Definition and Overview
Irritable bowel syndrome (IBS) is a functional gastrointestinal disease characterized by repeated chronic abdominal pain and changes in bowel habits without organic abnormalities. The Rome IV criteria of the International Rome Foundation (Rome Foundation) are used for diagnosis.
The global prevalence is approximately 10-15%, with women being about 1.5-2 times more likely than men, and occurring more frequently in young adults. It has a significant impact on medical costs and quality of life, and the socioeconomic burden, including absenteeism from work and academic disruption, is significant.
Causes and Mechanisms
IBS is a multifactorial disease in which multiple factors interact rather than a single cause.
Gut-brain axis abnormalities
The key mechanism is dysfunction of the gut-brain axis, a two-way communication system between the central nervous system and the enteric nervous system. If abnormalities occur in both the signals coming down from the brain to the intestines (central down-regulation pathway) and the signals going up from the intestines to the brain (vagus nerve path), sensory and motor abnormalities in the intestines appear.
Autonomic dysfunction
Movement and secretion of the digestive tract are controlled by the sympathetic and parasympathetic nerves (vagus nerve). It is known that in IBS patients, inhibition of colonic movement due to overactivation of the sympathetic nerve or hyperactivation due to abnormality of the parasympathetic nerve creates the difference between the diarrhea type and the constipation type. There is a study showing that autonomic imbalance in IBS patients is observed in heart rate variability analysis.
Visceral hypersensitivity
IBS patients perceive normal expansion of the intestines or movement of contents as much more intense pain or discomfort than the general population. The pain processing process of the central nervous system is hypersensitized.
Intestinal dysbiosis
Changes in gut bacterial composition contribute to IBS symptoms by affecting intestinal barrier function, immune response, and serotonin production. The mechanism by which IBS (post-infectious IBS) occurs after infectious gastroenteritis is also related to this.
Other factors
- Serotonin dysregulation: Abnormalities in intestinal serotonin (5-HT) signaling affect intestinal movement and sensory regulation.
- Microinflammation: Microscopic immune activation is observed in the intestinal mucosa in some IBS patients.
- Psychosocial factors: Anxiety, depression, and traumatic experiences contribute to the development and worsening of IBS.
clinical type
According to Rome IV standards, it is classified into subtypes according to bowel habits.
- IBS-D (diarrheal type): More than 25% of stools are soft and watery, and less than 25% are hard.
- IBS-C (constipation type): More than 25% of stools are hard or lumpy, and less than 25% of stools are soft.
- IBS-M (mixed type): Diarrhea and constipation occur alternately.
- IBS-U (Unclassified): Cases that do not fit into the three types.
symptoms
core symptoms
- Abdominal pain: Characterized by abdominal pain associated with defecation. It improves after defecation or appears with changes in frequency and form of defecation.
- Bowel abnormalities: diarrhea, constipation, or alternation of the two. It is accompanied by a feeling of urgency to defecate or a feeling of residual stool.
- Abdominal bloating: Noticeable after eating or eating certain foods.
accompanying symptoms
A significant number of IBS patients also experience fatigue, insomnia, headaches, sexual dysfunction, bladder overactivity, and fibromyalgia. Psychological problems such as anxiety and depression also occur at a high rate.
Warning symptoms (Red flags)
If the following symptoms are present, organic disease should be ruled out:
- bloody or black tarry stools
- fever, weight loss
- First occurrence after age 50
- Family history of colon cancer or inflammatory bowel disease
- Diarrhea with nocturnal awakenings
diagnosis
The diagnosis of IBS is a clinical diagnosis according to Rome IV criteria.
Rome IV criteria: Abdominal pain has occurred more than once a week on average for the past 3 months, and at least 2 of the following 3 criteria are met. 1. Associated with defecation. 2. It is associated with changes in bowel movement frequency. 3. It is related to changes in stool shape (hardness).
Blood tests (CBC, CRP, thyroid function, celiac disease antibodies), stool tests, and colonoscopy may be necessary to rule out organic causes.
treatment
diet
The low FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides, polyols) diet is a non-drug treatment that has been reported to improve overall IBS symptoms in approximately 50-80% of cases in clinical studies. Restricted foods include wheat, dairy products, apples, pears, mangoes, onions, garlic, and beans.
The basic principles are to drink enough water, maintain regular meal times, and avoid overeating.
medication
Treatment medications vary depending on the subtype.
- IBS-D: Antidiarrheal drugs (loperamide), 5-HT3 antagonists (Alosetron), bile acid sequestrants, low-dose antidepressants.
- IBS-C: Osmotic laxatives (PEG), lubiprostone (chloride channel activator), linaclotide (guanylate cyclase activator)
- Abdominal pain: Antispasmodics (butylscopolamine, mebeverine), low-dose tricyclic antidepressants, SSRIs.
Psychological/neurological treatment
There is accumulating evidence that cognitive behavioral therapy, hypnotherapy, and mindfulness meditation are non-pharmacological treatments for IBS. It works towards improving central down-regulation of the gut-brain axis.
If autonomic imbalance is confirmed, autonomic nerve control treatments such as heart rate variability biofeedback, vagus nerve activation training, and transcranial magnetic stimulation can be used as an auxiliary treatment.
probiotics
There are studies showing that some lactic acid bacteria products can help improve overall IBS symptoms, especially bloating and diarrhea, but the effectiveness varies greatly depending on the strain.
life guide
- Maintain regular eating habits. Don't skip meals or overeat.
- Keep a symptom diary to identify specific foods and stressful situations that trigger your symptoms.
- Regular aerobic exercise (30 minutes a day, 5 times a week) helps improve bowel movements and autonomic nervous system balance.
- Lack of sleep worsens visceral hypersensitivity, so sufficient sleep (7 to 8 hours) is important.
- Caffeine and alcohol affect intestinal motility, so keep them in moderate amounts.