Recent developments in diagnosing bile acid diarrhea

INTRODUCTION

Bile acid diarrhea (BAD) commonly causes chronic diarrhea. Symptoms may be mistaken for disorders of gut brain interaction. Due to the lack of widely available diagnostic tests and poor recognition of BAD, there is a delay in diagnosis leading to increased healthcare system burden and decreased patient quality of life.

AREAS COVERED

A thorough review of the literature was conducted using PubMed for articles on the biological functions of bile acids, pathophysiology and management of BAD, but focusing on diagnostic testing including 75SeHCAT retention, 7αC4, FGF-19, fecal bile acids, and single stool tests. This narrative review discusses available modalities focusing on noninvasive stool and serum testing that are more widely available and show good sensitivity and specificity for diagnosis of BAD. 75SeHCAT retention is not available in many countries. Alternative diagnostic tests include total and primary fecal bile acid (BA) excretion in 48-hour collection or a single stool sample, serum7αC4 >46 or 52.5 ng/mL, and combination of single stool and serum 7αC4 ±watery stools (Bristol Stool Form Scale 6-7).

EXPERT OPINION

Given the ease of serum and single stool sample acquisition and diagnostic advances, clinical practice should embrace positive diagnosis, rather than BAS therapeutic trial. BAD needs to be considered in diverse gastrointestinal diseases.

Bile Acid Diarrhea in Adults and Adolescents

BACKGROUND

Bile acids are central to enterohepatic signaling pathways activated through natural receptors, farnesoid X receptor [FXR mediates synthesis of fibroblast growth factor-19 (FGF-19)], and G protein-coupled bile acid receptor 1 (GPBAR1, also known as TGR5). Although bile acid diarrhea (BAD) is more commonly encountered in ileal resection or disease, there is evidence documenting "idiopathic" BAD in about 20% of adolescents and 30% of adults presenting with chronic, non-bloody diarrhea often attributed to irritable bowel syndrome. Mechanism(s) leading to increased hepatic synthesis and colonic bile acid levels in "idiopathic" BAD include reduced synthesis of FGF-19 by the ileal mucosa, or genetic variation in hepatocyte proteins klotho β and FGF receptor 4 (FGFR4) that mediate negative feedback of bile acid synthesis.

PURPOSE

The objective of this review is to summarize the diagnosis of BAD in adults and adolescents. In addition to ⁷⁵ SeHCAT retention for diagnosis of BAD, studies have validated fasting serum 7αC4 and FGF-19, respectively, by-product and inhibitor of hepatic bile acid synthesis, as well as fecal bile acid measurements. These assays are widely available through reference laboratories, and they are being simplified (eg, measurement of primary fecal bile acids in a random stool sample). BAD has also been identified as a co-factor contributing to persistent diarrhea in other diseases in remission including inflammatory bowel disease, microscopic colitis, celiac disease, and neuroendocrine tumors. In summary, advances in diagnosis of BAD provide opportunities for generalists and pediatric and adult gastroenterologists to provide targeted treatment for BAD presenting as chronic non-bloody diarrhea.

Prevalence of biliary acid malabsorption in patients with chronic diarrhoea of functional characteristics: a prospective study

Background

Bile acid malabsorption occurs in up to one third of patients with chronic diarrhoea of functional characteristics. The gold standard test for its diagnosis is the ⁷⁵Selenium homocholic acid taurine (⁷⁵SeHCAT) test. The aim of this work is to confirm previous data suggesting that bile acid malabsorption, diagnosed by ⁷⁵Se-HCAT test, is the underlying cause of diarrhoea in a significant proportion of patients previously diagnosed with a functional disorder. In addition, we have analysed the clinical response of bile acid sequestrants in those patients with a bile acid diarrhoea diagnosis.

Methods

This is a prospective, single-centre study including consecutive adult patients diagnosed with chronic diarrhoea of unknown origin and with functional characteristics; systematic rule out of common causes of chronic diarrhoea was performed before bile acid malabsorption evaluation by ⁷⁵SeHCAT scanning. A retention percentage less than 10% was considered positive. Clinical response to cholestyramine was further evaluated in those patients with a positive diagnosis of bile acid diarrhoea

Results

38 patients (20 male, mean age 37.5 years) were finally included. Twenty (52.6%) patients included had a positive ⁷⁵SeHCAT test. Median body mass index was significantly higher in those patients. We did not find significant differences in other clinical or biochemical variables ⁷⁵SeHCAT-positive and ⁷⁵SeHCAT-negative groups. Only 6 of 17 (35.3%) patients responded to cholestyramine treatment; 10 patients did not have response or withdraw the drug due to adverse events. Logistic regression analysis showed that none of the included variables was a predictor of clinical response to cholestyramine.

Conclusions

Bile acid malabsorption occurs in a high proportion of patients suffering from chronic diarrhoea with functional characteristics. Systematic investigation of bile acid malabsorption should be included in the diagnostic algorithms of patients with chronic watery diarrhoea in the routine clinical practice. Absence of response to cholestyramine does not rule out bile acid diarrhoea.

High prevalence of primary bile acid diarrhoea in patients with functional diarrhoea and irritable bowel syndrome-diarrhoea, based on Rome III and Rome IV criteria

BACKGROUND

A high prevalence of primary bile acid diarrhoea (BAD) has been reported for Rome III defined irritable bowel syndrome (IBS)-diarrhoea and functional diarrhoea. We determined whether this still applies under the contemporaneous Rome IV criteria, given that the latter characterises IBS-diarrhoea as having more frequent abdominal pain compared with previous iterations, whilst no longer recognising abdominal discomfort.

METHODS

Patients referred for a 75SeHCAT test completed a baseline questionnaire comprising, i) demographic data, ii) risk factors for BAD (inflammatory bowel disease, bowel resection, cholecystectomy, microscopic colitis, celiac disease, abdominal-pelvic radiotherapy), iii) the Rome III and IV bowel disorder questionnaire, and iv) mood and somatisation scores. A diagnosis of BAD constituted a 75SeHCAT of ≤15%, with moderate to severe disease being defined as ≤10% and ≤5%, respectively.

FINDINGS

Of 300 patients with complete dataset, 184 had no risk factors for BAD and fulfilled criteria for either IBS-diarrhoea or functional diarrhoea. The prevalence of primary BAD was 38% (n = 70/184), with almost half having moderate (n = 16) to severe (n = 17) disease. Using the Rome III criteria, the prevalence of primary BAD was 36% in IBS-diarrhoea (n = 63/173) and 64% (n = 7/11) in functional diarrhoea; p = 0.11. Using the Rome IV criteria, the prevalence of primary BAD was 38% (n = 53/139) in IBS-diarrhoea and 38% (n = 17/45) in functional diarrhoea; p = 0.97. Patients with primary BAD experienced more frequent loose stools (p = 0.01) and had a higher body mass index (p<0.0001) compared to those without BAD, but otherwise no significant differences were seen in age, gender, mood, somatisation, or abdominal pain. The presence of primary BAD in patients classified as overweight or obese was approximately 40% and 60%, respectively.

INTERPRETATION

Over a third of patients with Rome IV IBS-diarrhoea or functional diarrhoea have primary BAD, similar to Rome III. We therefore recommend that, in secondary care settings, generic testing for primary BAD should be considered in patients presenting with chronic diarrhoea of presumed functional origin regardless of concomitant abdominal pain. Centres that lack tests for primary BAD, and who empirically treat instead, may consider targeting patients who are overweight or obese.

Differences in Fecal Microbiomes and Metabolomes of People With vs Without Irritable Bowel Syndrome and Bile Acid Malabsorption

BACKGROUND & AIMS

Irritable bowel syndrome (IBS) is a heterogeneous disorder, but diagnoses and determination of subtypes are made based on symptoms. We profiled the fecal microbiomes of patients with and without IBS to identify biomarkers of this disorder.

METHODS

We collected fecal and urine samples from 80 patients with IBS (Rome IV criteria; 16-70 years old) and 65 matched individuals without IBS (control individuals), along with anthropometric, medical, and dietary information. Shotgun and 16S ribosomal RNA amplicon sequencing were performed on feces, whereas urine and fecal metabolites were analyzed by gas chromatography and liquid chromatography-mass spectrometry. Co-occurrence networks were generated based on significant Spearman correlations between data. Bile acid malabsorption (BAM) was identified in patients with diarrhea by retention of radiolabeled selenium-75 homocholic acid taurine.

RESULTS

Patients with IBS had significant differences in network connections between diet and fecal microbiomes compared with control individuals; these were accompanied by differences in fecal metabolomes. We did not find significant differences in fecal microbiota composition among patients with different IBS symptom subtypes. Fecal metabolome profiles could discriminate patients with IBS from control individuals. Urine metabolomes also differed significantly between patients with IBS and control individuals, but most discriminatory metabolites were related to diet or medications. Fecal metabolomes, but not microbiomes, could distinguish patients with IBS with vs those without BAM.

CONCLUSIONS

Despite the heterogeneity of IBS, patients have significant differences in urine and fecal metabolomes and fecal microbiome vs control individuals, independent of symptom-based subtypes of IBS. Fecal metabolome analysis can be used to distinguish patients with IBS with vs those without BAM. These findings might be used for developing microbe-based treatments for these disorders.

Canadian Association of Gastroenterology Clinical Practice Guideline on the Management of Bile Acid Diarrhea

BACKGROUND & AIMS

Chronic diarrhea affects about 5% of the population overall. Altered bile acid metabolism is a common but frequently undiagnosed cause.

METHODS

We performed a systematic search of publication databases for studies of assessment and management of bile acid diarrhea (BAD). The certainty (quality) of evidence and strength of recommendations were rated according to the Grading of Recommendation Assessment, Development and Evaluation approach. Patient population, intervention, comparator, and outcome questions were developed through an iterative process and were voted on by a group of specialists.

RESULTS

The certainty of evidence was generally rated as very low. Therefore, 16 of 17 recommendations are conditional. In patients with chronic diarrhea, consideration of risk factors (terminal ileal resection, cholecystectomy, or abdominal radiotherapy), but not additional symptoms, was recommended for identification of patients with possible BAD. The group suggested testing using ⁷⁵selenium homocholic acid taurine (where available) or 7α-hydroxy-4-cholesten-3-one, including patients with irritable bowel syndrome with diarrhea, functional diarrhea, and Crohn's disease without inflammation. Testing was suggested over empiric bile acid sequestrant therapy (BAST). Once remediable causes are managed, the group suggested cholestyramine as initial therapy, with alternate BAST when tolerability is an issue. The group suggested against BAST for patients with extensive ileal Crohn's disease or resection and suggested alternative antidiarrheal agents if BAST is not tolerated. Maintenance BAST should be given at the lowest effective dose, with a trial of intermittent, on-demand administration, concurrent medication review, and reinvestigation for patients whose symptoms persist despite BAST.

CONCLUSIONS

Based on a systematic review, BAD should be considered for patients with chronic diarrhea. For patients with positive results from tests for BAD, a trial of BAST, initially with cholestyramine, is suggested.

Canadian Association of Gastroenterology Clinical Practice Guideline on the Management of Bile Acid Diarrhea

Background and Aims

Chronic diarrhea affects about 5% of the population overall. Altered bile acid metabolism is a common but frequently undiagnosed cause.

Methods

We performed a systematic search of publication databases for studies of assessment and management of bile acid diarrhea (BAD). The certainty (quality) of evidence and strength of recommendations were rated according to the Grading of Recommendation Assessment, Development and Evaluation approach. Patient population, intervention, comparator and outcome questions were developed through an iterative process and were voted on by a group of specialists.

Results

The certainty of evidence was generally rated as very low. Therefore, 16 of 17 recommendations are conditional. In patients with chronic diarrhea, consideration of risk factors (terminal ileal resection, cholecystectomy or abdominal radiotherapy), but not additional symptoms, was recommended for identification of patients with possible BAD. The group suggested testing using ⁷⁵selenium homocholic acid taurine (where available) or 7α-hydroxy-4-cholesten-3-one, including patients with irritable bowel syndrome with diarrhea, functional diarrhea and Crohn's disease without inflammation. Testing was suggested over empiric bile acid sequestrant therapy (BAST). Once remediable causes are managed, the group suggested cholestyramine as initial therapy, with alternate BAST when tolerability is an issue. The group suggested against BAST for patients with extensive ileal Crohn's disease or resection and suggested alternative antidiarrheal agents if BAST is not tolerated. Maintenance BAST should be given at the lowest effective dose, with a trial of intermittent, on-demand administration, concurrent medication review and reinvestigation for patients whose symptoms persist despite BAST.

Conclusions

Based on a systematic review, BAD should be considered for patients with chronic diarrhea. For patients with positive results from tests for BAD, a trial of BAST, initially with cholestyramine, is suggested.

The efficacy of a low-fat diet to manage the symptoms of bile acid malabsorption - outcomes in patients previously treated for cancer

Dietary fat ingestion triggers bile secretion into the gastrointestinal tract. Bile acid malabsorption affects >1% of the population, causing loose stool and other gastrointestinal symptoms. The diagnosis is frequently missed. Treatments are often considered ineffective. We evaluated low-fat diets for managing gastrointestinal symptoms in these patients. All patients reporting type 6 or 7 stool were offered a selenium-75 homocholic acid taurine (SeHCAT) scan. Prospective data in patients with 7-day scan retention <20% were analysed. -Patients requiring a bile acid sequestrant were given this before receiving dietary advice. Patients completed a 7-day food diary before dietetic consultations. Personalised dietary interventions, providing 20% of daily energy from fat, were prescribed. Symptoms were assessed using a modified gastrointestinal symptom rating scale questionnaire before and 4-12 weeks after dietary intervention. A total of 114 patients (49 male, median age 64 years, median body mass index 27 kg/m2) were evaluated. 44% of these patients were taking colesevelam. After dietary intervention, there was statistically significant improvement in abdominal pain and nocturnal defecation (0.2% alpha, p=0.001). Improvement in bowel frequency, urgency, flatulence, belching, borborygmi and stool consistency were seen, but did not reach statistical significance (p≤0.004-0.031). Dietary intervention is an effective treatment option for patients with symptomatic bile acid malabsorption and should be routinely considered.

Management of bile acid malabsorption using low-fat dietary interventions: a useful strategy applicable to some patients with diarrhoea-predominant irritable bowel syndrome?

This study evaluates the efficacy of low-fat dietary interventions in the management of gastrointestinal (GI) symptoms due to bile acid malabsorption. In total, 40 patients with GI symptoms and a 7-day (75)selenium homocholic acid taurine (SeHCAT) scan result of <20%, were prospectively recruited and then advised regarding a low-fat dietary intervention. Before and after dietary intervention, patients rated their GI symptoms using a 10-point numerical scale, and recorded their intake in 7-day dietary diaries. After dietary intervention, the median scores for all GI symptoms decreased, with a significant reduction for urgency, bloating, lack of control, bowel frequency (p ≥: 0.01). Mean dietary fat intake reduced to 42 g fat after intervention (p ≥: 0.01). Low-fat dietary interventions in patients with a SeHCAT scan result of <20% leads to clinically important improvement in GI symptoms and should be widely used.

Are bile acid malabsorption and bile acid diarrhoea important causes of loose stool complicating cancer therapy?

AIM

Gastrointestinal (GI) symptoms during and after cancer therapy can significantly affect quality of life and interfere with treatment. This study assessed whether bile acid malabsorption (BAM) or bile acid diarrhoea (BAD) are important causes of diarrhoea associated with cancer treatment.

METHOD

A retrospective analysis was carried out of consecutive patients assessed for BAM using ((75) Se) Selenium homocholic acid taurocholate (SeHCAT) scanning, after reporting any episodes of loose stool, attending a gastroenterology clinic in a cancer centre.

RESULTS

Between 2009 and 2013, 506 consecutive patients (54.5% male; age range: 20-91 years), were scanned. BAM/BAD was diagnosed in 215 (42.5%). It was mild in 25.6%, moderate in 29.3% and severe in 45.1%. Pelvic chemoradiation had induced BAM in > 50% of patients. BAM was also frequent after treatment for conditions not previously associated with BAM, such as anal and colorectal cancer, and was present in > 75% of patients referred after pancreatic surgery. It was also unexpectedly frequent in patients who were treated for malignancy outside the GI tract, such as breast cancer and haematological malignancy.

CONCLUSION

BAM/BAD are very common and under-appreciated causes of GI symptoms after cancer treatment. Health professionals should have a low threshold in suspecting this condition, as diagnosis and treatment can significantly improve quality of life.

Quantifying bile acid malabsorption helps predict response and tailor sequestrant therapy

Although recognised as a cause of chronic diarrhoea for over forty years, diagnostic tests and treatments for bile acid malabsorption (BAM) remain controversial. Recent National Institute for Health and Care Excellence (NICE) guidelines highlighted the lack of evidence in the field, and called for further research. This retrospective study explores the BAM subtype and severity, the use and response to bile acid sequestrants (BAS) and the prevalence of abnormal colonic histology. 264 selenium-75-labelled homocholic acid conjugated taurine (SeHCAT)-tested patient records were reviewed and the severity and subtype of BAM, presence of colonic histopathology and response to BAS were recorded. 53% of patients tested had BAM, with type-2 BAM in 45% of patients with presumed irritable bowel syndrome. Colonic histological abnormalities were similar overall between patients with (29%) or without (23%) BAM (p = 0.46) and between BAM subtypes, with no significant presence of inflammatory changes. 63% of patients with BAM had a successful BAS response which showed a trend to decreased response with reduced severity. Colestyramine was unsuccessful in 44% (38/87) and 45% of these (17/38) were related to medication intolerance, despite a positive SeHCAT. 47% (7/15) of colestyramine failures had a successful colesevelam response. No patient reported colesevelam intolerance. Quantifying severity of BAM appears to be useful in predicting BAS response. Colesevelam was better tolerated than colestyramine and showed some efficacy in colestyramine failures. Colestyramine failure should not be used to exclude BAM. Colonic histology is of no relevance.

Methods for diagnosis of bile acid malabsorption in clinical practice

Altered concentrations of bile acid (BA) in the colon can cause diarrhea or constipation. More than 25% of patients with irritable bowel syndrome with diarrhea or chronic diarrhea in Western countries have BA malabsorption (BAM). As BAM is increasingly recognized, proper diagnostic methods are needed to help direct the most effective course of treatment for the chronic bowel dysfunction. We review the methodologies, advantages, and disadvantages of tools that directly measure BAM: the (14)C-glycocholate breath and stool test, the (75)selenium homotaurocholic acid test (SeHCAT), and measurements of 7 α-hydroxy-4-cholesten-3-one (C4) and fecal BAs. The (14)C-glycocholate test is laborious and no longer widely used. The (75)SeHCAT has been validated but is not available in the United States. Measurement of serum C4 is a simple and accurate method that can be used for most patients but requires further clinical validation. Assays to quantify fecal BA (total and individual levels) are technically cumbersome and not widely available. Regrettably, none of these tests are routinely available in the United States; assessment of the therapeutic effects of a BA binder is used as a surrogate for diagnosis of BAM. Recent data indicate the advantages to studying fecal excretion of individual BAs and their role in BAM; these could support the use of the fecal BA assay, compared with other tests. Measurement of fecal BA levels could become a routine addition to the measurement of fecal fat in patients with unexplained diarrhea. Availability ultimately determines whether the C4, SeHCAT, or fecal BA test is used; more widespread availability of such tests would enhance clinical management of these patients.

Managing bile acid diarrhoea

Bowel symptoms including diarrhoea can be produced when excess bile acids (BA) are present in the colon. This condition, known as bile acid or bile salt malabsorption, has been under recognized, as the best diagnostic method, the (75)Se-homocholic acid taurine (SeHCAT) test, is not available in many countries and is not fully utilized in others. Reduced SeHCAT retention establishes that this is a complication of many other gastrointestinal diseases. Repeated studies show SeHCAT tests are abnormal in about 30% of patients otherwise diagnosed as diarrhoea-predominant irritable bowel syndrome or functional diarrhoea, with an estimated population prevalence of around 1%. Recent work suggests that the condition previously called idiopathic bile acid malabsorption (BAM) is not in fact due to a defect in absorption, but results from an overproduction of BA because of defective feedback inhibition of hepatic bile acid synthesis, a function of the ileal hormone fibroblast growth factor 19 (FGF19). The approach to treatment currently depends on binding excess BA, to reduce their secretory actions, using colestyramine, colestipol and, most recently, colesevelam. Colesevelam has a number of potential advantages that merit further investigation in trials directed at patients with bile acid diarrhoea.