Inflammatory bowel disease

The term inflammatory bowel disease (IBD) describes clinical conditions with chronic, relapsing and remitting inflammation of the gastrointestinal (GI) tract. Crohn’s disease (CD) and ulcerative colitis (UC) are the two most common types of IBD, both of which are heterogeneous diseases at the clinical level.¹ They are chronic immune-mediated diseases characterised by a dysregulated immune response in genetically susceptible people.² UC is limited to the colon while CD can involve any part of the GI tract from the mouth to the anus. Age at diagnosis, location and extent of disease, and disease behaviour are major factors affecting disease course and prognosis.^3,4 IBD can be diagnosed at any age, with usual age of onset between 15 and 45 years.⁵

Risk factors for inflammatory bowel disease

The two most common risk factors associated with inflammatory bowel diseases are genetic predisposition (NOD2 or IL-10 gene mutation; Ashkenazi Jewish heritage) and smoking.¹ If two parents have CD, there is a 50% increased risk of their child developing the disease. For Ashkenazi Jews, there is 17% increased risk.

The recent increase in incidence⁶ and changes in disease risk occurring with migration^7,8 suggest environmental factors also play a role in the pathogenesis of IBD. One possible mechanism by which the environment influences disease risk may be via the gut microbiome.^2,9-14 This, together with the concordance reported in familial cases of IBD and in identical twins with IBD,^15,16 highlights that shared environmental and genetic factors appear to shape disease phenotypic presentation.

Other potential risk factors include vitamin deficiency, psychosocial stressors, early cessation of breastfeeding, caesarean birth, exposure to infection in early life and antibiotic use.

Prevalence of inflammatory bowel disease

Australia and New Zealand reportedly have the highest IBD incidence in the world: in 2005 around 61,000 Australians were living with IBD, comprising 28,000 people with CD and 33,000 with UC.⁵ An estimated 1,622 new cases are being diagnosed every year – by 2020, the number of people with CD is projected to increase by 20% to around 33,500, while the number with UC is projected to increase by 25% to over 41,000.⁵

Other high incidence areas include Northern Europe and North America. The occurrence of IBD is beginning to stabilise in high-incidence areas, however numbers are rising in low-incidence areas such as southern Europe, Asia and much of the developing world.

Sign and symptoms of inflammatory bowel disease

IBD symptoms depend on the location and amount of intestinal tract involved in the disease. Symptoms range from mild to severe during relapses, and may decrease or disappear entirely during remissions.

Typical symptoms include diarrhoea (with or without bleeding), abdominal pain, rectal bleeding, weight loss, nausea and vomiting. IBD patients also frequently suffer from chronic conditions affecting other organs.

There is no single diagnostic test that can reliably diagnose all cases of IBD and numerous tests may be required. In suspected IBD, tests distinguishing IBD from infectious gastroenteritis, irritable bowel syndrome (IBS) and coeliac disease are considered. Investigations also help in defining disease activity and severity.

• Crohn’s disease
• Ulcerative colitis

Adapted from Access Economics. The economic costs of Crohn’s disease and ulcerative colitis. 2007.⁵

Management of inflammatory bowel disease

A multidisciplinary approach is taken to the management of IBD, including input and care from gastroenterologists, colorectal surgeons, general practitioners, IBD nurses, radiologists, dietitians and psychologists. It is increasingly recognised that maintaining remission and anticipating problems, and thereby preventing complications, is an effective management strategy compared with managing acute disease episodes.

Adapted from Access Economics. The economic costs of Crohn’s disease and ulcerative colitis. 2007.⁵

Irritable bowel syndrome

Irritable bowel syndrome (IBS) is a chronic and relapsing functional gastrointestinal disorder (FGID) – FGIDs are considered ‘disorders of gut–brain interaction’.^1,2

In IBS recurrent abdominal pain is associated with defecation or a change in bowel habits.³ Disordered bowel habits are typically present (ie constipation, diarrhoea or a combination of both), together with symptoms of abdominal bloating/distention. Symptom onset should occur at least 6 months before diagnosis and symptoms should be present during the past 3 months.³

IBS is the most common of the FGIDs, affecting approximately 5–12% of the population in western countries.^3,4 It appears more complex than some other FGIDs, and may result from a combination of factors relating to motility, visceral hypersensitivity, mucosal immune dysregulation, alterations of bacterial flora, and central nervous system–enteric nervous system dysregulation.² IBS presently has no known underlying pathology. Importantly, a number of common comorbidities are often also present and require exclusion.

Symptoms of irritable bowel syndrome

IBS is classified primarily in terms of symptoms², which include abdominal bloating and excessive wind, abdominal distension and discomfort and altered bowel habits including bowel urgency, diarrhoea and constipation and a lack of satisfaction of stool emptying (ie “not all gone”). Arrival at a firm symptom-based diagnosis allows for reduced patient anxiety and also better management. However, exclusion of organic disease is a requirement.

The symptoms of IBS occur in the absence of any underlying pathology and present as a collection of symptoms that cluster as a syndrome.^1,2

Without a mechanism to explain its clinical features, understanding of IBS is informed by a biopsychosocial model that takes into account the interactions between physiology, psychology and environment.^1,2,5

A biopsychosocial model of functional gastrointestinal disorders

Adapted from Drossman 2016.²
Early life factors can influence psychosocial functioning, as well as their mutual interaction (via the brain-gut axis).
Together these factors inflluence the clinical presentation and clinical outcome of functional gastrointestinal disorders.
CNS, central nervous system; ENS, enteric nervous system.

Management of irritable bowel syndrome

Effective management of IBS commonly requires a multimodal approach including dietary, psychological and pharmacological interventions.^2,6 The integrated effects of altered physiology and psychosocial status will determine the illness experience and, ultimately, the clinical outcome. In turn, outcomes affect the severity of the disorder. Consequently, psychosocial factors are essential to understanding IBS and for the development of an effective treatment plan.⁵

While IBS symptoms are not life threatening, they can be embarrassing, interfere with activities of daily living and impair quality of life, as well as affect health care use with significant economic impacts.⁷

There are four IBS subgroups recognised:²

1. IBS with predominant constipation (IBS-C)
2. IBS with predominant diarrhoea (IBS-D)
3. IBS with mixed bowel habits (IBS-M) a syndrome of alternating diarrhoea and constipation
4. unclassified IBS (IBS-U)

Determining whether a patient has a diarrhoea-predominant or a constipation-predominant IBS will inform further management.

Irritable bowel syndrome and milk intake

Some IBS patients may have reduced lactose absorptive capacity and may find that their IBS symptoms improve when their intake of dairy products is limited. In most patients, lactose intolerance is not the complete answer and other food triggers should also be considered. As limiting milk and dairy intake can have long-term health consequences, including effects on bone health, any ongoing reduction of milk and dairy intake should be assessed and reviewed by a dietitian.

Irritable bowel syndrome and other dietary management

Monash University low-FODMAP diet

The Monash University low-FODMAP diet is an effective dietary treatment for managing IBS symptoms. In international studies, up to 86% of patients with IBS have achieved relief of overall gastrointestinal symptoms from the diet.^9,10 The low FODMAP diet has become a first-line dietary therapy for IBS and is recommended in the Therapeutic Guidelines for Gastroenterology.

A low FODMAP diet involves restricting foods that are rich in these short chain carbohydrates, under the guidance of a dietitian.

There are two phases of the low-FODMAP diet:

• Phase one: suspected FODMAP triggers are restricted from the diet for approximately 2–6 weeks to obtain symptom relief
• Phase two: the diet is broadened according to individual’s specific needs, informing diet choices for the longer term. In this phase, individual tolerance to FODMAP foods is determined in order to expand the diet. Patients with IBS differ in both the type and amount of FODMAP foods that they can tolerate before symptoms develop. This step is important as low-FODMAP dietary trials suggest a potential negative effect of dietary FODMAP exclusion if it is maintained for too long, primarily due to alterations in the microbiome with a reduction in potentially beneficial bifidobacteria.

The Monash University low FODMAP Diet app for Android and iPhone is the first evidence-based smartphone application for practitioners and patients following the low-FODMAP diet and should be used in conjunction with dietetic advice.

The app provides detailed resources on the avoidance of foods high in symptom-causing fermentable carbohydrates, including suitable alternatives to ensure the diet is nutritionally adequate, to aid compliance and optimal symptom management.

Probiotics

There is insufficient good evidence to recommend a specific probiotic product. However, if a probiotic helps an individual it should achieve this within a few weeks. Probiotic supplementation may be ceased if no improvement occurs after this time. However, once a probiotic is stopped, the provided probiotic bacterial strain(s) will gradually cease to colonise the gut or reduce in numbers (so, the exogenous probiotic effects only last as long as the supplementation continues).

Psychosocial approaches

Gut-directed hypnotherapy and cognitive behavioural therapy have been shown to benefit patients with IBS.⁶ A psychologist specialising in gastrointestinal disorders with training in hypnotherapy can provide guidance to patients.

Coeliac disease

Coeliac disease is an immune-mediated chronic inflammatory disease caused by the ingestion of gluten-containing grains (eg wheat, rye and barley).¹ It predominantly affects the gastrointestinal (GI) tract but can have widespread symptoms.¹ Once considered a rare disease, improved clinical awareness and testing have contributed to its current recognition as a common lifelong disorder that can occur at any age, with a prevalence of 0.5–1.0% in Caucasian populations.^1,2

Clinical symptoms associated with GI inflammation commonly include malabsorption, abdominal pain, constipation and diarrhoea. Other clinical features include coeliac disease antibodies (primarily tissue transglutaminase 2 IgA antibodies and endomysium IgA antibodies) and variable degrees of small intestinal mucosal damage, identifiable by biopsy.¹

Risk factors for coeliac disease

Coeliac disease has a strong genetic basis – there is a high degree of disease concordance (~75%) in monozygotic (identical) twins compared with dizygotic twins,^1,3,4 and its prevalence is 10–15% higher among people who have a first-degree relative with the condition.⁵ Coeliac disease is strongly associated with the human leukocyte antigen (HLA) genetic variants HLA DQ2.5 and HLA DQ8 and, despite regional variation, the correlation is generally ≥95%.^1,4 Other less common genetic polymorphisms (eg HLA DQ2.2) account for the remaining small minority.¹

HLA-based determination to identify genetic susceptibility to coeliac disease has become routine,¹ however these genetic variants are found in 25–30% of most Caucasian populations despite the majority of individuals not expressing the disease phenotypically. The main role of HLA determination is thus to safely exclude coeliac disease, especially in patients already consuming a gluten-free diets.¹

Signs and symptoms of coeliac disease

A considerable proportion of patients with coeliac disease have either no symptoms or subclinical symptoms (such as tiredness or irritability). Recognising the symptom pattern of coeliac disease will inform the need for further testing.¹

Testing for coeliac disease

Testing for coeliac disease, except HLA genotyping, should be done while patients are on a sufficient gluten-containing diet providing about 3–6 g gluten/day (eg 2–4 pieces of wheat-based bread/day). If not, a sufficient gluten-containing diet needs to be eaten for 4–6 weeks before any testing can be performed.

If the patient is reluctant or unable to consume a sufficient gluten-containing diet, then a coeliac disease gene test (ie HLA-DQ2/8 testing) can be performed to safely exclude coeliac disease. Remember, a positive HLA-DQ2/8 gene test is not diagnostic on its own: if it is positive, a 4–6 week challenge with a diet containing sufficient gluten will be required.^1,8

After 4–6 weeks of exposure to a sufficient gluten containing diet, coeliac disease serology can then be requested. This includes tissue transglutaminase 2-IgA (tTG2-IgA) with deamidated gliadin peptide-IgG (PGD-IgG) OR tissue transglutaminase 2-IgA (tTG-IgA) with total IgA (to exclude the 2–3% of people with coeliac disease who are IgA deficient.^1,4

Coeliac-specific serological tests now rival the accuracy of biopsy tests in many circumstances.¹ However, biopsies remain an essential part of coeliac disease diagnosis in the vast majority of patients, even though duodenal biopsies might be avoided in a small minority of patients when specific serological, HLA and clinical criteria are met.^1,4

Interpreting test results

If tTG2-IgA OR DGP-IgG is positive, then refer to a gastroenterologist to confirm coeliac disease with a small intestinal biopsy. If serology is negative but your patient is symptomatic and positive for HLA-DQ2 and/or HLA-DQ8, then consider referral to a gastroenterologist for further testing.⁹

Coeliac Australia has a range of resources to support general practitioners and other health professionals, including a Diagnosing coeliac disease fact sheet.

Management of coeliac disease

Long-term and strict compliance with the gluten-free diet is the only known management and is essential.¹⁰ Failure to adhere to a strict gluten-free diet can increase the risk of osteoporosis, poor growth, infertility, miscarriage, nutrient deficiencies including iron deficiency, gastrointestinal tumours (by 2-fold) and mortality (by 2-fold). Motivating benefits to patients for maintaining compliance include improved wellbeing, vitality and mental function.^8,10

Coeliac disease and milk digestion
The lactase enzyme, which breaks down the milk sugar lactose, is produced in the epithelial cells lining the small intestine. Patients diagnosed with coeliac disease may develop a temporary or secondary lactose intolerance, likely due to damage to the lining of the small intestine, which then disrupts lactase production.¹¹ However, most people with coeliac disease often tolerate lactose in their diet after around 3 months’ compliance with a coeliac (gluten-free) diet.

Patient information is available from the Gastroenterological Society of Australia (information about lactose intolerance/lactase deficiency) and Coeliac Australia (information about lactose intolerance).