Diagnosis And Treatment Of Irritable Bowel Syndrome

Introduction

Irritable Bowel Syndrome (IBS) is a common gastrointestinal disorder that is estimated to affect 1 in every 10 people globally, however, the prevalence varies greatly between countries.¹ This article will discuss the disease in greater detail, how it is diagnosed and its treatment options.

What is IBS?

IBS belongs to a group of conditions known as Functional Gastrointestinal Disorders (FGIDs) which are chronic disorders of the gut-brain interaction, which give rise to several symptoms, without any biochemical or structural abnormalities to account for them.² Common symptoms of IBS include gastrointestinal pain (often relieved following defecation), distension of the abdomen, bloating, constipation, lumpy/hard stools, diarrhoea, frequent stools, and mucus in stools.³

The variation in symptoms speaks to the pathogenesis of the condition, as IBS is thought to encompass several diseases with their unique pathologies, which present in similar ways.⁴ Patients can be classified further based on the IBS symptoms they present with: IBS with constipation, IBS with diarrhoea, or mixed-stool-pattern IBS, which applies to people who present with both constipation and diarrhoea.⁵

How is IBS diagnosed?

The symptoms form the first half of the diagnostic assessment for IBS; the other part is the Rome IV criteria.⁶ The original Rome guidelines for IBS were published in 1989, and have been revised several times since then.⁷ The current iteration - Rome IV, was released in 2016 and has eliminated the term ‘discomfort’ from the diagnostic criteria, as this term can have different meanings in different languages and thus be difficult to interpret for many patients.⁸

Instead, the criteria now require abdominal pain to be present for at least 1 day a week, for the previous 3 months before examination.⁹ Furthermore, the pain experienced must be associated with 2 of the following 3 criteria: 

• Pain can increase about defecation¹⁰
• Pain is associated with a change in the frequency of stool
• Pain is associated with a change in the form (appearance) of stool

As mentioned previously, IBS can be classified into 3 types based on an individual’s bowel habits and when using the Rome IV criteria, the assessment is made based only on the stools formed during days with abnormal bowel movement.¹¹ This informs the classification of the IBS subtypes, which also makes use of the Bristol School Form Scale (BSFS), which is a scale used to categorise stools from 1 to 7, with 1 describing hard, lumpy stools, and 7 describing watery diarrhoea.¹² The Rome IV IBS subtypes, informed by the BSFS are as follows:

• IBS-C (predominant constipation) - where >25% of bowel movements are between BSFS types 1-2 and <25% between types 6-7
• IBS-D (predominant diarrhoea) - where >25% of bowel movements are between BSFS types 6-7 and <25% are between types 1-2
• IBS-M (mixed bowel habits) - where >25% of bowel movements are between BSFS types 1-2 and >25% are between types 6-7
• IBS-U (unclassified IBS) - where patients meet the diagnostic criteria for IBS but their bowel habits cannot be categorised into any of the above subtypes

However, symptom-based criteria are not solely sufficient for an IBS diagnosis, as further testing must be performed to exclude the possibility that another disease causes IBS-like symptoms.¹³ For example, if patients over 40 present with IBS-like symptoms, they should also be screened for colon cancer, as for this age demographic, there is an increased risk of incidence compared to the rest of the population, and significant overlap between diagnostic groups.¹⁴ 

A patient's history should also be sought to eliminate the possibility of IBS misdiagnosis, as previous medical experiences can highlight potential non-IBS sources of the current symptoms.¹³ Furthermore, IBS is a biopsychosocial disorder, meaning that psychological illnesses, stresses or traumas can lead to a manifestation and/or exacerbation of symptoms.¹⁵

Therefore, clinicians should incorporate a psychological evaluation within their patient history to determine whether there have been any past or ongoing events that may be contributing to the symptoms experienced, which may make it easier to treat the condition through psychiatric help going forward.¹⁶

A physical examination should also be performed to rule out any structural abnormalities that may account for the symptoms, such as abnormalities in the anal and rectal region, pelvic floor dysfunction, weight loss and fever.¹⁷ IBS patients often present with tenderness in the left lower abdomen and discomfort during a digital rectal exam, however, this observation is not sufficient nor specific enough to determine an IBS diagnosis.¹⁸ 

Treatment options for IBS

The range of symptoms on display and the various subtypes of IBS mean that the treatment plan should be adjusted based on each individual. In the following section, treatment options for each subtype will be examined.

Medication

For individuals with IBS-C symptoms, the laxative lubiprostone has been found to improve overall symptoms including stool form and frequency, abdominal pain, and bloating.¹⁹ The selective serotonin reuptake inhibitor (SSRI), also known as an antidepressant -Fluoxetine has been shown to relieve bloating and improve stool frequency and consistency in IBS-C patients.²⁰

IBS-D patients benefit from a different set of medications, one such being amitriptyline, which is a tricyclic antidepressant that has been shown to improve overall symptoms including feelings of incomplete evacuation and stool form.²¹ The antibiotic Rifaximin is effective in reducing bloating, as a short-course treatment in IBS-D patients.²²

For both IBS-D and IBS-M intramuscular injections of the synthetic analogue for somatostatin-octreotide, have been found to improve stool consistency, but not overall symptoms.²³

Lifestyle and Diet Changes

Aside from medication, there are several changes to an individual’s lifestyle and diet that they can adopt, which may aid in relieving their IBS symptoms. Similarly to the efficacy of medication, the effectiveness of each change can depend on the subtype of IBS.

When it comes to lifestyle, factors such as exercise, sleep and exposure to stress can dramatically affect the symptoms of IBS.²⁴ Research has indicated that exercises such as walking, aerobics and yoga, are effective in treating IBS.²⁵ Furthermore, research has shown that poorer sleeping habits are more frequently observed in those with IBS symptoms, than in the general population, which suggests that remedying one’s sleeping patterns may improve the symptoms of the condition.²⁶

As IBS is a disorder of the gastrointestinal system, it is unsurprising that one’s diet can affect the symptoms experienced, by those with the condition. One piece of general advice for all those with IBS is to eat meals at regular intervals and drink lots of fluids.²⁴ As for which foods to avoid, research has indicated that high-fat diets exacerbate IBS symptoms.²⁷

Caffeine has similarly been shown to worsen symptoms, as it stimulates rectosigmoid motility of the large intestine, promoting defecation.²⁸ Capsaicin, which is the main ingredient in red chilli, is found in a lot of spicy food, and it stimulates gastrointestinal motility, which may lead to abdominal pain and burning. Therefore, it may be best avoided by those with IBS symptoms.²⁹

Summary 

IBS is the most common of the FGIDs and affects millions of people globally. It is a chronic, biopsychosocial disorder, which has no known cause owing to structural abnormalities. Symptoms of the condition include abdominal pain, bloating, constipation, diarrhoea, lumpy/hard stools, frequent stools and mucus in stools. IBS can be categorised into 3 different subtypes using the Rome IV criteria and the BSFS: IBS-C (predominant constipation), IBS-D (predominant diarrhoea) and IBS-M (mixed bowel habits). There also exists IBS-U for those with symptoms that fit any of the prior 3 subtype diagnosis criteria. 

As IBS symptoms are common to many other diseases, a full medical history and physical examination should be performed on patients with these symptoms to rule out the possibility that the root cause is a different disease.

The different subtypes of the condition have corresponding medications that work better in relieving symptoms. Medications such as lubiprostone and fluoxetine are effective in those with IBS-C, whereas, amitriptyline, rifaximin and octreotide are beneficial in those with IBS-D. Octreotide has a limited benefit in IBS-M too,

Lifestyle and diet are also important factors in IBS, with regular exercise and sleep thought to improve symptoms. Whereas, certain food triggers such as caffeine, spicy, and high-fat foods are best avoided.

Conclusively, these are the main aspects to highlight in terms of IBS. If you are experiencing any discomfort, it is essential to contact a healthcare professional who can describe your gut profile and provide suitable lifestyle advice and medication.