Guidelines: AGA Issues Guidelines for Laboratory Evaluation of Functional Diarrhea, IBS-D

Man suffering stomach ache sitting on a couch in the living room at home
Recommendations aim to help clinicians in choosing appropriate laboratory tests to exclude other diagnoses in the setting of suspected functional diarrhea or diarrhea-predominant irritable bowel syndrome.

Guidelines for the laboratory evaluation of both functional diarrhea and diarrhea-predominant irritable bowel syndrome (IBS-D) have been released in Gastroenterology by the American Gastroenterological Association (AGA) and the AGA Institute Clinical Guideline Committee. The researchers provide a patient summary to aid in better evidence-based shared decision-making.

Per the AGA guidelines, symptoms of chronic diarrhea include: an urgent need to use the bathroom, cramping, loss of control of bowel movements, nausea or upset stomach, stomach pain, dehydration, and malabsorption. Additional symptoms for diarrhea caused by infection may include bloody stools, fever and chills, light-headedness or dizziness, and vomiting.

Before making a diagnosis of IBS-D, physicians can consider finding the root cause of chronic diarrhea. Laboratory evaluations can include tests for giardia, celiac disease or gluten sensitivity, bile acid diarrhea, and fecal calprotectin or lactoferrin. A colonoscopy may also be needed, depending on symptom severity.

Related Articles

Specific symptoms of IBS-D include frequent instances of loose stool, an urgent need to move the bowels, cramps or stomach pain, gas, and stomach bloating.

IBS can be managed through diet, stress management, and medication therapy.


Smalley W, Falck-Ytter C, Carrasco-Labra A, Wani S, Lytvyn L, Falck-Ytter Y. AGA guidelines on the laboratory evaluation of functional diarrhea and diarrhea-predominant irritable bowel syndrome in adults (IBS-D): patient summary [published online July 29, 2019]. Gastroenterology. doi: 10.1053/j.gastro.2019.07.053