There are many probable causes of chronic diarrhea and abdominal pain including Inflammatory Bowel Disease (IBD), Irritable Bowel Syndrome (IBS), Celiac Disease, infectious GI pathogens, and malignancy. After excluding other causes of chronic diarrhea, a physician is left with the diagnosis IBS-diarrhea (IBS-D). One main cause of IBS-D is bile acid malabsorption.

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BILE ACIDS, IBS, AND 7AC4

Bile acids are synthesized from cholesterol in the liver and released into the digestive tract where they function to emulsify dietary fats and facilitate lipid absorption in the small intestine. More than 95% of bile acids are then reabsorbed primarily by active uptake in the distal ileum, while less than 5% are excreted in stool.

Patients with increased bile acids in their stool often suffer from chronic diarrhea, a condition called bile acid malabsorption (BAM). Approximately 25–30% of patients with IBS-D have BAM.1 Identifying patients with BAM is typically done by measuring total and fractionated bile acids in stool.

The loss of bile acids in the stool of patients with BAM leads to upregulation of bile acid synthesis in the liver. Recent studies have shown that serum concentrations of the metabolic intermediate in bile acid synthesis, 7ɑ-hydroxy-4-cholesten-3-one (7AC4) are elevated in patients with BAM and can be used as a surrogate to the timed fecal collection.2-4

BILE ACID MALABSORPTIONA Convenient Serum Test for a Common Cause of Chronic Diarrhea

Life Cycle of Bile Acids

REFERENCES

1. Aziz I, Mumtaz S, Bholah H, et al. High prevalence of idiopathic bile acid diarrhea among patients with diarrhea-predominant irritable bowel syndrome based on rome iii criteria. Clin Gastroenterol Hepatol 2015;13:1650–5 e2.

2. Vijayvargiya P, Camilleri M, Shin A, et al: Methods for diagnosis of bile acid malabsorption in clinical practice. Clin Gastroenterol Hepatol 2013;11(10):1232-1239

3. Camilleri M, Nadeau A, Tremaine WJ, et al: Measurement of Serum 7 Alpha-hydroxy-4-cholesten-3-one (or 7AC4), a Surrogate test for bile acid malabsorption in health, ileal disease and irritable bowel syndrome using liquid chromatography-tandem mass spectrometry. Neurogastroenterol Motil 2009;21(7):734-743

4. Wong BS, Camilleri M, Carlson P, et al: Increased bile acid biosynthesis is associated with irritable bowel syndrome with diarrhea. Clin Gastroenterol Hepatol 2012 Sep;10(9):1009-1015.e3

A UNIQUE TESTING APPROACH

Mayo Clinic physicians and researchers pioneered the understanding of BAM in chronic diarrhea. Mayo Medical Laboratories offers the first, stand-alone serum screening test for BAM.

Using the results of the Mayo Clinic 7AC4 test, the physician may rule out bile acid malabsorption, consider a confirmatory fecal test, or consider a trial treatment of a bile acid sequestrant.

WHICH TEST SHOULD I ORDER?} 7AC4, Bile Acid Synthesis, Serum (Mayo ID: 7AC4)

LABORATORY EVALUATION OF A PATIENT WITH CHRONIC DIARRHEA

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CLINICALLY ACTIONABLE RESULTS

The results of this test provide physicians with a clear understanding of the likelihood of bile acid malabsorption. Using this information, physicians can make informed treatment decisions for their patients.

Patient with chronic diarrhea without

occult blood

Symptoms meetRome IV criteria

Rule out non-IBS-D conditions

Evaluate for BAM

Next Steps

} Depending on the 7AC4 result BAM is unlikely Order confirmatory fecal bile acid test Start bile acid sequestrant therapy

Test Options

} 7AC4 Screening for BAM Fasting Serum Sample

} Fecal Bile Acids Definitive for BAM Requires 48h fecal collec-

tion while on a high fat diet

Sample report data