Irritable bowel syndrome (IBS) - An overview

Contents

Complex, functional gastrointestinal disorder characterized by chronic abdominal pain or discomfort and altered bowel habits.

Epidemiology

♀ > ♂ (3x)

IBS prevalence in population studies around the world | Enck, P., Aziz, Q., Barbara, G., Farmer, A. D., Fukudo, S., Mayer, E. A., … Spiller, R. C. (2016). Irritable bowel syndrome. Nature Reviews Disease Primers, 2(1), 16014. https://doi.org/10.1038/nrdp.2016.14

Classification

Constipation-predominant IBS (IBS-C) or BSFS type 1/2)
Diarrhoea predominant IBS (IBS-D) or BSFS type 6/7
Mixed subtype IBS (IBS-M) (M/C)

Postinfectious IBS (IBS-PI): Characterized by persistent abdominal pain and diarrhoea, typically following an episode of infectious gastroenteritis.

Irritable bowel syndrome subtypes. | IBS: irritable bowel syndrome; IBS-C: IBS with constipation; IBS-D: IBS with diarrhoea; IBS-M: IBS with constipation/diarrhoea; IBS-U: IBS unclassifiable. | Lacy et al., 2016

Etiology

Disease associations:

IBS-associated comorbidities: A model of irritable bowel syndrome (IBS) and its associations with other clinical, intestinal, extra-intestinal and psychiatric conditions. The different components should be viewed as layers of complexity: the IBS subtypes are part of the group of functional bowel disorders, these are part of all kinds of functional disorders and these again are part of a `layer’ of psychiatric disorders. | GERD, gastroesophageal reflux disease; IBS-C, IBS with constipation; IBS-D, IBS with diarrhoea; IBS-M, mixed-type IBS; IBS-U, unsubtyped IBS; PMS, premenstrual syndrome. | Enck, P., Aziz, Q., Barbara, G., Farmer, A. D., Fukudo, S., Mayer, E. A., … Spiller, R. C. (2016). Irritable bowel syndrome. Nature Reviews Disease Primers, 2(1), 16014. https://doi.org/10.1038/nrdp.2016.14

Postinfectious IBS (IBS-PI):

Conceptual model for post-infectious IBS | Thabane, M., & Marshall, J. K. (2009). Post-infectious irritable bowel syndrome. World journal of gastroenterology, 15(29), 3591–3596. https://doi.org/10.3748/wjg.15.3591

Pathophysiology

Gut-brain-axis:
Serotonin (5-HT) may contribute to the postprandial symptoms of these patients and provide a rationale for the use of serotonin antagonist in the treatment of this disorder.

Cortical structures associated with IBS:
- Mid cingulate cortex
- Prefrontal lobe

Graphical summary of pathways involved in IBS | Ng, Q. X., Soh, A., Loke, W., Lim, D. Y., & Yeo, W. S. (2018). The role of inflammation in irritable bowel syndrome (IBS). Journal of inflammation research, 11, 345–349. https://doi.org/10.2147/JIR.S174982

Visceral hypersensitivity:

Increased end-organ sensitivity with recruitment of “silent” nociceptors
Spinal hyperexcitability with activation of nitric oxide and possibly other neurotransmitters
Endogenous (cortical and brainstem) modulation of caudal nociceptive transmission
Development of neuroplasticity

IBS-D:

High-amplitude propagating contractions (HAPCs)
Rapid colonic transit and accompanied by abdominal pain

Presentation

Defining features of IBS are the presence of recurrent abdominal pain in association with altered bowel habits (diarrhoea, constipation or both). The spectrum, duration and severity of symptoms can range from inconvenient to incapacitating and can prevent individuals from participating in everyday activities.

Favour diagnosis:

Abdominal pain or discomfort which improves with defecation
Association of symptoms with stress or emotional upset
Absence of fever and weight loss
Small volume stools
No evidence of blood in stools

Against diagnosis:

First time in old age
Progressive course
Persistent diarrhoea after a 48 hour fast
Presence of nocturnal diarrhoea
Steatorrheal stools

Diagnosis

Rome IV diagnostic criteria:
Recurrent abdominal pain, on average, at least 1 day/week in the last 3 months associated with ≥ 2 of the following for the last 3 months with symptom onset at least 6 months before diagnosis.

Related to defecation
Associated with a change in the stool frequency
Associated with a change in the stool form (appearance)

Irritable bowel syndrome (IBS) diagnosis — Simplified algorithm for irritable bowel syndrome (IBS) diagnosis. | Moayyedi, P., Mearin, F., Azpiroz, F., Andresen, V., Barbara, G., Corsetti, M., … Tack, J. (2017). Irritable bowel syndrome diagnosis and management: A simplified algorithm for clinical practice. United European Gastroenterology Journal, 5(6), 773–788. https://doi.org/10.1177/2050640617731968

Management

Dietary management:

Low FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) diet: Ingestion of FODMAPs such as lactose, fructose, or sorbitol, alone or in combination, produce gut symptoms such as gas and diarrhoea.
Low lipids

5HT3 antagonists:

Alosetron | S/E: Ischaemic colitis
Tegaserod | S/E: Cardiac toxicity.
Lubiprostone| S/E: Nausea, headache, diarrhea, allergic reactions, and dyspnea.

Antidepressants:

SSRI:
- Paroxetine in IBS – C
- Citalopram for pain and IBS – D
TCA:
- Imipramine in IBS – D
- Desipramine in IBS – D and abdominal pain

Summary: