Issue 133 bile acid malabsorption

CONDITIONS & DISORDERS

BILE ACID MALABSORPTION Rebecca Gasche Registered Dietitian, Countess of Chester Hospital NHS Trust Rebecca has a keen interest and specialises in gastroenterology dietetics. She currently works in the community setting in the Chester area, running clinics and group sessions to manage a wide range of gastroenterology conditions.

This article will focus on a specific type of malabsorption - bile acid malabsorption (BAM) - with the aim of raising awareness of the signs and symptoms, to improve recognition and early diagnosis.

Malabsorption is a word we often come across when working in a clinical setting.

It can be defined as the poor absorption of nutrients in the small intestine and may be nutrient specific (i.e. affecting only the absorption of fats), or generalised (i.e. affecting the absorption of many nutrients).1 There are a number of causes for malabsorption, such as intestinal resections, mucosal damage, pancreatic insufficiency, inflammatory bowel disease or coeliac disease.1 WHAT IS BILE ACID MALABSORPTION?

REFERENCES REFERENCES For full article Please visit references the Subscriber please zone at NHDmag.com CLICK HERE . . .

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Bile contains bile acids, which are manufactured in the liver and stored in the gallbladder. The ingestion of dietary fat causes the gallbladder to contract and the bile acids are secreted into the upper small bowel to aid the breaking down and absorbing of fats and vitamins.

They are then reabsorbed in the terminal ileum, and around 97% of bile acids are recycled for re-use back to the liver (the last 3% are excreted in faeces), a process called enterohepatic circulation.2 If the terminal ileum is diseased or has been resected, or if hepatic bile production is increased so much so that it overwhelms normal absorptive mechanisms, excess bile can enter the colon and cause erratic, chronic diarrhoea.3 BAM is best diagnosed by a SeHCAT test or by the 7ɑ-hydroxy-4-cholesten3-one blood test.3 The SeHCAT test involves the patient swallowing a capsule containing a synthetic bile salt with a small amount of ionising radiation, which tests the function of the bowel by measuring how well the compound is retained or lost in the

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body.2 The SeHCAT test involves two scans one week apart to assess the amount of the compound retained, and results will be as follows: • retention values of 10-15% (mild bile acid malabsorption) • retention values of 5-10% (moderate bile acid malabsorption) • retention values of 0-5% (severe bile acid malabsorption)2 The SeHCAT test is advised in the British Society of Gastroenterology (BSG) guidelines.4 BAM is thought to affect one in 100 people5 and, unfortunately, is often misdiagnosed, with physicians frequently misdiagnosing patients with irritable bowel syndrome.3 BAM can be effectively treated with medications and dietary changes.

SYMPTOMS

The main symptom of BAM is diarrhoea,5 which can be classed as bile acid diarrhoea (BAD).6 BAD is caused as the excess bile acids are not absorbed from the ileum, but are passed into the large intestine. This excess of bile acids irritates the lining of the large intestine and stimulates electrolyte and water secretion, causing urgent diarrhoea.5 As well as inducing secretion of sodium and water, BAD is also caused by various mechanisms including, increasing colonic motility, stimulating defecation, inducing mucus secretion and damaging the mucosa, which increases mucosal permeability.2 BAD can often be described as chronic, watery diarrhoea. Diarrhoea is

CONDITIONS & DISORDERS

. . . BAM patients can suffer from a wide range of other gastrointestinal symptoms, including abdominal bloating, incontinence, excess wind, lethargy and abdominal cramping.

defined as the abnormal passage of loose or liquid stools more than three times daily, or a volume of stool greater than 200g/day and to be classed as chronic diarrhoea, it must persist for more than four weeks.2 The diarrhoea may often be in the form of steatorrhea (pale, greasy and hard to flush away), and be frequent, with patients reporting up to 10 episodes of diarrhoea during the day and at times nocturnally.

A recent study by Bannaga et al6 looked at patient-reported symptoms and outcomes of those suffering from BAM, in particular how BAD can affect a patient’s quality of life. A questionnaire was collected anonymously by BAM Support UK (a charity set up in 2015)7 and the Bile Salt Malabsorption Facebook group8 and concluded that 91% of patients with BAM reported symptoms of BAD. 44% of the participants reported that they had been experiencing symptoms of BAD for five years prior to diagnosis and, unfortunately, just over half of the cohort felt as though their symptoms had been dismissed during clinical consultations. 28% felt their GPs were unaware of BAD. As well as diarrhoea, BAM patients can suffer from a wide range of other gastrointestinal symptoms,9 including abdominal bloating, incontinence, excess wind, lethargy and abdominal cramping.5,6 CAUSES

BAM can be divided into three types depending on aetiology: Type 1: where the terminal ileum (where bile acids are absorbed) has been affected.

This could be due to removal, resection or inflammation of the ileum, as a result of surgery due to conditions such as Crohn’s disease (a condition which affects the whole digestive tract and causes inflammation), or cancer treatment.

Type 2: primary idiopathic malabsorption - which has no known cause. In people with type 2 bile acid malabsorption, there is a history of diarrhoea that can be either continuous or intermittent.

Type 3: associated with cholecystectomy, peptic ulcer surgery, chronic pancreatitis, coeliac disease, diabetes mellitus, radiotherapy or small bowel bacteria overgrowth.2,5 TREATMENT

The treatment for BAM usually involves medications and if the BAM is caused by an underlying condition, for example small bowel bacteria overgrowth, treatment of this can in turn improve symptoms. The medications used are called bile acid sequestrants, which bind to the bile in the small intestine, before they pass through to large intestine, therefore preventing the irritation of the large bowel which can lead to diarrhoea.5 The most common medications used to treat BAM are: • colestyramine and colestipol • colesevelam Colestyramine and colestipol are in powdered form and are often used as firstline medical treatment. However, the tolerance of these medications is fairly low, as they are not very palatable. The dose must be adjusted for each patient, as too high a dose may cause constipation.5 Colesevelam is a newer drug and is available in tablet form, so is, therefore, often used if the powdered alternatives are not tolerated. www.NHDmag.com April 2018 - Issue 133

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Table 1: Recommended fat intakes for BAM patients Recommended daily calorie intake

Recommended total fat (grams)

Total recommended fat intake as a % of RDI

Low fat (grams)

Total fat intake for a low fat diet as a% of RDI

Women

2000

65

30%

40

20%

Men

2500

75

30%

50

20%

BAM Support UK: http://bamsupportuk.org/a-low-fat-diet.html

The NICE guidance for colesevelam and BAM concluded that colesevelam appears to be well tolerated, but does carry adverse effects in some patients, such as flatulence and constipation.10 The guidance also discusses a randomised controlled trial (RCT) which reported no improvement in outcomes with colesevelam in 24 women with diarrhoeapredominant irritable bowel syndrome, four of whom had evidence of BAM. However, the study may have been underpowered to detect any differences between the groups.10 Further evidence shows that the use of colesevelam for bile acid malabsorption reported in two small case series found that colesevelam improved diarrhoea and gastrointestinal symptoms in people with BAM.10 The study earlier mentioned by Bannaga et al reported that following treatment, usually with bile acid sequestrants, 60% of participants reported improvement of diarrhoea and most reported their mental health had been positively impacted.6 Patients have been known to report symptoms of embarrassment, depression, isolation and low self-esteem as a result of BAM,6 and guidance emphasises how BAM can have a considerable impact of lifestyle and quality of life.2 DIETARY INTERVENTION

Once BAM has been confirmed, the patient should be referred to a dietitian to discuss a low fat diet.5 The use of a low fat diet to improve symptoms of BAD is reported to be largely unknown,11 despite studies suggesting its importance.12,13 A recent study conducted

by Watson et al concluded that the use of low fat dietary interventions in patients with BAM led to a clinically important improvement in GI symptoms and, therefore, should be widely used.11 In this particular study, dietary fat was 24

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restricted by one third to a median of 39.1g per day.11 Generally, it is advised that a low fat diet is <40g per day5,7 for women (see Table 1).

Further research, conducted in 2017 by Jackson et al, also supports the use of a low fat diet to treat BAM/BAD, demonstrating that there was a significant reduction in urgency, flatulence, abdominal pain, nocturnal defaecation, belching and borborygmi upon following a low fat diet, as well as improvement in stool consistency and frequency. The study goes onto say that the exact fat restriction for effectiveness requires further study.9 Other dietary measures which may be useful and were noted to have been used in patients in the research conducted by Bannaga et al, include elimination diets to identify specific food triggers, for example lactose-free, low-FODMAP and low-residue diets.9 BAM Support UK7 describes dietary intervention as not being a ‘one size fits all’ process, and highlights that dietary changes may be different for different people. It discusses the use of low fat diets and potential food triggers, such as gluten and dairy. It is emphasised that the advice on their page is not written by a dietitian or nutritionist. However, when looking at the current evidence, the advice it provides is accurate.

CONCLUSION

BAM is a common form of malabsorption, with its symptoms of BAD having a severe impact on a patient’s quality of life. Early recognition and treatment needs to be improved, as patients are often misdiagnosed, and increasing awareness with all healthcare professionals can help. Treatment includes the use of bile acid sequestrants and dietary support to guide patients through a low fat diet and help to identify specific food triggers may also be used.