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Irritable bowel syndrome (IBS)

Updated : June 20, 2024





Background

Irritable bowel syndrome (IBS) is a prevalent condition affecting the large intestine,  a part of referred to as the colon, causing gastrointestinal disturbances. It is a chronic condition characterized by a combination of abdominal pain, bloating, and changes in bowel habits, such as diarrhea and constipation. IBS is a functional disorder, which means there are no structural abnormalities in the digestive tract that can explain the symptoms. 

The symptoms of IBS can vary widely between individuals and may include abdominal pain or cramping, bloating, gas, diarrhea, constipation, or a combination of both. Some people may also experience urgency in bowel movements or a feeling of incomplete evacuation. These symptoms can be unpredictable and may fluctuate in severity over time. 

 

Epidemiology

  • Prevalence: IBS is a highly prevalent disorder worldwide. The reported prevalence varies depending on the population studied and the diagnostic criteria used. Generally, it is estimated that IBS affects around 10-15% of the global population. It is more common in developed countries compared to developing countries.  
  • Gender: IBS is more common in women than in men. Studies consistently show that the female-to-male ratio is around 2:1, suggesting that females are at a higher risk of developing IBS. The reasons for this gender difference are not entirely understood but may involve hormonal, psychosocial, and genetic factors. 
  • Age: IBS can occur at any age, but it often starts in early adulthood. Studies have shown that the prevalence of IBS decreases with advancing age. However, this could also be attributed to underreporting or changes in diagnostic patterns in older individuals.  
  • Risk Factors: Several risk factors have been associated with the development of IBS. These include a history of gastrointestinal infections, psychological factors such as stress, anxiety, and depression, a family history of IBS, and certain dietary factors. In some cases, IBS can also be triggered by specific events, such as surgery, trauma, or significant life stressors. 

Anatomy

Pathophysiology

  • Altered Gut Motility: One of the primary abnormalities in IBS is the disruption of normal gut motility. The muscles of the gastrointestinal tract contract in a coordinated manner to propel food and waste through the digestive system. In individuals with IBS, these contractions can become either too strong or too weak, leading to irregular bowel movements, abdominal pain, and bloating.  
  • Visceral Hypersensitivity: People with IBS often experience increased sensitivity to pain originating from the internal organs, known as visceral hypersensitivity. The gut of individuals with IBS is more responsive to normal stimuli, such as gas or stool passing through the intestines. This increased sensitivity can result in exaggerated pain signals being transmitted to the brain, leading to the perception of abdominal pain or discomfort. 
  • Intestinal Inflammation: While IBS is not considered an inflammatory disorder like inflammatory bowel disease (IBD), some studies suggest that low-grade inflammation may play a role in its pathophysiology. Chronic inflammation in the gut can affect the normal functioning of intestinal cells and alter the release of certain signaling molecules, such as cytokines, which can contribute to the symptoms experienced in IBS. 
  • Gut-Brain Axis Dysfunction: In individuals with IBS, there is an imbalance in the gut-brain signaling, leading to abnormal gastrointestinal function and visceral hypersensitivity. 
  • Microbiota Dysregulation: The gut harbors trillions of bacteria collectively known as the gut microbiota. These bacteria play a crucial role in maintaining gut health and normal gastrointestinal function. 

 

Etiology

  • Abnormal gastrointestinal motility: One of the primary factors implicated in IBS is altered gastrointestinal motility. Some individuals with IBS may have increased or decreased motility of the intestines, leading to symptoms such as diarrhea or constipation, respectively. 
  • Visceral hypersensitivity: People with IBS often have heightened sensitivity to pain in the gastrointestinal tract. This means that they may experience discomfort or pain at lower levels of distension or stimulation of the intestines compared to individuals without IBS. 
  • Intestinal inflammation: Low-grade inflammation in the intestines has been observed in some individuals with IBS. However, it is unclear whether this inflammation is a cause or a result of IBS symptoms. 
  • Altered gut microbiota: The gut microbiota, which refers to the community of microorganisms residing in the digestive tract, has been found to be imbalanced in some individuals with IBS.  
  • Genetic factors: There is evidence suggesting that genetic factors may predispose certain individuals to develop IBS. Family studies have shown that individuals with a family history of IBS are more likely to develop the condition themselves. 

Genetics

Prognostic Factors

IBS generally has a favourable outlook, and it is unlikely for the diagnosis to undergo significant changes during follow-up. Establishing a positive physician-patient relationship can help decrease the reliance on ambulatory healthcare services among individuals with IBS. 

Clinical History

Age Group:  

  • Irritable bowel syndrome (IBS) can affect individuals of any age group, from children to older adults. However, it is more commonly diagnosed in younger individuals, typically between the ages of 20 and 40. That said, IBS can occur at any age, and there are cases where it has been diagnosed in children and older adults as well. 

Physical Examination

  • Medical History: The healthcare provider will typically begin by discussing your medical history, including your symptoms, their duration, and any relevant family history. They may ask about stress levels, dietary habits, and the impact of symptoms on your daily life. 
  • Abdominal Examination: The doctor will examine your abdomen by gently palpating (feeling) different areas to check for tenderness, bloating, and abnormal masses. They may use varying degrees of pressure to evaluate if it elicits pain or discomfort. 
  • Digital Rectal Examination (DRE): In some cases, a DRE may be performed to assess the rectum and anal canal for any abnormalities, such as hemorrhoids or fissures.  
  • Assessment of Organomegaly: The healthcare provider may palpate other organs, such as the liver and spleen, to check for any enlargement or tenderness, which could indicate other conditions. 

 

Age group

Associated comorbidity

  • Anxiety and depression: There is a strong association between IBS and psychological conditions such as anxiety and depression. The exact relationship is complex and can vary among individuals. Stress and emotional factors can worsen IBS symptoms, and individuals with IBS may experience higher levels of anxiety and depression. 
  • Fibromyalgia: Studies have shown a significant overlap between IBS and fibromyalgia, with a higher prevalence of fibromyalgia among individuals with IBS and vice versa. 
  • Chronic fatigue syndrome (CFS): Also known as myalgic encephalomyelitis (ME), CFS is a complex disorder characterized by extreme fatigue, cognitive difficulties, and other symptoms. There is evidence of an association between IBS and CFS, with a higher prevalence of IBS among individuals with CFS and vice versa. 
  • Gastroesophageal reflux disease (GERD): Some studies have found an increased prevalence of GERD in individuals with IBS, suggesting a possible association between the two conditions. 
  • Inflammatory bowel disease (IBD): While IBD (Inflammatory Bowel Disease) and IBS (Irritable Bowel Syndrome) are separate medical conditions, they do exhibit certain overlapping symptoms, including abdominal pain and changes in bowel patterns. There are cases where individuals may receive diagnoses for both IBD (such as Crohn’s disease or ulcerative colitis) and IBS, but it is crucial to distinguish between the two as their management and treatment methods vary. 

Associated activity

Acuity of presentation

  • Abdominal pain or discomfort: This is the primary symptom of IBS and is often described as cramping or aching pain in the lower abdomen.  
  • Altered bowel habits: IBS can cause changes in bowel movements, such as diarrhea, constipation, or both. Some individuals may experience predominantly diarrhea (IBS-D), while others may have predominantly constipation (IBS-C). Some people may alternate between diarrhea and constipation (IBS-M). 
  • Changes in stool appearance: IBS may cause changes in the appearance of stool. It can range from loose or watery stools to hard and lumpy stools, depending on the subtype of IBS. 
  • Bloating and distension: Many individuals with IBS experience bloating, which is a feeling of fullness or swelling in the abdomen. This can be accompanied by visible distension or a sensation of increased abdominal girth. 
  • Urgency and incomplete evacuation: Some people with IBS may experience a sense of urgency to have a bowel movement, and they may feel like they haven’t fully emptied their bowels even after going to the toilet. 

 

Differential Diagnoses

  • Inflammatory bowel disease (IBD): This includes conditions like Crohn’s disease and ulcerative colitis, which cause inflammation in the gastrointestinal tract. Symptoms can overlap with IBS, but IBD often presents with additional signs such as blood in the stool, weight loss, and fever. 
  • Celiac disease: Symptoms can be similar to IBS, including abdominal pain, bloating, and changes in bowel habits. However, celiac disease is associated with specific antibodies and damage to the small intestine. 
  • Food intolerances: Certain foods or food components may trigger symptoms resembling IBS. Examples include lactose intolerance (inability to digest lactose), fructose intolerance, or sensitivity to FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols). 
  • Endometriosis: In women, endometrial tissue can grow outside the uterus, including the intestines. This can lead to symptoms such as abdominal pain, bloating, and changes in bowel habits, which may overlap with IBS. 
  • Gastrointestinal infections: Certain infections, such as bacterial gastroenteritis or parasitic infections, can cause symptoms similar to IBS. These infections may have an acute onset and may be associated with other signs like fever or recent travel to an endemic area. 

Laboratory Studies

Imaging Studies

Procedures

Histologic Findings

Staging

Treatment Paradigm

Lifestyle and dietary modifications: Making certain changes in lifestyle and diet can often provide relief for IBS symptoms. This may include: 

  • Eating a well-balanced diet 
  • Identifying trigger foods 
  • Eating smaller, more frequent meals 
  • Staying hydrated 
  • Managing stress  

Medications: Medications may be prescribed to manage specific symptoms of IBS. These can include: 

  • Fiber supplements: Supplements such as psyllium can help regulate bowel movements and relieve constipation. 
  • Antispasmodics: These medications help reduce abdominal pain and cramping by relaxing the muscles of the intestines. 
  • Anti-diarrheal medications: These medications may be recommended to control diarrhea symptoms. 
  • Low-dose antidepressants: Certain antidepressants, such as tricyclic antidepressants, can help alleviate abdominal pain and regulate bowel movements in lower doses than those used for depression. 
  • Probiotics: Probiotics may help reduce symptoms in some individuals with IBS, although more research is needed to determine their effectiveness. 
  • Psychological therapies: Given the close connection between IBS symptoms and psychological factors, therapies that address the psychological aspect can be beneficial. These may include: 
  • Cognitive-behavioral therapy (CBT) 
  • Mindfulness-based stress reduction 

 

by Stage

by Modality

Chemotherapy

Radiation Therapy

Surgical Interventions

Hormone Therapy

Immunotherapy

Hyperthermia

Photodynamic Therapy

Stem Cell Transplant

Targeted Therapy

Palliative Care

Behavioural Modifications

  • Low-impact aerobic exercises: Engaging in low-impact activities like walking, swimming, or cycling can help stimulate bowel movements and alleviate constipation. These exercises are generally gentle on the digestive system and can be performed at your own pace. 
  • Yoga: Certain yoga poses, such as gentle twists and forward bends, can also help alleviate digestive discomfort. Look for beginner-friendly or gentle yoga classes that focus on relaxation and flexibility. 
  • Managing stress: Stress and anxiety can worsen IBS symptoms. Engaging in stress-reducing activities like exercise, meditation, and deep breathing exercises can be beneficial. 

Psychological therapies

  • Cognitive-behavioral therapy (CBT): CBT can help individuals manage stress, anxiety, and negative thoughts associated with IBS, thereby reducing symptom severity. 
  • Mindfulness-based stress reduction: Practices such as mindfulness meditation and yoga can help individuals manage stress and improve overall well-being, potentially leading to symptom relief. 

Use of Osmotic laxatives for treating IBS

  • Osmotic laxatives, such as polyethylene glycol (PEG), lactulose, or magnesium hydroxide, are commonly used to treat constipation. While constipation can be a symptom of IBS, the underlying cause of constipation in IBS is often multifactorial and related to abnormal gut motility, visceral hypersensitivity, and alterations in the gut microbiota. 
  • Therefore, the use of osmotic laxatives in IBS is generally limited to individuals who primarily experience constipation-predominant IBS (IBS-C) and have failed to respond to dietary and lifestyle modifications or other targeted therapies 

 

Use of Lubiprostone for treating IBS

  • Lubiprostone is primarily indicated for the treatment of IBS-C in adults. It may be prescribed when dietary and lifestyle modifications have not provided sufficient relief from symptoms such as abdominal pain, bloating, and constipation. 
  • The recommended starting dose of Lubiprostone for IBS-C is 8 mcg twice daily with food and water. The dosage may be adjusted by a healthcare professional based on the individual’s response and tolerability. It is important to follow the prescribed dosage and instructions provided by the healthcare provider. 
  • Clinical studies have shown that Lubiprostone can effectively improve symptoms of IBS-C, including abdominal pain, bloating, and stool consistency. It has been found to increase spontaneous bowel movements and decrease the severity of constipation in individuals with IBS-C. 

 

Use of Guanylate cyclase agonists for IBS

  • Linaclotide: One specific guanylate cyclase agonist that has been investigated for IBS is linaclotide. Linaclotide works by increasing the production of cyclic guanosine monophosphate (cGMP), a signaling molecule that helps regulate fluid secretion and motility in the intestines. By increasing cGMP levels, linaclotide can help reduce the symptoms of IBS, particularly constipation-predominant IBS (IBS-C). 
  • Plecanatide: Plecanatide works by increasing the secretion of fluid into the intestines and accelerating the movement of stool, which helps relieve constipation associated with IBS-C. It activates the guanylate cyclase-C receptor in the lining of the intestines, leading to increased fluid secretion and improved bowel movement. 

Use of Sodium/hydrogen exchanger 3 (NHE3) inhibitor for treating IBS

Tenapanor: Tenapanor belongs to a class of drugs known as NHE3 inhibitors. It works by reducing the absorption of sodium in the intestines, which leads to increased water content in the stool and improved bowel movements. The increased water content helps to relieve constipation, which is a common symptom of IBS-C. 

Use of 5-hydroxytryptamine (serotonin) 4 receptor agonists for treating IBS

Tegaserod: Tegaserod was formerly employed as a pharmaceutical intervention for alleviating symptoms associated with irritable bowel syndrome with constipation (IBS-C). It works by stimulating the movement of the intestines, which helps to relieve symptoms such as abdominal pain and constipation. 

Use of Antidiarrheal agents for treating IBS

Loperamide: Loperamide is primarily used as an over-the-counter medication to treat acute or chronic diarrhea. It works by slowing down the movement of the intestines, allowing for increased water absorption and firming up the stool.

While loperamide can be helpful in managing diarrhea, it is not typically recommended for the treatment of irritable bowel syndrome (IBS) as a standalone therapy. 

Use of Bile acid sequestrants for treating IBS

cholestyramine and colesevelam: 

  • Bile acid sequestrants work by binding to bile acids in the intestines, preventing their reabsorption. This mechanism is primarily used to lower cholesterol levels. However, bile acids also play a role in intestinal function and can interact with receptors in the gut, potentially influencing bowel symptoms. 

Use of 5-hydroxytryptamine (serotonin) 3 receptor antagonists for treating IBS

  • 5-HT3 receptor antagonists, such as ondansetron and alosetron, are primarily known for their anti-nausea and anti-vomiting effects. However, they can also be beneficial in the management of IBS symptoms. These medications work by blocking the action of serotonin at the 5-HT3 receptors in the gastrointestinal tract. 
  • The use of 5-HT3 receptor antagonists in IBS treatment aims to reduce gastrointestinal motility and visceral hypersensitivity, which can help alleviate symptoms such as abdominal pain, bloating, and diarrhea. By blocking the effect of serotonin on these receptors, these medications can modulate the abnormal gut activity seen in IBS. 

 

Use of Eluxadoline for treating IBS

Eluxadoline is a selective agonist of the mu-opioid receptor and delta-opioid receptor, which helps to regulate gastrointestinal motility and reduce abdominal pain associated with IBS-D 

Use of Antispasmodic agents for treating IBS

  • Dicyclomine belongs to a class of medications called anticholinergics, which work by relaxing the smooth muscles in the gastrointestinal tract. It helps to reduce intestinal spasms and cramping, which are common symptoms experienced by individuals with IBS. Dicyclomine is typically taken orally in tablet form, usually before meals. 
  • Hyoscyamine is another anticholinergic medication that works in a similar way to dicyclomine. It helps to relieve gastrointestinal spasms, abdominal pain, and cramping associated with IBS. Hyoscyamine is available in various forms, including tablets, capsules, and sublingual (under the tongue) preparations. 

 

Use of Antidepressants for treating IBS

Tricyclic antidepressants (TCAs): Medications such as amitriptyline and nortriptyline have been shown to provide pain relief and reduce bowel symptoms in some individuals with IBS. TCAs can affect the neurotransmitters in the gut, potentially reducing pain and improving gut motility. 

Use of Antibiotics for treating IBS

In some cases, antibiotics like rifaximin may be prescribed to target the bacterial overgrowth and alleviate symptoms. Rifaximin is a non-absorbable antibiotic that acts locally in the gut, minimizing systemic side effects. However, the evidence supporting the use of antibiotics for SIBO-related IBS is mixed, and not all patients with IBS have SIBO. 

 

Phases of Management

Education and Lifestyle Modifications: Once diagnosed, patients are educated about IBS, its symptoms, triggers, and treatment options. Lifestyle modifications play a crucial role in managing IBS symptoms. This includes dietary changes, stress management techniques, regular exercise, and improving sleep habits. Identifying and avoiding trigger foods or situations is important for symptom control. 

Dietary Modifications: Dietary adjustments are a key part of managing IBS. Patients may be advised to follow specific diets such as the low-FODMAP (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols) diet, which restricts certain carbohydrates that can trigger symptoms. Other dietary modifications may involve increasing fiber intake or avoiding certain types of food, such as spicy or fatty foods. 

Medications: In some cases, healthcare professionals may recommend medications to manage IBS symptoms. The choice of medication depends on the predominant symptoms and may include antispasmodics to reduce muscle spasms, laxatives for constipation-predominant IBS, or medications to address specific symptoms like diarrhea or pain. Probiotics are another option that may be suggested to promote a healthy gut microbiome. 

Psychological Support: Psychological factors, such as stress, anxiety, and depression, can exacerbate IBS symptoms. Patients may benefit from psychological support, including cognitive-behavioral therapy (CBT), which can help manage stress and improve coping strategies. Relaxation techniques, mindfulness, and hypnotherapy are also sometimes used. 

Medication

 

eluxadoline 

100

mg

Tablet

Orally 

Twice a day after meal



belladonna alkaloids/phenobarbital 


Indicated for irritable bowel syndrome (mucous colitis, spastic colon, irritable colon), duodenal ulcer, and acute enterocolitis
1-2 tablets orally three-four times a day
1 tablet (Extended release) orally two times a day; may enhance the dose to three times a day if needed
5-10 ml of elixir orally three-four times a day



mebeverine 


Indicated for Irritable bowel syndrome
135 mg of One tablet orally three times in a day, nearly 20 min prior to meal
Take the tablet with 100 ml of water. It should not chew it
It should not exceed three tablets in a day



alpha-galactosidase, amylase, proteases, lipase and lactase 

One Capsule taken orally along with food



cimetropium 

It is indicated in the treatment of IBS
The recommended usual dose via oral administration is 50 mg three times per day



Dose Adjustments

Limited data is available

ramosetron 

It is indicated for the treatment of IBS
The usual recommended dose via oral administration is 5 mcg one time a day, which should not exceed 10 mcg a day



Dose Adjustments

Limited data is available

hyoscine butylbromide 

Initial dose: 10mg orally thrice daily:

10

mg

oral

3 times a day

Note: The dose may be increased up to 20mg four times a day



clidinium 

In conjunction with other medications, clidinium is used to treat gastrointestinal (stomach and intestines) problems such diverticulitis, irritable bowel syndrome, and others that cause cramps and abdominal pain;
Additionally, it is used to treat peptic ulcer disease, which is characterised by burning in the stomach, fullness in the abdomen, nausea, bloating, etc
In combination: In the US, it (2.5 mg) can only be purchased commercially in a set combination with chlordiazepoxide hydrochloride (5 mg). Individual dosage titration is not possible with fixed-ratio combination medicines; Administration via mouth 3 to 4 times per day



Dose Adjustments

Limited data is available