Functional problems and their medical management

Introduction

Symptoms related to functional gastrointestinal disorders (FGIDs) are highly prevalent. In community-based studies, up to 22% of ‘normal’ UK subjects can be diagnosed as having irritable bowel syndrome (IBS) and up to 28% have functional constipation. These disorders are constellations of symptoms – they are not diseases. As such, the emphasis of management of these patients is based on simple principles: the exclusion of organic disease, making a confident diagnosis, explaining why symptoms occur, alteration of lifestyle where appropriate and avoidance of surgery. Education about healthy lifestyle behaviours, reassurance that the symptoms are not due to a life-threatening disease such as cancer and establishment of a therapeutic relationship are essential, and patients have a greater expectation of benefit from lifestyle modification than drugs. This chapter will deal primarily with IBS and functional constipation, leaving the treatment of faecal incontinence to Chapter 13 . Similarly, rectal prolapse, which is a frequent co-morbidity of chronic constipation, is dealt with in Chapter 14 .

The prevalence of functional disorders depends on the exact diagnostic criteria used; the current standards are the Rome IV criteria. These have updated the previous core diagnostic criteria for IBS: namely the presence of abdominal pain, altered bowel function (in terms of altered stool form or frequency) and a temporal relationship between pain and function. The new criteria require ‘pain’ rather than just ‘discomfort’ and that the pain is present at least once a week. The definition of functional constipation requires the presence of at least two of the following: less than three bowel actions a week, need to strain or manually assist evacuation on >25% of occasions, passage of hard stools on >25% of occasions or a sensation of abnormal evacuation on >25% of occasions. These symptoms need to be chronic, and organic disease needs to have been excluded. Although these criteria can be criticised for being over-inclusive, what is clear is that FGIDs represent a major burden on secondary and tertiary outpatient clinics and IBS is the commonest diagnosis in gastrointestinal clinics. An important confounding factor to be borne in mind when reviewing the literature on FGIDs is that the overwhelming majority of studies originate from tertiary centres. Patients attending such institutions are known to have disproportionately high scores on scales of depression, health-related anxiety and somatisation, representing a potentially biased, self-selected group. One further exacerbating variable in assessing studies of FGIDs is that there is a notoriously high placebo response, ranging from 30–80%.

Irritable bowel syndrome

The key to successful management of IBS is empathic reassurance. This will need to be individually directed according to the patient’s symptoms, beliefs and anxieties. Early and positive diagnosis is essential. Helpful factors in establishing a diagnosis are: (i) presence of symptoms for more than 6 months; (ii) frequent consultations for non-gastrointestinal symptoms; (iii) self-report that stress aggravates symptoms.

A key component of the reassurance is provision of a simple explanation of the benign nature and prognosis of the condition. Patients should be advised that no more than 2% of patients need their diagnosis of IBS to be revised at 30 years of follow-up. Equally, it is important to remember that 88% of patients had recurring episodes of gastrointestinal symptoms, and so reassurance should be allied to advice about the need for long-term symptom control.

Investigation

The presence of alarm features such as symptom onset after age 50 years, rectal bleeding, significant weight loss or abdominal mass mandates serological and luminal investigation to exclude organic disease. Investigations in these frequently young patients (the majority of patients at presentation are aged less than 35 years ) should otherwise be avoided since they may both exacerbate patients’ anxieties and undermine their confidence in the clinician. The search for a simple diagnostic test of IBS remains, and faecal calprotectin has emerged as a possible candidate to differentiate IBS from an organic cause of diarrhoea. The three hallmark features of IBS are:

Abdominal pain (not just discomfort)
Altered bowel pattern (constipation or diarrhoea or both)
Temporal relationship between pain and altered bowel function

An important diagnosis to consider, especially in the presence of low-grade anaemia, is coeliac disease.
Microscopic colitis should be a differential diagnosis in an older patient with diarrhoea (especially if nocturnal), weight loss and a history of autoimmune disease and recent commencement of a non-steroidal or proton-pump inhibitor.

Approximately 5% of patients fulfilling IBS diagnostic criteria will have histological evidence of coeliac disease compared to 0.5% of controls without IBS symptoms, 13% have reduced faecal elastase, suggestive of pancreatic exocrine insufficiency, and 28% have bile acid malabsorption.

Treatment

A stepwise approach to care is advocated, recognising that many patients with mild symptoms, and even some with more severe ones, will respond to such an approach.

Lifestyle modification

The low FODMAPs diet has emerged in a series of randomised clinical trials as an effective treatment for patients with IBS, especially for the symptoms of bloating, flatulence and abdominal discomfort. Careful dietary adherence supported by specialised dietitians appears to be vital for the success of the diet. Long-term data with the low FODMAPs diet are not available and strict FODMAP restriction is associated with inadequate nutrient intake (e.g., calcium) and potential alteration of gut microbiota. Another helpful dietary intervention worth considering in diarrhoea-predominant IBS patients (d-IBS) is reduction of excess caffeine and sorbitol (found in chewing gum and sweeteners).

Studies have been carried out on the effect of dietary fibre augmentation in some constipation-predominant IBS (c-IBS) patients. ^, Early placebo-controlled cross-over studies showed some acceleration of transit but no significant effect on symptoms. Later studies have corroborated the absence of beneficial effect on symptoms and suggested that there is an increase in abdominal bloating, discomfort and flatulence during dietary fibre supplementation. In summary, the effect of dietary fibre in IBS is not significantly beneficial, and the diet is frequently difficult to adhere to in the long term. Current guidelines generally recommend avoiding fibre supplementation in IBS patients ( www.nice.org/uk/CG061 ).

Pharmacological treatments

Most patients with FGIDs do not need regular drug therapy. The strongest evidence for a single agent in IBS patients is in d-IBS, where loperamide is a well-tolerated and effective treatment of diarrhoea and urgency.

The popular aetiological theory that IBS symptoms relate to gut spasm has led to a huge number of uniformly low-quality studies of anti-spasmodics in IBS patients. These have been subject to meta-analysis. In essence, what can be concluded is that, even allowing for publication bias in favour of positive studies, the evidence is of only modest benefit for anti-cholinergic (such as dicycloverine, hyoscine) or anti-spasmodic drugs (mebeverine, peppermint) over placebo in treating the symptoms of IBS.

In contrast, the data for the efficacy of tricyclic anti-depressants show unequivocal benefit in favour of low-dose usage of these agents. Doses of amitriptyline or nortriptyline of 10–50 mg act at both the central (anxiety and depression) and peripheral (neuromodulatory) mechanisms of IBS.

The putative mechanisms of action of tricyclic agents are through an effect on gut serotonin receptors and visceral sensitivity.

Many drugs that agonise or antagonise serotonin receptors have been developed, and the effect of all these drugs amounts to about 20% advantage over placebo.

There is good evidence supporting the use of ondansetron for d-IBS. Serotonin agents are amongst a number of emerging agents targeting enteric neurotransmitter receptors, some of which may have a role in relieving the sensory symptoms of IBS. In contrast to studies of low-dose tricyclics, standard doses of newer anti-depressants (selective serotonin re-uptake inhibitors) lead to a less impressive improvement in IBS, and at greater cost. ^, Linaclotide is licensed for use in patients with constipation-predominant IBS. Finally, early evidence suggests the possibility that some probiotic strains of bacteria may have a beneficial influence in patients with IBS, though this is very much emerging information.

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