Irritable Bowel Syndrome (IBS)

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Irritable bowel syndrome (IBS) is a “disorder of gut-brain interaction” characterized by a group of symptoms that commonly include abdominal pain and or abdominal bloating and changes in the consistency of bowel movements.

Types of IBS :

1. IBS-C (IBS with constipation)
2. IBS-D (IBS with diarrhea)
3. IBS-M (IBS with mixed bowel movements; constipation and diarrhea both)

Causes for IBS:

1. Muscle contractions in the intestine that are stronger and last longer than usual can cause gas, bloating and diarrhea and weak contractions can slow food passage and lead to hard, dry stools.
2. Poorly coordinated signals between the brain and the intestines can result in abdominal pain, diarrhea or constipation.
3. IBS can develop after a severe bout of diarrhea caused by bacteria or a virus and it can also be associated with a surplus of bacteria in the intestines (bacterial overgrowth).
4. People exposed to stressful events, especially in childhood, tend to have more symptoms of IBS.
5. Food sensitivity to certain foods like wheat, dairy products, beans, cabbage etc. can trigger IBS symptoms.
6. Changes in bacteria, fungi and viruses, which reside in the intestines and play a key role in health cause cause IBS.

• Studies have shown that 3%-36% of enteric infections lead to persistent IBS symptoms. Bacterial enteritis and protozoan and helminth infections lead to prolonged IBS-PI (Post infectious-IBS). Risk factors for developing IBS-PI include prolonged duration of initial illness, toxicity of infecting bacterial strain, smoking, mucosal markers of inflammation, female gender, depression, hypochondriasis, and adverse life events.
• Serotonin plays a significant role in the control of gastrointestinal motility, sensation, and secretion. Plasma serotonin concentrations are reduced in IBS patients with constipation, but raised in those with diarrhea. especially those showing postprandial symptoms.
• The enhanced stress response, anxiety, and altered cognition found in IBS patients may be due in large part to the influence of their gut microbes. There are several mechanisms by which gut microbes affect the gut–brain–microbiome axis. Via the axis, an altered gut microbiota can send neural signals from the gut to the brain, leading to the heightened stress response and increased visceral hypersensitivity characteristic of IBS. Stress increases intestinal permeability, allowing bacteria and bacterial antigens to cross the epithelial barrier into the bloodstream, inducing an immune response that alters the microbiome.
• Gut microbes also alter the availability of tryptophan, an amino acid required to produce the mood-regulating neurotransmitter serotonin. Gut microbes influence the release of immune system mediators and glucocorticoids (one class of steroid hormone that fight inflammation), which can heighten intestinal pain in IBS.

References

Irritable bowel syndrome: Pathogenesis, diagnosis, treatment, and evidence-based medicine