Irritable bowel syndrome (suspected)

According to the most recent iteration of the ROME criteria (ROME IV) from the Rome Foundation, IBS has a worldwide prevalence of about 4% 1, 2 . (This figure is lower than that obtained using ROME III criteria, due to the more restrictive criteria under ROME IV 3 ).

IBS is commonest in women below the age of 50 year and may account for about a third of patients presenting in primary care practice with gastrointestinal symptoms 4 .

IBS is regarded as one of the Gut-Brain interaction disorders and is frequently associated with psychosocial disturbances.

The diagnosis of IBS is based on the Rome IV criteria 5-8 . Essential criteria for diagnosis include:

• recurrent abdominal pain, occurring at least once per week for the past 3 months, with symptom onset at least 6 months before diagnosis. 

• The pain should be associated with two or more of the following:

•  pain related to defecation. 

• changes in defecation stool frequency,

• change in stool form/appearance.

The absence of abdominal pain precludes the diagnosis of IBS 8 . A disordered bowel habit is needed for diagnosis, but bloating is not necessary. It is also important to employ a multiple dimensional clinical profile (MDCP) approach when treating IBS patients which includes consideration of categorical diagnosis, clinical modifiers, impact on daily activities, psychosocial modifiers, and physiological modifiers of function and biomarkers 9 .

There is some controversy as to whether ROME IV is adequate for diagnosis of IBS (being more suitable for severe than mild cases) 10 .

It is important to note that some patients with organic disease also meet the ROME IV diagnostic criteria and, as such, the sensitivity and specificity of these criteria is suboptimal to distinguish the different disease entities 11 . The presence of alarm features Atypical features which may point to organic disease must be elicited.

There is also increasing recognition that dietary factors, changes in small bowel microbes (small bowel overgrowth) or bile acid diarrhoea may play part in individual cases. Relationship of symptoms to eating is not a part of the ROME IV criteria. However, self-reported food intolerances and triggering of symptoms by various foods are very common 12, 13 .

There is an overlap of IBS with other Functional Gastrointestinal Disorders(FGIDs) Abdominal Pain (Adult, Chronic), and thus IBS is best recognised as a Disorder of Gut-Brain Interaction (DGBI) 14, 15 . Of note is that a recent study reported that of 54,127 adults from 26 countries who participated in an internet survey, 22% had symptoms related to more than one gastrointestinal anatomical region 16 and that such patients tended to have more severe IBS and greater psychological morbidity.

There is overlap between IBS of diarrhoea type with “Functional Diarrhoea” 17 . The latter, as defined by the Rome IV criteria, is similar to the former, but without dominant abdominal pain 8 . It is therefore useful to regard these functional disorders as a spectrum of disease. 

Of note, there is evidence of substantial movement of patients between subtypes of IBS 18 .

IBS is classified into four subtypes 6 .

• IBS with predominant constipation (IBS-C). This requires the patient to have at least 25% hard stools. It is frequently associated with abdominal pain related to bowel movements and bloating. 

• IBS with predominant diarrhoea (IBS-D). This requires the patient to have at least 25% loose stools. As for IBS-C, this is associated with abdominal pain related to bowel movements and bloating.

• IBS with mixed bowel habits (IBS-M). At least 25% hard stools and at least 25% loose stools are required, with alternation. 

• IBS patients who fulfil the criteria for IBS but whose bowel habit cannot be adequately categorised into any of the above types (IBS-U).

Reference to the Bristol Stool Chart (8, 19, 20) can best place the patient into one of the IBS subtypes 6 .

• • Stool consistency is best documented according to the Bristol Stool Chart 8, 19, 20 and can best place the patient into one of the IBS subtypes 6.

  • A full history should be taken to aid exclusion of other causes of bowel symptoms such as iatrogenic (medication) or infective/infestation causes of diarrhoea.

  • A history should be sought of travel to regions where intestinal parasites and infective diarrhoea are endemic. There is evidence that some IBS patients may have a history of infectious diarrhoea 21.

  • A dietary history should be taken to elicit symptom-triggering foods. The majority of IBS patients self-report food triggers for their symptoms 12, 13.

  • A history of previous cholecystectomy or ileal resection increases the likelihood of bile acid diarrhoea.

  • Abdominal physical examination.

  • A digital rectal examination (for pelvic dyssynergia in IBS-C and for pelvic/rectal masses – diagnostic tests.

  • A Carnett sign should be sought for evidence of Chronic Abdominal Wall Pain Abdominal Pain (Adult, Chronic).

  Before diagnosing IBS, it is crucial to thoroughly investigate if warning/alarm/”red flag” signs are present 22, 23 as follows:

  • onset of symptoms after the age of 50

  • recent change in bowel habit

  • unintentional weight loss 

  • anorexia/early satiety

  • overt gastrointestinal bleeding/blood in stool

  • recent changes in bowel habits

  • nocturnal pain or passage of stools 

  • palpable abdominal mass or lymphadenopathy

  • family history of colon cancer or inflammatory bowel disease

  • Iron deficiency anaemia

  • Positive testing for faecal occult blood

  • Fever

  In addition the American College of Gastroenterology Task force adds antibiotic use to its list of alarm features 24.

  Note that a study of the predictive value of alarm features in patients initially diagnosed with IBS under the ROME IV criteria found that anaemia, faecal occult blood and unintended weight loss each had a positive predictive value of about 15-23% for organic disease, and 100% predictive value when combined. However, the presence of these features when combined with ROME IV criteria do not exclude IBS 11.

The diagnosis of IBS is based on the Rome IV criteria 5-8. Essential criteria for diagnosis include:

• Recurrent abdominal pain, occurring at least once per week for the past 3 months, with symptom onset at least 6 months before diagnosis.

• The pain should be associated with two or more of the following:

•  pain related to defecation

• changes in defecation stool frequency

• change in stool form/appearance

• IBS is classified into four subtypes 6.

  • IBS with predominant constipation (IBS-C). This requires the patient to have at least 25% hard stools. It is frequently associated with abdominal pain related to bowel movements and bloating. 

  • IBS with predominant diarrhoea (IBS-D). This requires the patient to have at least 25% loose stools. As for IBS-C, this is associated with abdominal pain related to bowel movements and bloating.

  • IBS with mixed bowel habits (IBS-M). At least 25% hard stools and at least 25% loose stools are required, with alternation. 

  • IBS patients who fulfil the criteria for IBS but whose bowel habit cannot be adequately categorised into any of the above types (IBS-U).

  Of note, there is evidence of substantial movement of patients between subtypes of IBS 18.

  The use of the Bristol Stool Chart (8, 19, 20) can best place the patient into one of the IBS subtypes 6.

  Assessment of stool 6:

  Bristol Stool type	Consistency
  Type 1:	Separate hard lumps, like nuts (hard to pass)
  Type 2:	Sausage-shaped, but lumpy
  Type 3:	Like a sausage, but with cracks on the surface
  Type 4:	Like a sausage or snake, smooth and soft
  Type 5:	Soft blobs with clear-cut edges
  Type 6:	Fluffy pieces with ragged edges, a mushy stool
  Type 7:	Watery, no solid pieces, entirely liquid

  Assessment should be based on days of abnormal bowel

  • In IBS-C, Bristol types 1 or 2 are present in at least 25% of bowel movements.

  • In IBS-D, Bristol types 6 or 7 are present in at least 25% of bowel movements.

  • In IBS-M, at least 25% of bowel movements are types 6 or 7 plus at least 25% are types 1 or 2.

The Rome IV criteria should be applied to make a positive diagnosis 25. The Rome IV criteria for the diagnosis of IBS perform significantly better than the previous iteration (Rome III) 26.

• If the Rome criteria are fulfilled, that is if a patient presents with symptoms consistent with IBS, (see below) the yield of diagnostic tests to rule out organic disease is low 23, 27, 28.

• The use of a positive diagnostic strategy is non-inferior to using a strategy of exclusion by performing a barrage of tests 29, 30 .This is supported by a longitudinal study that showed the stability of a IBS diagnosis; the development of subsequent Inflammatory Bowel Disease (IBD) or colorectal cancer (CRC) is rare 31.

• A study involving 466 patients with the diarrheal or mixed subtype of IBS who underwent colonoscopy, reported no cases of colorectal cancer detected, and inflammatory bowel disease (IBD) was observed in less than 2% of the patients 32.

• A 2023 meta-analysis 33 found no increase in  colorectal cancer among IBS patients undergoing colonoscopy, compared to non-IBS patients . CRC was rare in IBS patients without alarm symptoms or younger than 40 years (<0.1%). The pooled prevalence of CRC and IBD was significantly higher in IBS patients with alarm symptoms than in those without. CRC and IBD were more likely to be detected at colonoscopy in IBS-D compared with IBS-C patients.

• Another study found the diagnostic yield of upper endoscopy and colonoscopy for organic disease to be low in patients with a first-time diagnosis of IBS, though it increases with age 34

• Laboratory diagnostic tests:

However, the American College of Gastroenterology guidelines  35, 36 and the Guidelines of the United European Gastroenterology and European Society for Neurogastroenterology and Motility 17 state that it is reasonable to perform limited diagnostic tests to rule out less common causes of similar symptoms, such as:

• complete blood count and C-reactive protein measurement to help rule out inflammatory bowel disease (IBD). If a patient’s CRP level is quite low (<0.5 mg/L), IBD is highly unlikely 35.

• Faecal lactoferrin measurement.  This has a very high sensitivity and specificity for excluding IBD 35.

• Results for faecal lactoferrin and faecal calprotectin show concordance (90%) 37.

• In patients with diarrhoea a measurement of the faecal calprotectin level is useful because it can discriminate between IBS and inflammatory bowel disease with good accuracy (i.e., high sensitivity and specificity) 25, 38, 39 and is particularly important in patients presenting with diarrhoea at age <45 years 28.

• A combination of the Rome diagnostic criteria and a negative faecal calprotectin has a predictive value for IBS of nearly 100% 40. A normal faecal Calprotectin level may thus replace the need for colonoscopy . 

• Thyroid Stimulating Hormone (TSH) to exclude thyroid overactivity (IBS-D) or underactivity (IBS-C). 

• Guidelines for the management of celiac disease (CD) 41, supported by a meta-analysis, recommend screening persons with IBS-type symptoms by means of serologic testing as the prevalence of CD among patients with IBS symptoms (of any type) is significantly increased 42.The American College of Gastroenterology guidelines support the use of celiac serology in patients with IBDS-D 25.

• Colonoscopy: See above. In addition, the British Society of Gastroenterology (BSG) guidelines 43 state that “there is no role for colonoscopy in IBS, other than in those with alarm symptoms or signs, or those with symptoms suggestive of IBS with diarrhoea who have atypical features and/or relevant risk factors that increase the likelihood of them having microscopic colitis (female sex, age ≥50 years, coexistent autoimmune disease, nocturnal or severe, watery, diarrhoea, duration of diarrhoea <12 months, weight loss or use of potential precipitating drugs including non-steroidal anti-inflammatory drugs, proton pump inhibitors, etc.”

The European guidelines 17 suggest that in patients over the age of 50 years Appropriate investigations, colonoscopy with multiple biopsies should be performed to exclude colorectal cancer and microscopic colitis.

• A digital rectal examination, especially in patients with constipation to elicit  paradoxical contraction on straining indicating  obstructive defaecation/pelvic-floor dyssynergia

23. If positive, these patients may require anal manometry and/or evacuation proctography (fluoroscopic, CT or MRI methods). The British Society of Gastroenterology guidelines 43 indicate that for patients with IBS and coexisting symptoms suggestive of a defaecatory disorder or faecal incontinence, “anorectal physiology tests can be considered, where available, to select those who might benefit from biofeedback .”

• Digital pelvic and rectal examinations are also required in post-menopausal women to detect a pelvic mass, which may lead to transabdominal and transvaginal ultrasonography23 .

• Ultrasound has also been suggested in women with predominantly lower abdominal pain, bloating and distension to exclude gynaecological malignancy 23, 44

•  A 2012 review 27found a dearth of evidence guiding radiologic imaging in patients with symptoms of IBS. Radiological investigation may not be required in patients with IBS without concerning/alarm features but should be considered where such symptoms exist. The choice of imaging study should be influenced by predominant symptoms. A list of alarm symptoms and suggested investigation approach is shown IN Alarm/Warning symptoms/signs?:

   

A significant proportion of patients diagnosed with IBS have the following:

• Bile acid diarrhoea (BAD). A meta-analysis 45, of studies employing the administration of a radio-labelled bile acid, has shown that approximately 25% of patients with diarrhoea-type IBS have evidence of bile acid diarrhoea. This may lead to a possible therapeutic approach using bile acid sequestering agents. In a further systematic review estimated the prevalence of BAD at 41% 46. It is important to note that the studies included in this systematic review do not appear to be confined to patients with IBS-D or IBS-M.

The BSG guidelines 43 recommend that in patients with symptoms suggestive of IBS with diarrhoea, but with atypical features such as nocturnal diarrhoea, or a history of prior cholecystectomy, 23-seleno-25-homotaurocholic acid scanning or serum 7α-hydroxy-4-cholesten- 3-one should be considered to exclude bile acid diarrhoea.

• Microscopic colitis (MC).The same meta-analysis referred to above 46 estimated a prevalence of MC as 3%. The BSG guidelines 43 recommend colonoscopy to exclude MC in patients with “atypical features and/or relevant risk factors that increase the likelihood of them having microscopic colitis (female sex, age ≥50 years, coexistent autoimmune disease, nocturnal or severe, watery, diarrhoea, duration of diarrhoea <12 months, weight loss or use of potential precipitating drugs including non-steroidal anti-inflammatory drugs, proton pump inhibitors, etc.”. The European guidelines 17 suggest colonoscopy in patients over the age of 50 years.  All guidelines recommend colonoscopy when relevant alarm features are present.

• Carbohydrate Malabsorption in the same systematic review referred to above was estimated to have a prevalence of 43-54% 46.

• Small Bowel Bacterial Overgrowth (SBBO) prevalence was estimated at 49% 46 However, the relationship of SBBO to IBS remains controversial 47, 48.

• Pancreatic Exocrine Insufficiency prevalence was estimated at 4.6% 46

The above figures for these underlying conditions were higher than in normal healthy controls, although a recent meta-analysis of colonoscopy in patients with IBS found no difference for the yield of MC between IBS and non-IBS patients 33.

The BSG guidelines 43 conclude that there is no role for laboratory testing to exclude Carbohydrate Malabsorption, Small Bowel Bacterial Overgrowth or Pancreatic Exocrine Insufficiency in patients with typical features of IBS.

Currently, prediction of responses to empirical treatment of underlying disorders such as SBBO, food intolerance and bile acid malabsorption and motility disorder is limited by the availability of sufficiently sensitive and specific tests for the underlying mechanisms that may lead to symptoms 49.

Before diagnosing IBS, it is crucial to thoroughly investigate if warning/alarm/”red flag” signs are present 22, 23 as follows:

• onset of symptoms after the age of 50

• recent change in bowel habit

• unintentional weight loss 

• anorexia/early satiety

• overt gastrointestinal bleeding/blood in stool

• recent changes in bowel habits

• nocturnal pain or passage of stools 

• palpable abdominal mass or lymphadenopathy

• family history of colon cancer or inflammatory bowel disease

• Iron deficiency anaemia

• Positive testing for faecal occult blood

• Fever

In addition the American College of Gastroenterology Task force adds antibiotic use to its list of alarm features 24

Atypical diarrhoea

The BSG guidelines 43 recommend colonoscopy to exclude MC in patients with “atypical features and/or relevant risk factors that increase the likelihood of them having microscopic colitis (female sex, age ≥50 years, coexistent autoimmune disease, nocturnal or severe, watery, diarrhoea, duration of diarrhoea <12 months, weight loss or use of potential precipitating drugs including non-steroidal anti-inflammatory drugs, proton pump inhibitors, etc.”.

Patients with constipation and suspected obstructed defaecation or patients with faecal incontinence

Some patients have symptoms of a functional defaecation disorder characterised by either obstructed (dyssynergic) defaecation, or faecal incontinence - and defined by the Rome IV criteria 6. Patients with dyssynergic defaecation may or may not have co-existing features of IBS-C.

The British Society of Gastroenterology guidelines 43 indicate that for patients with IBS and co-existing symptoms suggestive of a defaecatory disorder or faecal incontinence, “anorectal physiology tests can be considered, where available, to select those who might benefit from biofeedback .”

The American College of Radiology Appropriateness Criteria recommend either fluoroscopic (barium) or MR evacuation proctography for the investigation of obstructed defaecation/pelvic dyssynergia 50.

Atypical diarrhoea

The BSG guidelines 43 recommend colonoscopy to exclude MC in patients with “atypical features and/or relevant risk factors that increase the likelihood of them having microscopic colitis (female sex, age ≥50 years, coexistent autoimmune disease, nocturnal or severe, watery, diarrhoea, duration of diarrhoea <12 months, weight loss or use of potential precipitating drugs including non-steroidal anti-inflammatory drugs, proton pump inhibitors, etc.”.

Patients with constipation and suspected obstructed defaecation or patients with faecal incontinence

Some patients have symptoms of a functional defaecation disorder characterised by either obstructed (dyssynergic) defaecation, or faecal incontinence - and defined by the Rome IV criteria 6. Patients with dyssynergic defaecation may or may not have co-existing features of IBS-C.

The British Society of Gastroenterology guidelines 43 indicate that for patients with IBS and coexisting symptoms suggestive of a defaecatory disorder or faecal incontinence, “anorectal physiology tests can be considered, where available, to select those who might benefit from biofeedback .”

The American College of Radiology Appropriateness Criteria recommend either fluoroscopic (barium) or MR evacuation proctography for the investigation of obstructed defaecation/pelvic dyssynergia 50.