Systematic review: the prevalence of idiopathic bile acid malabsorption as diagnosed by SeHCAT scanning in patients with diarrhoea-predominant irritable bowel syndrome

Defining primary bile acid diarrhea: making the diagnosis and recognizing the disorder

Chronic diarrhea due to bile acid malabsorption may be considered as contributing to the diagnosis when it results from secondary causes, such as ileal resection affecting the enterohepatic circulation. However, the primary form (also known as idiopathic bile acid malabsorption) is not well recognized as a common condition and patients are left undiagnosed. Primary bile acid diarrhea can be diagnosed by the nuclear medicine 75Se-homocholyltaurine (SeHCAT) test, although this is unavailable or underutilized in many settings. A systematic review suggests that approximately 30% of patients who would otherwise be diagnosed with diarrhea-predominant irritable bowel syndrome or functional diarrhea have abnormal SeHCAT retention. Serum 7α-hydroxy-4-cholesten-3-one can also be measured to show increased bile acid synthesis. The reasons for the lack of recognition of primary bile acid diarrhea are discussed, and these are compared with the other common cause of malabsorption, celiac disease. The lack of a clear pathophysiological mechanism has been a problem, but recent evidence suggests that impaired feedback control of hepatic bile acid synthesis by the ileal hormone FGF19 results in overproduction of bile acids. The identification of FGF19 as the central mechanism opens up new areas for development in the diagnosis and treatment of primary bile acid diarrhea.

Missing link identified: GpBAR1 is a neuronal bile acid receptor

In addition to their classical functions in aiding the digestion and absorption of lipids, bile acids are increasingly gaining appreciation for their roles in regulating intestinal physiology. Bile acids are now widely considered as hormones that exert a wide range of physiological and pathophysiological effects both within and outside the gastrointestinal (GI) tract. The discovery of the bile acid receptor, GpBAR1, represented a major step forward in our understanding of how cells can sense and respond to bile acids. GpBAR1 is a cell surface G protein-coupled receptor expressed on adipose tissue and skeletal muscle where it has been found to be an important regulator of cellular metabolism. In a paper published in the current issue of Neurogastroenterology and Motility, Poole et al. investigated the expression and function of GpBAR1 in mouse intestine. They found the receptor to be expressed throughout the GI tract but predominantly on nerves within the myenteric and submucosal plexuses. Employing in vitro and in vivo techniques they demonstrated that activation of GpBAR1 by bile acids inhibits small and large intestinal motor function and delays intestinal transit. The effects of GpBAR1 activation are mediated through activation of cholinergic and nitrergic interneurons. The data reported by Poole et al. provides novel and exciting insights into how bile acids exert their actions in the intestine. This Editorial Viewpoint aims to further consider the potential physiological and pathophysiological implications of their findings.

Effectiveness and tolerability of colesevelam hydrochloride for bile-acid malabsorption in patients with cancer: a retrospective chart review and patient questionnaire

BACKGROUND

Commercially available bile-acid sequestrants are not well tolerated by >80% of patients.

OBJECTIVE

The aim of the present study was to assess the effectiveness and tolerability of colesevelam hydrochloride in patients who developed bile-acid malabsorption after cancer therapy.

METHODS

The present study comprised 2 parts: a retrospective chart review of the electronic patient records and a patient questionnaire assessing outcome measures. All patients included in this study had a diagnosis of cancer and were being followed up in a cancer clinic at The Royal Marsden Hospital. In addition, all had symptoms of bile-acid malabsorption for >3 months and had been prescribed colesevelam in the gastroenterology clinic at the hospital. The electronic records of patients who were prescribed colesevelam between 2004 and 2007 were obtained from the hospital pharmacy. Those patients who were prescribed colesevelam and did not take any of the prescribed medication or did not return for a follow-up clinical review were excluded. To help further assess outcomes, a questionnaire was mailed to patients who were still residing in the United Kingdom, were not terminally ill, and were not lost to follow-up. The questionnaire comprised questions that assessed medication history (ie, whether patients were still taking colesevelam or not [and the reason for not taking colesevelam]), dosage, effectiveness for symptom relief, and adverse events.

RESULTS

In total, 45 patients (37 women and 8 men; median age, 58 years [range, 32-89 years]) who received treatment with colesevelam between 2004 and 2007 were included. Of these, 36 were sent a questionnaire and 30 responded. Identifiable causes of bile acid malabsorption in this sample population were pelvic radiotherapy (n = 29), small-bowel resection (12), upper gastrointestinal surgery (2), high-dose chemotherapy (1), and new-onset Crohn's disease (1). Of these patients, 67% (30/45) had not previously responded to cholestyramine treatment, but following treatment with colesevelam, this group had a recorded improvement in: diarrhea, 83% (25/30); urgency of defecation, 74% (20/27); frequency of defecation, 72% (21/29); steatorrhea, 71% (12/17); abdominal pain, 68% (15/22); and fecal incontinence, 62% (13/21). Based on the medical chart review and the patient questionnaire, after colesevelam treatment, the following proportions of all 45 patients studied experienced improvement in symptoms: loose stool (diarrhea), 88% (medical chart) and 80% (questionnaire); frequency of defecation, 77% and 83%, respectively; steatorrhea, 76% and 80%; urgency of defecation, 76% and 80%; abdominal pain, 74% and 58%; and fecal incontinence, 69% and 74%. During the study period, 15 patients discontinued colesevelam: ineffectiveness, 5; adverse events, 5 (because >or=1 of the following: bloating, constipation, heartburn, abdominal pain, flatulence, or perianal soreness); and other reasons, 7 (too many tablets or tablets difficult to swallow [3]; symptoms resolved [2]; colesevelam replaced with another medication [1]; and lost to follow-up [1]). Sixty-seven percent (30/45) of patients continued using colesevelam for up to 4 years.

CONCLUSION

In view of the data found in this retrospective chart review and patient questionnaire, prospective, double-blind, placebo-controlled trials of colesevelam for bile acid malabsorption are warranted.

A physiological approach to modernize the management of cancer chemotherapy-induced gastrointestinal toxicity

PURPOSE OF REVIEW

Gastrointestinal toxicity during chemotherapy is frequent. Symptomatic therapies for gastrointestinal toxicity, which do not address the underlying cause, may result in inadequate symptom control. With advances in curative treatment regimens, it becomes more important to minimize treatment toxicity which otherwise may compromise optimal chemotherapy and the chance of cure.

RECENT FINDINGS

For decades, oncologists have concentrated on delineating the pathological processes, which occur within the gastrointestinal tract during chemotherapy treatment. However, pathological change does not in itself cause symptoms. Symptoms only arise when physiological functions are altered. In immunosuppressed patients, it is a priority to exclude infection as a cause for symptoms. In the presence of diarrhoea, the best investigative paradigm for this is stool culture, upper gastrointestinal endoscopy with duodenal biopsies and duodenal aspirate combined with flexible sigmoidoscopy and left colonic biopsies. Once infection has been excluded, although large studies have not been performed, case series repeatedly suggest that gastrointestinal symptoms arising during cancer chemotherapy can often be cured if newly acquired, gastrointestinal physiological deficits are identified.

SUMMARY

Although many physiological changes induced by chemotherapy may be relatively transient and settle weeks or months after the end of treatment, during chemotherapy, their manifestations can be protean and severe. A systematic failure to research the frequency with which physiological causes of the symptoms are amenable to treatment has denied many patients' logical therapies for their chemotherapy-induced symptoms, and as a result, it is likely that symptomatic treatments are frequently suboptimal.

Bile acid malabsoption: a forgotten diagnosis?

Bile acid malabsorption (BAM) is never life threatening but can cause chronic symptoms. A survey of senior British gastroenterologists was conducted to examine their approach to patients with potential BAM. Of the 706 gastroenterologists contacted, 62% replied. Gastroenterologists see on average 500 new patients in clinic annually; 34% have chronic diarrhoea and 1% are diagnosed with BAM. In those with chronic diarrhoea, 6% of gastroenterologists investigate for BAM first line, while 61% consider the diagnosis only in selected patients or not at all. Sixty-one per cent of patients are diagnosed with type 1 BAM (secondary to terminal ileal disease), 22% have type 2 (idiopathic bile acid malabsorption) and 15% type 3 (unrelated to terminal ileal disease). Only one third of gastroenterologists use a definitive diagnostic test for BAM. BAM (particularly type 2) is under-diagnosed because it is frequently not considered and even when considered, many patients are not subjected to definitive diagnostic testing.

Effects of chenodeoxycholate and a bile acid sequestrant, colesevelam, on intestinal transit and bowel function

BACKGROUND & AIMS

Di-alpha hydroxy bile salt, sodium chenodeoxycholate (CDC), and bile acid binding have unclear effects on colonic transit in health and disease.

METHODS

We performed 2 randomized, double-blind, placebo-controlled studies. In healthy volunteers (20 per group), we evaluated the effects of oral placebo, 500 mg, or 1000 mg of CDC (delayed-release, each given for 4 days) on gastrointestinal and colonic transit. A second trial compared the effects of colesevelam (1.875 g, twice daily) versus placebo in 24 patients (12 per group) with diarrhea-predominant irritable bowel syndrome (IBS-D) on transit, daily bowel frequency and consistency, and colonic mucosal permeability. Serum fasting 7alpha-hydroxy-4-cholesten-3-one (7alphaC4) was measured to screen for bile acid malabsorption. Effects of treatments on transit were compared using analysis of covariance with body mass index and 7alphaC4 as covariates.

RESULTS

In healthy volunteers, CDC significantly accelerated colonic transit (at 24 and 48 hours, P = .01 and P < .0001, respectively), increased stool frequency and ease of passage (both P < .001), and evacuation (P = .02), and decreased stool consistency (P < .001). Four of the 24 IBS-D patients had increased serum 7alphaC4 levels. In IBS-D, colesevelam modestly affected overall colonic transit (24 h; P = .22). Emptying of the ascending colon took an average of 4 hours longer in patients given colesevelam compared with placebo; treatment effect was associated with baseline serum 7alphaC4 levels (P = .0025). Colesevelam was associated with greater ease of stool passage (P = .048) and somewhat firmer stool consistency (P = .12). No effects on mucosal permeability or safety were identified.

CONCLUSIONS

Sodium chenodeoxycholate in health and colesevelam in IBS-D patients have opposite effects on colonic transit and fecal parameters.

Recent advances in the understanding of bile acid malabsorption

INTRODUCTION

Bile acid malabsorption (BAM) is a syndrome of chronic watery diarrhoea with excess faecal bile acids. Disruption of the enterohepatic circulation of bile acids following surgical resection is a common cause of BAM. The condition is easily diagnosed by the selenium homocholic acid taurine (SeHCAT) test and responds to bile acid sequestrants. Idiopathic BAM (IBAM, primary bile acid diarrhoea) is the condition where no definitive cause for low SeHCAT retention can be identified.

SOURCES OF DATA

Review of PubMed and major journals.

AREAS OF AGREEMENT

Evidence is accumulating that BAM is more prevalent than first thought. Management of chronic diarrhoea involves excluding secondary causes. Treatment of the condition is with bile acid binders.

AREAS OF CONTROVERSY

SeHCAT testing is not widely performed, limiting awareness of how common this condition can be. The underlying mechanism for IBAM has been unclear.

GROWING POINTS

Increasing awareness of the condition is important. Alternative mechanisms of IBAM have been suggested which involve an increased bile acid pool size and reduced negative feedback regulation of bile acid synthesis by FGF19. New sequestrants are available.

AREAS TIMELY FOR DEVELOPING RESEARCH

Further research into the precise mechanism of IBAM is needed. Improvements in the recognition of the condition and optimization of treatment are required.