Colonoscopy and SeHCAT for investigation of chronic diarrhea

Misinterpreting Diarrhea-Predominant Irritable Bowel Syndrome and Functional Diarrhea: Pathophysiological Highlights

Irritable bowel syndrome with predominant diarrhea (IBS-D) and functional diarrhea (FD) are disorders of gut-brain interaction characterized by recurring symptoms which have a serious impact on the patient's quality of life. Their pathophysiology is far from being completely understood. In IBS-D growing evidence suggests that bile acid malabsorption (BAM) could be present in up to 30% of patients. Microscopic colitis (MC) is a well-known cause of watery diarrhea and some patients, at first, can be diagnosed as IBS-D or FD. Both BAM and MC are often responsible for the lack of response to conventional treatments in patients labelled as "refractory". Moreover, because BAM and MC are not mutually exclusive, and can be found in the same patient, they should always be considered in the diagnostic workout when a specific treatment for BAM or MC is unsatisfactory. In the present review the possible shared pathogenetic mechanisms between BAM and MC are discussed highlighting how MC can induce a secondary BAM. Moreover, a brief overview of the current literature regarding the prevalence of their association is provided.

Irritable bowel syndrome: Epidemiology, overlap disorders, pathophysiology and treatment

Irritable bowel syndrome (IBS) is a common chronic gastrointestinal disease with a significant impact on patients' quality of life and a high socioeconomic burden. And the understanding of IBS has changed since the release of the Rome IV diagnosis in 2016. With the upcoming Rome V revision, it is necessary to review the results of IBS research in recent years. In this review of IBS, we can highlight future concerns by reviewing the results of IBS research on epidemiology, overlap disorders, pathophysiology, and treatment over the past decade and summarizing the latest research.

Biomarkers for bile acid diarrhoea in functional bowel disorder with diarrhoea: a systematic review and meta-analysis

There is no universally available laboratory test to diagnose bile acid diarrhoea (BAD).

OBJECTIVE

To conduct a systematic review and meta-analysis to identify a biomarker for idiopathic BAD in patients with functional bowel disorder (FBD) with diarrhoea.

DESIGN

We searched multiple databases through 15 May 2015. Data were only available to estimate the diagnostic yield of each test (the prevalence of a positive test). Estimates were pooled across studies using the random effects model.

RESULTS

We included 36 studies, enrolling 5028 patients (24 using ⁷⁵selenium homotaurocholic acid test (⁷⁵SeHCAT) retention of <10%, 6 using fasting serum C4, 3 using fasting serum fibroblast growth factor 19 (FGF19) and 2 based on total faecal bile acid (BA) excretion over 48 h). The diagnostic yields (and 95% CI) of abnormal tests were: 0.308 (0.247 to 0.377) for ⁷⁵SeHCAT retention (<10%), 0.171 (0.134 to 0.217) for serum C4, 0.248 (0.147 to 0.385) for serum FGF19 and 0.255 (0.071 to 0.606) for total faecal BA excretion over 48 h. The majority of the analyses were associated with substantial heterogeneity. Performance characteristics relative to a gold standard test could not be estimated.

CONCLUSIONS

Overall, the test with the highest diagnostic yield conducted in the largest number of studies was ⁷⁵SeHCAT retention, which is not widely available in many countries outside Europe and Canada. Using different diagnostic tests, 25% (average) of patients with lower FBD with diarrhoea has evidence of idiopathic BAD. These tests serve to identify idiopathic BAD among patients with FBD with diarrhoea. Further studies are required to appraise the performance characteristics of tests for idiopathic BAD.

Are the definitions for chronic diarrhoea adequate? Evaluation of two different definitions in patients with chronic diarrhoea

BACKGROUND

The classical definition of chronic diarrhoea is ≥3 defecations/day, with a stool weight of more than 200 g and duration of ≥4 weeks. However, with this definition many patients with substantial symptoms and pathology will be excluded from further investigations. As a consequence other definitions have been proposed, mainly based on evaluation of the stool form.

OBJECTIVE

To evaluate the accuracy of the classic criteria for diarrhoea in comparison with a definition based on stool consistency, using the Bristol Stool Form Scale.

METHODS

All patients were investigated with laboratory tests, upper and lower gastrointestinal endoscopy with biopsies, and SeHCAT test. They were asked to complete a diary recording stool frequency and consistency during a week, as well as other gastrointestinal symptoms (pain, bloating and gas).

RESULTS

One hundred and thirty-nine subjects were eligible for analysis. Ninety-one had an organic cause of diarrhoea. Fifty-three patients had ≥3 loose stools/day, whereas 86 reported <3 stools/day. Ninety had a median stool consistency that was mushy or loose and 49 had harder stools. A higher proportion of subjects with an organic cause of their diarrhoea compared with subjects with a functional bowel disorder had ≥3 loose stools/day, 43/91 (47%) vs. 10/48 (21%) (p < 0.01). Similarly, more subjects with an organic cause of their diarrhoea versus patients with a functional bowel disorder had a median stool consistency that was mushy or watery, 73/91 (80%) vs. 17/48 (35%), p < 0.0001. When diarrhoea was defined according to stool form, more patients were classified correctly as having a functional disorder or organic disorder, compared with the classical definition (p < 0.05).

CONCLUSION

Loose stools defined according to the Bristol Stool Form scale seem to be the best predictor of having an organic cause of the diarrhoea.

Increased colonic bile acid exposure: a relevant factor for symptoms and treatment in IBS

OBJECTIVE

Bile acids may play a role in the pathogenesis of IBS. We investigated the potential effects of bile acids entering the colon and its role in the symptom pattern in IBS.

DESIGN

We measured 75Se-labelled homocholic acid-taurine (75SeHCAT) retention, and serum levels of 7α-hydroxy-4-cholesten-3-one (C4) and fibroblast growth factor (FGF) 19 in patients with IBS (n=141) and control subjects (75SeHCAT n=29; C4 and FGF19 n=435). In patients with IBS stool frequency and form, as well as GI symptom severity were registered, and in a proportion of patients colonic transit time and rectal sensitivity were measured (n=66). An 8-week open-label treatment with colestipol was offered to patients with 75SeHCAT <20%, and the effect of treatment was evaluated with IBS severity scoring system and adequate relief of IBS symptoms.

RESULTS

Compared with controls, patients with IBS had lower 75SeHCAT values (p=0.005), higher C4c levels (C4 corrected for cholesterol) (p<0.001), but similar FGF19 levels. Abnormal 75SeHCAT retention (<10%) was seen in 18% of patients, whereas 23% had elevated C4c levels. Patients with IBS with 75SeHCAT retention <10% had more frequent stools, accelerated colonic transit time, rectal hyposensitivity, a higher body mass index, higher C4c and lower FGF19 levels. Colestipol treatment improved IBS symptoms (IBS severity scoring system 220±109 vs. 277±106; p<0.01), and 15/27 patients fulfilled criteria for treatment response (adequate relief ≥50% of weeks 5-8).

CONCLUSIONS

Increased colonic bile acid exposure influences bowel habit and colonic transit time in patients with IBS. A high response rate to open label treatment with colestipol supports this, but placebo-controlled studies are warranted.

Bile acid malabsorption in chronic diarrhea: pathophysiology and treatment

BACKGROUND

Bile acid malabsorption (BAM) is a common but frequently under-recognized cause of chronic diarrhea, with an estimated prevalence of 4% to 5%.

METHODS

The published literature for the period 1965 to 2012 was examined for articles regarding the pathophysiology and treatment of BAM to provide an overview of the management of BAM in gastroenterology practice.

RESULTS

BAM is classified as type 1 (secondary to ileal dysfunction), type 2 (idiopathic) or type 3 (secondary to gastrointestinal disorders not associated with ileal dysfunction). The estimated prevalence of BAM is >90% in patients with resected Crohn disease (CD) and 11% to 52% of unresected CD patients (type 1); 33% in diarrhea-predominant irritable bowel syndrome (type 2); and is a frequent finding postcholecystectomy or postvagotomy (type 3). Investigations include BAM fecal bile acid assay, 23-seleno-25-homo-tauro-cholic acid (SeHCAT) testing and high-performance liquid chromatography of serum 7-α-OH-4-cholesten-3-one (C4), to determine the level of bile acid synthesis. A less time-consuming and expensive alternative in practice is an empirical trial of the bile acid sequestering agent cholestyramine. An estimated 70% to 96% of chronic diarrhea patients with BAM respond to short-course cholestyramine. Adverse effects include constipation, nausea, borborygmi, flatulence, bloating and abdominal pain. Other bile acid sequestering agents, such as colestipol and colesevelam, are currently being investigated for the treatment of BAM-associated diarrhea.

CONCLUSIONS

BAM is a common cause of chronic diarrhea presenting in gastroenterology practice. In accordance with current guidelines, an empirical trial of a bile acid sequestering agent is warranted as part of the clinical workup to rule out BAM.

Randomised clinical trial: The ileal bile acid transporter inhibitor A3309 vs. placebo in patients with chronic idiopathic constipation--a double-blind study

BACKGROUND

One half of patients with constipation are not satisfied with available therapies, hence there is a need for more effective and well-tolerated drugs.

AIM

To evaluate the effects of a specific inhibitor of the Ileal Bile Acid Transporter (IBAT; syn apical sodium-dependent bile acid transporter; ASBT) in patients with chronic idiopathic constipation (CIC) with focus on safety, colonic transit and efficacy signals.

METHODS

This was a single-centre, prospective, randomised, double-blind, placebo-controlled study with a dose-escalating design in patients with CIC. In addition to evaluation of conventional safety and tolerability parameters, (i) colonic transit time (CTT) was measured using radio-opaque markers, (ii) metabolic parameters [lipid profile, C4 (7α-hydroxy-4-cholesten-3-one) and FGF19 (Fibroblast Growth Factor 19)] were evaluated, and (iii) constipation parameters, such as changes in stool frequency and consistency, were analysed.

RESULTS

Thirty patients were randomised into five dose-levels (range: 0.1-10 mg/day) or to placebo. All patients completed a 14-day treatment period, and the safety/tolerability analysis was favourable. A3309, present in picomolar concentrations in plasma, induced up to a three-fold increase in bile acid synthesis (C4) and a reduction of plasma FGF19, as well as reduction in total and LDL cholesterol. CTT was reduced in the highest dose groups; the main acceleration was identified in the left colon. Efficacy parameters showed trends for increased number of spontaneous bowel movements and improved stool consistency.

CONCLUSIONS

Ileal Bile Acid Transporter inhibition is a novel mechanism for treatment of patients with chronic idiopathic constipation and has additional benefits of improving metabolic parameters (EudraCT 2008-003255-72).

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.

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

BACKGROUND

Recurrent, watery diarrhoea affects one-third of patients diagnosed with irritable bowel syndrome ('IBS-D'). Idiopathic bile acid malabsorption ('I-BAM') may be the cause.

AIM

To determine the prevalence of I-BAM in patients suffering from IBS-D.

METHODS

A systematic search was performed of publications reporting patients presenting with IBS-D type symptoms, who were subsequently confirmed as having I-BAM by SeHCAT scanning.

RESULTS

Eighteen relevant studies, 15 prospective, comprising 1223 patients were identified. Five studies (429 patients) indicated that 10% (CI: 7-13) patients had severe bile acid malabsorption (SeHCAT 7 day retention <5% of baseline value). 17 studies (1073 patients) indicated that 32% (CI: 29-35) patients had moderate bile acid malabsorption (SeHCAT <10%). 7 studies (618 patients) indicated that 26% (CI: 23-30) patients had mild (SeHCAT <15%) bile acid malabsorption. Pooled data from 15 studies showed a dose-response relationship according to severity of malabsorption to treatment with a bile acid binder: response to colestyramine occurred in 96% of patients with <5% retention, 80% at <10% retention and 70% at <15% retention.

CONCLUSIONS

Idiopathic adult-onset bile acid malabsorption is not rare. International guidelines for the management of irritable bowel syndrome need to be revised so that clinicians become more aware of this possibility.

Review article: Small intestinal bacterial overgrowth, bile acid malabsorption and gluten intolerance as possible causes of chronic watery diarrhoea

BACKGROUND

Chronic watery diarrhoea is one of the most common symptoms prompting GI evaluation. Recently, new diagnostic considerations have emerged as possible factors in chronic diarrhoea.

AIM

To review available data regarding diagnosis and treatment of chronic diarrhoea with an emphasis on bacterial overgrowth and bile acid malabsorption.

METHODS

A systematic search of the English language literature of chronic diarrhoea was performed focused on three possible aetiologies of diarrhoea: small intestinal bacterial overgrowth (SIBO), idiopathic bile salt malabsorption (IBAM), gluten responsive enteropathy.

RESULTS

Recent studies suggest that SIBO and bile acid malabsorption may have been underestimated as possible causes of chronic watery diarrhoea. Gluten intolerance with negative coeliac serology is a contentious possible cause of watery diarrhoea, but requires further research before acceptance as an entity.

CONCLUSION

In patients with otherwise unexplained chronic watery diarrhoea, small intestinal bacterial overgrowth and bile salt malabsorption should be considered and investigated.

Efficient diagnosis of suspected functional bowel disorders

Functional bowel disorders (FBDs) are common disorders that are characterized by various combinations of abdominal pain and/or discomfort, bloating and changes in bowel habits. At present, diagnosing FBDs often incurs considerable health-care costs, partly because unnecessary investigations are performed. Patients are currently diagnosed as having an FBD on the basis of a combination of typical symptoms, normal physical examination and the absence of alarm features indicative of an organic gastrointestinal disease. Basic laboratory investigations, such as a complete blood count, measurement of the erythrocyte sedimentation rate and serological tests for celiac disease, are useful in the initial evaluation. No further investigations are needed for most patients who have typical symptoms and no alarm symptoms. The most important alarm symptoms include signs of gastrointestinal bleeding, symptom onset above 50 years of age, a family history of colorectal cancer, documented weight loss and nocturnal symptoms. The presence of alarm symptoms obviously does not exclude an FBD, but further investigation is needed before confirmation of the diagnosis. For patients with predominant and severe diarrhea, a more thorough diagnostic work-up should normally be considered, including colonoscopy with colonic biopsies and a test for bile-acid malabsorption.

Bile acid malabsorption

Patients with bile acid malabsorption typically present with chronic, watery diarrhea. Bile acids recirculate between the liver and small intestine in the enterohepatic circulation. They are reabsorbed in the distal small intestine, and normally only a small fraction of the bile acid pool is lost to the colon during each cycle. In patients with bile acid malabsorption, a larger amount of bile acids is spilled into the colon, where the acids stimulate electrolyte and water secretion, which results in loose to watery stools. The common causes of bile acid malabsorption are ileal resection and diseases of the terminal ileum (Crohn's disease and radiation enteritis), which result in a loss of bile acid transporters and, consequently, diminished reabsorption. Bile acid malabsorption also has been documented in a small group of patients with chronic, watery diarrhea who have no demonstrable ileal disease (idiopathic bile acid malabsorption). The amount of bile acid loss to the colon determines the clinical presentation. Patients with mild to moderate bile acid malabsorption present with watery diarrhea and generally respond very well to treatment (with abolishment of diarrhea) with bile acid binders such as cholestyramine. Patients with more severe bile acid malabsorption have both diarrhea and steatorrhea. Treatment with cholestyramine is of no benefit in this group of patients and may, in fact, worsen steatorrhea. These patients are best treated with a low-fat diet supplemented with medium-chain triglycerides.

Diagnostic yield of colonoscopy based on symptoms

OBJECTIVE

There are only a few data on the diagnostic yield of colonoscopy in different symptoms. The aim of this study was to assess the outcome of colonoscopy in patients with various gastrointestinal symptoms and to estimate the relation between the findings and the presenting symptoms.

MATERIAL AND METHODS

1121 consecutive colonoscopies were registered during 1 year. Asymptomatic subjects and patients with known inflammatory bowel disease (IBD) were excluded, leaving 767 eligible for the study. Symptoms, findings and clinical judgement about their relation were recorded.

RESULTS

In patients with bleeding symptoms (n=405), serious colonic pathology--cancers and adenomas >1 cm, IBD and angiodysplasia--was found in 54 (13.3%), 83 (20.5%) and 20 (4.9%) patients, respectively; 162 (40%) patients had findings that could be related to the symptom. In 173 subjects with non-bloody diarrhoea, the diagnostic yield was 31.2%, i.e. mostly IBD and microscopic colitis. In 189 subjects with other gastrointestinal symptoms, the diagnostic yield was 13.2%. Serious colonic pathology was found in 8 of 362 (2.2%) subjects examined because of non-bleeding symptoms.

CONCLUSION

The diagnostic yield of colonoscopy is high in patients with bleeding symptoms or diarrhoea, while the prevalence of significant findings is equal to a screening population in patients with other symptoms.

Mesalazine with or without cholestyramine in the treatment of microscopic colitis: randomized controlled trial

BACKGROUND

Collagenous colitis (CC) and lymphocytic colitis (LC) are chronic inflammatory diseases of the colon with a benign and sometimes relapsing course. Frequency among patients with chronic diarrhea and normal looking colonoscopy is around 10-15%. To date, treatment of CC and LC is not well defined. Data about these conditions are mostly derived from retrospective studies. The aim of the present study was to evaluate the response to treatment and the clinical course of CC and LC in a large group of patients prospectively diagnosed.

METHODS AND RESULTS

A total of 819 patients underwent a colonoscopy because of chronic watery diarrhea and among them we found 41 patients with LC and 23 with CC. These patients were later randomized and assigned to treatment with mesalazine or mesalazine + cholestyramine for 6 months. Fifty-four patients (84.37%) had resolved diarrhea in less than 2 weeks. After 6 months a colonoscopy with biopsies was repeated. Clinical and histological remission was achieved in 85.36% of patients with LC and in 91.3% with CC, with a better result in patients with CC treated with mesalazine + cholestyramine. During a mean period of 44.9 months, 13% of patients relapsed; four with LC and three with CC. They were retreated for another 6 months. At the end of this period one patient with CC was still symptomatic and persistence of CC was confirmed at histology.

CONCLUSIONS

Treatment with mesalazine seems to be an effective therapeutic option for LC to date, while mesalazine + cholestyramine seems to be more useful in the treatment of CC.