gastroenterological Association Clinical Practice Guideline Committee and were approved by the association’s governing board.


These guidelines apply to the evaluation of immunocompetent adult patients with “watery” diarrhea of at least four weeks duration. This would exclude those patients with bloody diarrhea; diarrhea with signs of fat malabsorption; presentations with alarm features, such as weight loss, anemia and hypoalbuminemia; those patients with a family history of inflammatory bowel disease (IBD), colon cancer, or celiac disease; and those with a travel history to regions with recognized specific diarrhea-related pathogens.

Some key recommendations include: (1) testing for celiac disease (an important cause of chronic diarrhea) with IgA tissue transglutaminase and a second test to detect celiac disease in the setting of IgA deficiency; (2) testing for Giardia, a common cause of watery diarrhea that can be readily treated; (3) testing for bile acid diarrhea, which may be due to excess production or decreased absorption of bile acids, which then reach the colon and can cause watery diarrhea. The guideline suggested not using erythrocyte sedimentation rate or C-reactive protein to screen for IBD, and not testing for ova and parasites other than Giardia.

“When managing patients with chronic watery diarrhea, it is important for health care providers to determine whether it is being caused by organic disease or a functional disorder, such as functional diarrhea or irritable bowel syndrome with diarrhea,” said first author Dr. Walter Smalley, professor of medicine at Vanderbilt University School of Medicine (Nashville, TN, USA). “Both functional diarrhea and IBS-D are clinical diagnoses with no defining laboratory tests. A workup to exclude all organic disease is impractical, expensive, and potentially dangerous to patients if false-positive tests result in further invasive testing. The AGA guideline on evaluation of chronic diarrhea is intended to reduce practice variation and promote high-quality and high-value care for this patient population.”

The guidelines were published in the September 2019 issue of the journal Gastroenterology.

Related Links:
American Gastroenterological Association
Vanderbilt University School of Medicine