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JariPunkkinen

Functional Bowel Disorders and the Irritable Bowel Syndrome (IBS)

Essentials

  • The diagnosis of irritable bowel syndrome (IBS) is based on the typical symptom picture, i.e. on a carefully taken patient history.
  • By definition, the symptoms always include abdominal pain, which may be associated with defecation or with a change in stool frequency or consistency.
  • IBS is divided into diarrhoea-predominant, constipation-predominant and mixed types.
  • If a patient below 50 has typical IBS symptoms with no warning signs or findings, diagnosis and treatment can be carried out in primary health care.
  • Colonoscopy should always be done for patients with alarming symptoms or findings or near relatives with inflammatory bowel disease or bowel cancer. Colonoscopy is usually also warranted in people over 50 with new symptoms.
  • A good patient-physician relationship is the basis of successful treatment of IBS.
  • Lifestyle changes are often sufficient to treat mild, intermittent symptoms.
  • Medication may be needed for the treatment of severe IBS affecting the quality of life.

Epidemiology and aetiology

  • The prevalence of IBS is 10-15%. IBS is twice as common in women as in men.
  • IBS is believed to be due to disturbed interaction between the bowel and the central nervous system (gut-brain axis).
  • In patients with IBS, the colonic microbiome is less diverse than in healthy people. Bacteroides and Firmicutes species are overrepresented, Clostridiales and Pervotella underrepresented. Butyrate, methane and hydrogen metabolism is disturbed and, in addition, some patients have been reported to have bacterial overgrowth in the small intestine.
    • Yet it is not known how the microbiome is associated with disease mechanisms, which may include visceral hypersensitivity (lowered pain and sensation thresholds), abnormal alimentary tract motility, dysfunction of the autonomic nervous system, increased permeability and low-grade inflammation.
  • Symptoms may be caused by fermentable dietary carbohydrates or amylase trypsin inhibitors. Eating aggravates the abdominal symptoms in more than half of patients with IBS.
  • IBS-type symptoms may sometimes occur after gastroenteritis (post-infectious IBS).
  • Patients with IBS may simultaneously have other functional gastrointestinal symptoms (such as functional dyspepsia) or functional symptoms of other organs (such as overactive bladder or chronic prostatitis).
  • In some patients, IBS is associated with depression, anxiety or somatization.
  • IBS is a chronic disorder with the severity of symptoms varying with time. In less than one patient in five, the symptoms will become more severe over time; in the rest they will remain stable or decrease.

Diagnosis

The diagnostic Rome IV criteria for IBS

  • Recurrent abdominal pain at least 1 day/week in the last 3 months. Symptom onset must, however, have occurred at least 6 months earlier. In addition, two of the following criteria:
    • Abdominal pain is related to defecation.
    • Abdominal pain is associated with a change in the frequency of stool (more or less frequent).
    • Onset of abdominal pain is associated with a change in the form of stool (loose diarrhoeic stools or exceptionally hard stools).
  • Stool frequency is abnormal if there are more than 3 bowel movements per day or less than 3 bowel movements per week.
  • Additional symptoms and findings that support the diagnosis of irritable bowel syndrome include
    • abnormal stool passage (abnormal straining, repeated urgency, feeling of incomplete evacuation)
    • abdominal bloating and meteorism (bloating typically getting worse during the day after meals and disappearing during the night).

IBS subtypes

  • Diarrhoea-predominant IBS (IBS-D): loose or watery stools in at least 25% of bowel movements
  • Constipation-predominant IBS (IBS-C): hard stools in at least 25% of bowel movements
  • Mixed IBS (IBS-M): loose stools in at least 25% and hard stools in at least 25% of bowel movements
  • Undefined IBS (IBS-U): constipation and diarrhoea in less than 25% of bowel movements.

Workup

Patient history

  • The diagnosis is based on typical symptoms.
  • It is important to exclude alarming symptoms and findings (weight loss, prolonged diarrhoea or constipation that is resistant to treatment, blood in stools, fever, nocturnal symptoms, anaemia).
  • It should be established whether there is bowel cancer Colorectal Cancer, coeliac disease Coeliac Disease or inflammatory bowel disease (IBD) Ulcerative Colitis Crohn's Disease in near relatives.
  • Faecal consistency can be assessed using the Bristol stool scale.
  • A defecation diary is useful in determining the severity of constipation.

Clinical examination

  • Abdominal palpation should be done for all patients. Abnormal findings such as a palpable abdominal mass are indications for further investigations. A gynaecological examination should be performed in women with lower abdominal complaints or menstrual disorders.
  • The basic examinations include inspection of the anus and digital rectal examination. Anal fissure Anal Fissure, haemorrhoids Haemorrhoids, rectal tumour Colorectal Cancer and hard faecal mass, rectal prolapse (when straining while squatting), and in women rectocele (abnormal movement of the anterior rectal wall when straining) are findings that should be considered. A wide open or asymmetrically opening anus suggests neurological damage.

Assessment of defecation

  • Investigation of defecation problems may be necessary in patients with constipation.
  • During the digital rectal examination, the examiner places one hand on the patient's lower abdomen and asks the patient to strain as if they were defecating.
    • Normally, abdominal muscles will become tense, the external anal sphincter will be relaxed and the perineum will descend.
    • In patients with dyssynergy, contraction of abdominal muscles is missing, the anal sphincter is not relaxed but paradoxically contracted, and the perineum does not descend.
  • Defecography and manometric examinations can be used to assess defecation in specialized care.

Laboratory tests and imaging

  • The following tests should be done for all patients with abdominal pain: basic blood count with platelet count, CRP, plasma creatinine, ALT and ALP, and, as necessary, chemical screening of urine.

Diarrhoea-predominant and mixed IBS

  • Microbial samples are needed if the symptoms are of sudden onset or were preceded by a trip abroad or a course of antimicrobial medication ( faecal bacterial culture and nucleic acid testing, parasites nucleic acid testing, and C. difficile toxin gene and nucleic acid testing).
  • Laboratory tests should be used to exclude inflammatory bowel disease Ulcerative Colitis Crohn's Disease (faecal calprotectin) and coeliac disease Coeliac Disease (primarily transglutaminase antibodies).
    • F-Calpro levels are also elevated in acute gastroenteritis but they are usually not elevated in Crohn's disease of the small intestine.
  • If lactose malabsorption Lactose Intolerance is suspected, gene testing for lactose intolerance or a dietary trial should be performed.
  • If bile acid diarrhoea is suspected, a treatment test with cholestyramine or, alternatively, a bile acid absorption test should be performed.
  • If the IBS symptom is new in a patient over 50, colonoscopy should be performed.
  • If diarrhoea has continued for more than a month, colonoscopy should be performed even if the patient is below 50 to exclude inflammatory bowel disease Ulcerative Colitis Crohn's Disease and microscopic colitis Microscopic Colitis.

Constipation-predominant IBS

  • Perform TSH and free T4, fasting blood glucose, plasma creatinine, potassium and plasma albumin-corrected calcium tests, as considered necessary.
  • If the IBS symptom is new in a patient over 50, colonoscopy should be performed.
  • In elderly patients with abdominal pain and constipation, computer tomography of the colon may be sufficient to exclude malignancies and also allows imaging of other abdominal organs.
  • Plain abdominal X-ray is more rarely done but can be used to show severe faecal retention and megacolon.

Indications for colonoscopy

  • Colonoscopy in order to detect malignant tumours, polyps, inflammatory bowel disease and diverticulosis is warranted especially if
    • the patient is aged over 50 years
    • there are alarming symptoms or findings
    • symptoms have continued for less than 6 months (not fulfilling the criteria for IBS)
    • there has been bowel cancer or inflammatory bowel disease in the near family
    • diarrhoea has continued for more than 1 month.
  • Symptoms of IBS may also be present concurrently with an organic disease, and diagnosing IBS will not eliminate the need for screening for bowel cancer if the patient belongs to an age group being screened.

Differential diagnosis

Diarrhoea-predominant IBS

Constipation-predominant IBS

  • Disorders to be considered include hypothyroidism Hypothyroidism, bowel cancer Colorectal Cancer, drug-induced constipation, slow transit constipation and dyssynergic defecation.
  • Drugs, such as antidepressants and antipsychotics, iron products, opioids and calcium channel blockers, may cause constipation.

Treatment

  • It is important to diagnose IBS and to inform the patient about this, not just to note that the examination results were normal.
  • A positive relationship should be established with the patient; in practice, this means inviting the patient for at least one follow-up visit.
  • The patient should be explained that IBS is a chronic disorder but does not involve a risk of malignancy.
  • The symptoms and exacerbating factors should be discussed with the patient. Explaining the pathophysiology of the symptoms is often beneficial.
  • Patient material with dietary instructions is useful for providing information.
  • The diagnosis of functional abdominal problems is usually reliable and investigations, such as endoscopy, should not be repeated if there is no change in symptoms.

Diet

  • Consulting a therapeutic dietitian is useful for the treatment of severe IBS.
  • The effect of dietary changes will only become apparent with delay.

Traditional IBS diet

  • Regular eating, small portions, sufficient intake of fibre and liquids, and avoiding alcohol, caffeine, fat, and spicy food are generally recommended.
  • The Nordic dietary recommendations for IBS additionally suggest avoiding cruciferous vegetables, leguminous and bulbous plants, lactose and artificial sweeteners, as well as insoluble fibre.
  • The recommended fibre intake is 20-35 g daily. The fibre should be long-chain semi-viscous moderately fermentable fibre. The fibre product should be started at a low dose to avoid bloating.
  • The best research evidence is on psyllium (ispaghula), and the product should be used for the treatment of every IBS subtype.
  • Other fibre products include linseed (flaxseed), sterculia and methyl cellulose, which have been recommended for the treatment of constipation-predominant IBS.

FODMAP diet

  • FODMAP = fermentable oligosaccharides (from leguminous plants, for instance), disaccharides (such as lactose), monosaccharides (such as fructose) and polyols (such as sorbitol and xylitol)
  • A 4-8-week elimination diet avoiding FODMAP carbohydrates under the supervision of a therapeutic dietitian is recommended for patients who suffer from abdominal bloating and pain. Foods can then gradually be included in the diet according to individual consideration.
  • Foods to be avoided:
    • Cereals: rye, wheat and barley
    • Fruits and vegetables: apples, pears, plums, apricots, cherries, water melon, cabbage, onions, asparagus, artichokes
    • Mushrooms
    • Leguminous plants: peas, beans
    • Sweeteners: xylitol, sorbitol, mannitol, maltitol
    • Prebiotics (inulin, fructo-oligosaccharides [FOS]), e.g. “digestion-improving” yoghurts and “health drinks” that contain added fibre (FOS or inulin)
    • Honey
  • In two comparative studies, the FODMAP diet was no better than the traditional Nordic IBS diet, from which FODMAP carbohydrates have been largely eliminated in practice.
  • However, in four long-term studies (6-16 months), FODMAP decreased abdominal pain, bloating, flatulence and diarrhoea in patients with IBS.
  • A strict FODMAP diet may be nutritionally insufficient, and it will reduce the amount of bacteria favourable for the intestine (bifidobacteria).

Gluten-free diet

  • Gluten causes symptoms in as many as 10% of the population and in 30% of patients with IBS even if they have not been diagnosed with coeliac disease.
    • However, it is not necessarily gluten as such that causes the symptoms but avoidance of cereals also helps to reduce the amount of fructane (a FODMAP carbohydrate) and, in addition, cereals contain amylase trypsin inhibitors, which may impair the function of digestive enzymes and cause abdominal discomfort.
  • On the other hand, gluten has been found to affect the mucosal barrier function in HLA-DQ2/8-positive patients with diarrhoea-predominant IBS.

Exercise

  • Physical exercise accelerates the bowel passage of gaseous contents in healthy individuals and of faeces in individuals suffering from constipation. Physical activity reduces IBS symptoms. Excessively hard physical exercise may cause bowel urgency, diarrhoea and abdominal cramps, but moderate physical activity may be beneficial in the treatment of IBS.
  • Physical exercise is recommended as, for instance, 20-60 minutes of moderate or strenuous exercise 3-5 times a week. In physically inactive people, less exercise, such as walking 20 minutes daily, is initially sufficient.

Pharmacotherapy Bulking Agents, Antispasmodic and Antidepressant Medication for the Treatment of Irritable Bowel Syndrome

  • Drug therapy should be used if the symptoms disturb the patient's daily life.
  • The choice of drug depends on the IBS subtype and the predominant symptom.
  • The best research evidence is on psyllium fibre, loperamide, linaclotide and tricyclic antidepressants.

Abdominal pain

  • Antispasmodic, or anticholinergic, drugs can be used for the treatment of alimentary tract spasms and postprandial abdominal complaints.
  • 1-2 peppermint oil capsules can be taken three times daily as necessary or for 2-3 months.
  • Severe abdominal pain impairing the quality of life is also treated with tricyclic antidepressants (amitriptyline, trimipramine, clomipramine, doxepin).
    • Adverse effects restrict the use of tricyclic antidepressants (constipation, dry mouth, fatigue or confusion in 30% of users).
    • Treatment should be started with a low dose (10 mg in the evening) increased gradually every 4 weeks to a target level of 25-100 mg (usually the daily dose cannot exceed 30 mg). The treatment should be continued for 6-12 months and then be gradually tapered off.
  • Alternatively, the tetracyclic antidepressants mirtazapine or mianserin can be used, particularly if there is insomnia, or the SNRI drugs duloxetine (30-90 mg) or venlafaxine (225 mg).
  • Selective serotonin reuptake inhibitors (SSRIs) improve the quality of life in patients with chronic refractory IBS. The positive effect is associated with the alleviation of anxiety, depression or somatization disorders because these drugs have no effect on the symptoms of IBS or on abdominal pain.
  • Linaclotide, a non-absorbable agonist of guanylate cyclase-C receptors, can be used for the treatment of both abdominal pain and constipation in patients with IBS-C. It treats constipation by increasing intestinal fluid secretion and abdominal pain by stimulating the nerve endings in the intestinal wall.

Diarrhoea

  • Loperamide can be used regularly or as needed for diarrhoea-predominant IBS. Research data on racecadotril showing decreased water and electrolyte excretion is only available for the treatment of acute diarrhoea.
  • A combination product with xyloglucan, pea protein and xylooligosaccharides has also been shown to decrease diarrhoea in patients with IBS.
  • Diarrhoea-predominant IBS is sometimes caused by bile acid malabsorption, which is treated with 4 g cholestyramine 2-4 times daily.
  • Of soluble fibres, psyllium is also recommended for the treatment of diarrhoea-predominant IBS.
  • Rifaximin has been used in courses of 2 weeks for patients with other than constipation-predominant IBS, in whom limiting FODMAPs did not alleviate bloating. Rifaximin is about 10% more effective than placebo but its effect is transient. Its effect is based on controlling excess bacterial growth in the small intestine. Empiric use of rifaximin may be considered in patients of advanced age with IBS causing diarrhoea and bloating who use acid blockers regularly. The drug is rather expensive.

Constipation

  • The primary treatment is psyllium fibre.
  • Polyethylene glycol products (PEG, macrogol) are used if psyllium is ineffective.
  • Adverse effects may restrict the use of lactulose in the treatment of constipation in patients with IBS.
  • Linaclotide treats constipation by increasing intestinal fluid secretion and decreases abdominal pain by affecting peripheral nerve endings in the intestine.
  • The 5HT4-receptor agonist prucalopride binding to enteric neurons reduces the large intestinal transit time in approx. 30-40% of patients but its official indication is constipation.

Probiotics and faecal transfusion

  • In patients with IBS, probiotics lower the total symptom score, and of individual symptoms they reduce abdominal pain and bloating but their effect on diarrhoea, constipation and flatulence is poor.
  • There is research evidence for several probiotics, such as several Bifidobacterium (e.g. B. infantis 35624), Lactobacillus and Saccharomyces strains and mixtures of probiotics. There should be 109 CFS units of microbes per dose. There is often less clinical experience than research evidence of the usefulness of probiotics in the treatment of IBS.
  • In some studies, faecal transplantation has reduced the total IBS symptom score at 3 months compared to placebo but no long-term follow-up data are available. The success of faecal transplantation depends on the route of administration and the quality of the donated faeces.
    • For the time being, faecal transplantation is an experimental treatment for IBS and should only be used in association with studies.

Other forms of treatment Biofeedback for Treatment of Irritable Bowel Syndrome, Homeopathy for Treatment of Irritable Bowel Syndrome

  • Yoga, relaxation exercises and hypnotherapy Hypnotherapy for Treatment of Irritable Bowel Syndrome have been reported to be helpful in the treatment of IBS symptoms.
  • Patients with moderate or severe anxiety or depression and IBS may benefit from psychotherapy if standard IBS treatment is ineffective Psychological Treatments for Irritable Bowel Syndrome.
  • Aspirin and other NSAIDs and paracetamol are ineffective in the treatment of IBS-associated pain. NSAIDs additionally cause mucosal damage.
  • Opioids are contraindicated because of their adverse effects (narcotic bowel syndrome) and the risk of dependence.

Summary of IBS treatments

Type of IBSSymptoms
IBS-D (diarrhoea-predominant IBS)DiarrhoeaBloatingPain
Primary
Loperamide, psyllium, cholestyramineFODMAP avoidance, probioticsAntispasmodics, peppermint oil capsules, probiotics
Secondary
XG+PPT+XOS* , rifaximinRifaximinTricyclic antidepressants (TCA) and tetracyclic antidepressants, SNRI, psychotherapy
IBS-C (constipation-predominant IBS)ConstipationBloatingPain
Primary
Psyllium, macrogolFODMAP avoidance, probioticsAntispasmodics, peppermint oil capsules, probiotics, linaclotide
Secondary
Linaclotide, prucalopride Tetracyclic antidepressants, SNRI, psychotherapy
IBS-M
(mixed type IBS)		Diarrhoea/constipationConstipation/bloatingPain
Primary
PsylliumFODMAP avoidance, probioticsAntispasmodics, peppermint oil capsules, probiotics
Secondary
Diarrhoea: withdrawal of laxative
Constipation: withdrawal of loperamide
 TCA, tetracyclic antidepressants, SNRI or psychotherapy
* XG+PPT+XOS = combination product with xyloglucan, pea protein and xylooligosaccharides
Follow-up
  • A long-term, supporting doctor-patient relationship is essential for successful treatment.
  • For a long-term doctor-patient relationship to succeed and to facilitate assessing the efficacy of treatment, follow-up visits are usually needed in the beginning, at least.

    References

    • Tap J, Derrien M, Törnblom H ym. Identification of an Intestinal Microbiota Signature Associated With Severity of Irritable Bowel Syndrome. Gastroenterology 2017;152(1):111-123.e8.[PubMed]
    • Drossman DA. Functional Gastrointestinal Disorders: History, Pathophysiology, Clinical Features and Rome IV. Gastroenterology 2016;():. [PubMed]
    • Ford AC, Moayyedi P, Chey WD et al. American College of Gastroenterology Monograph on Management of Irritable Bowel Syndrome. Am J Gastroenterol 2018;113(Suppl 2):1-18. [PubMed]
    • Rej A, Aziz I, Tornblom H et al. The role of diet in irritable bowel syndrome: implications for dietary advice. J Intern Med 2019;286(5):490-502. [PubMed]
    • Drossman DA, Tack J, Ford AC et al. Neuromodulators for Functional Gastrointestinal Disorders (Disorders of Gut-Brain Interaction): A Rome Foundation Working Team Report. Gastroenterology 2018;154(4):1140-1171.e1. [PubMed]
    • Hungin APS, Mitchell CR, Whorwell P et al. Systematic review: probiotics in the management of lower gastrointestinal symptoms - an updated evidence-based international consensus. Aliment Pharmacol Ther 2018;47(8):1054-1070. [PubMed]
    • Wang Y, Zheng F, Liu S et al. Research Progress in Fecal Microbiota Transplantation as Treatment for Irritable Bowel Syndrome. Gastroenterol Res Pract 2019;2019():9759138. [PubMed]

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