Purpose: The purpose of this activity is to examine patients diagnosed with irritable bowel syndrome (IBS) and to facilitate the optimal care of these patients.
Upon completion of this course, the learner should be able to:
- Discuss the incidence and prevalence of IBS.
- Describe the pathophysiology of IBS.
- Discuss the risk factors for the development of IBS.
- Consider current laboratory and diagnostic testing methods for IBS.
- Identify conditions that should be included in the differential diagnosis of IBS.
- Discuss current management and treatment of IBS.
IBS is a "functional intestinal disorder characterized by abdominal pain associated with altered bowel habits" (Vork et al., 2018, p. 1). IBS affects an estimated 15 million people in the US and 7% to 21% of the general population in industrialized nations. Over 50% of gastrointestinal (GI) referrals worldwide are due to IBS. Females are more likely to suffer from IBS than males at a rate of 2:1, and the peak prevalence is between 20 and 39 years of age. Up to 50% of patients have a co-diagnosis of psychiatric abnormalities, with anxiety being the most common (Ferri, 2017). IBS is a frequently diagnosed functional GI disorder that does not result in damage to the GI tract but can significantly decrease the quality of life for those impacted (The National Institute of Diabetes and Digestive and Kidney Diseases [NIDDK], 2017).
Pathophysiology of IBS
The exact underlying pathophysiology of IBS is not fully understood. Consequentially, accurate and non-invasive biomarkers to diagnose, monitor, and evaluate response to treatment are unavailable. Functional GI disorders are related to problems with the brain and GI system working together. These problems can cause increased sensitivity in the GI system and modify the muscle contractions within the bowel. A more sensitive GI system may lead to abdominal pain, bloating, diarrhea, constipation, or both diarrhea and constipation (NIDDK, 2017). Conditions that may be associated with the development of IBS include gastric motility impairment, alterations in fecal microflora or bacteria overgrowth, food sensitivity, inflammation, carbohydrate malabsorption, or increased sensation in response to stimuli (heightened visceral hyperactivity). Some patients may present with an acute onset of symptoms following an infectious illness characterized by two or more of these symptoms: vomiting, diarrhea, fever, or positive stool culture. This post-infective syndrome has been labeled "post-infectious IBS." Increasing evidence indicates that organic disease, which is a physiological change to the tissue not caused by infection of the GI tract, can be identified in some patients who meet the Rome IV criteria for IBS, and a genetic contribution could be likely (Saha, 2014). IBS is sometimes confused with inflammatory bowel disease (IBD), which is much more severe and has many complications (Crohn's & Colitis Foundation, n.d.). See Table 1 for the comparisons of IBS and IBD.
Risk Factors of IBS
The primary risk factors for the development of IBS include:
- a history of stressful life events during childhood or adulthood, including physical or sexual abuse;
- post-traumatic stress disorder (PTSD);
- a severe digestive tract infection;
- a family member with a diagnosis of IBS;
- women under 50 years of age;
- a history of smoking or alcohol abuse;
- a history of chronic pain such as fibromyalgia, chronic fatigue syndrome, or chronic pelvic pain;
- a history of digestive diseases such as gastroesophageal reflux disease (GERD) or dyspepsia;
- a history of mental disorders, including anxiety, depression, or somatic symptom disorder (Epocrates, n.d.; NIDDK, 2017).
Family and job stresses are weak risk factors for IBS but can also lead to symptomatic episodes or exacerbations (Epocrates, n.d.).
Laboratory and Diagnostic Testing for IBS
A symptom-based criteria system for diagnosing IBS was created by the Rome Foundation, which is a group of international specialists focused on functional GI disorders. The initial Rome Criteria I was developed in 1994, with ongoing updates leading to the Rome IV criteria in 2016. The Rome III criteria listed both abdominal discomfort and abdominal pain as critical requirements for this diagnosis, but the Rome IV criteria removed abdominal discomfort, leaving only abdominal pain as the primary requirement. Of further interest, the abdominal pain should occur on at least one day of the week (Vork et al., 2018). A large study by Whitehead and colleagues (2017) noted that these updates to the criteria excluded several patients who were formerly diagnosed with IBS under the Rome III criteria, leading to fewer diagnoses. Further, those who were diagnosed using the Rome IV criteria likely have more severe symptoms and possibly higher prevalence of psychiatric illnesses than previous versions (Whitehead et al., 2017). See Table 2 for the definition of IBS according to Rome IV compared to the Rome III criteria used before 2016.
IBS is typically broken into four categories based on the predominant stool pattern: diarrhea (IBS-D), constipation (IBS-C), a mix of diarrhea and constipation (IBS-M), or undefined predominant stool form (IBS-U). In the updated Rome IV criteria, the IBS subtype identification was revised by only considering the days with symptomatic stools (either loose/watery stools or hard/lumpy stools), rather than an average of all days, which could include normal bowel habits (Vork et al., 2018). See Table 3 for the IBS subtypes and major symptoms.
The Rome IV criteria are the basis for inclusion in IBS clinical trials, cohort studies, and treatment options. The diagnosis is typically made clinically, based on a history of specific symptoms, physical examination, and limited diagnostic testing. In the absence of "red flag" signs such as blood in the stools, unexpected weight loss, chronic severe diarrhea, or a fever, further diagnostic tests are not required. Further diagnostics may be needed based on individual influences such as the presence of stress factors, symptoms, or family history (International Foundation for Gastrointestinal Disorders [IFFGD], 2016). Other forms of testing that may be relevant to the evaluation of IBS symptoms include:
- a complete blood count (CBC) to rule out anemia;
- C-reactive protein;
- stool cultures;
- serology testing for celiac disease, including elevated antibody protein that indicates an immune reaction to gluten, or genetic testing for human leukocyte antigens (HLA-DQ2 and HLA-DQ8);
- colonoscopy imaging in patients with "red flag" symptoms to rule out organic diseases or for patients over 45 years of age;
- consideration of lactose breath testing for lactose maldigestion concerns (American College of Gastroenterology [ACG], n.d.).
Most cases of IBS are diagnosed by a primary healthcare provider with a referral to a gastroenterologist for a more thorough workup based on symptoms. Psychological testing, including screening for anxiety, depression, or other mental health conditions, may be part of the workup if indicated during the initial assessment. A referral to mental health services should be considered as needed (ACG, n.d.; IFFGD, 2016).
Differential Diagnosis of IBS
Symptoms of IBS can appear in other disease conditions. The differential diagnosis would include the conditions listed in Table 4.
Management and Treatment of IBS
The goal of IBS treatment is to improve the patient's quality of life and decrease the severity and frequency of the symptoms. Viera and colleagues (2002) note that a strong therapeutic relationship with a primary healthcare provider is crucial for effective IBS management. A collaborative approach that focuses on diet, mental health, and medication therapy is needed. Dietary management can offer significant benefits for patients with IBS. The patient should be strongly encouraged to maintain a food journal or diary and record symptoms concerning food intake to help identify foods that may contribute to symptoms (Harris et al., 2016; Pimentel, 2018; Viera et al., 2002).
Patients with IBS do not commonly have food allergies; however, they may have food sensitivities. Studies have shown that up to 90% of patients who restrict their diet can improve or eliminate their symptoms (Harris et al., 2016). An elimination diet that removes foods causing symptom flare-ups can be crucial in managing IBS, even though determining the precise food culprit can be challenging. Formal blinded studies note that only 11%-27% of patients can pinpoint the agent stimulating their symptoms (Mayo Clinic, 2017). Some patients report a decrease in symptoms when removing wheat, eggs, coffee, dairy products, yeast, citrus, and potatoes from their diet. While eliminating certain foods from the diet is associated with a decrease in symptoms, skipping meals altogether contributes to worsened symptoms (Harris et al., 2016; Mayo Clinic, 2017; Viera et al., 2002).
Increased fat intake is related to increased stools and diarrhea in most IBS studies. Increased carbohydrate intake is also linked to aggravated symptoms. Carbohydrate sources that are associated with increased symptoms include fructans, galactans, lactose, sorbitol, xylitol, and mannitol (Pimentel, 2018; Saha, 2014). Lactose should only be eliminated in patients with proven lactase deficiency (Viera et al., 2002). These foods are often referred to as FODMAP carbs, which are short chain carbohydrates that are more difficult to digest. FODMAP stands for:
- sugar alcohols
- polyols (Mayo Clinic, 2017; Pimentel, 2018).
These carbohydrates may pass through most of the GI tract without being digested, finally being fermented in the colon, creating hydrogen and contributing to symptoms of gas, bloating, constipation, or diarrhea. Examples of FODMAP carbohydrates include wheat and other grains; garlic; onion; certain fruits; certain vegetables; legumes; sweeteners; dairy such as cottage cheese, cream cheese, ricotta, or yogurt, and beverages such as Chai tea, dessert wine, rum, or coconut water (Rossi, 2017). A low-FODMAP diet is described in Table 5.
Most recommend eliminating all high-FODMAP foods for a few weeks, with obvious relief of symptoms typically seen within a few days. After the initial elimination period, patients can choose to gradually reintroduce some of these foods one at a time to assess tolerance. Many patients benefit from a consultation with a nutritionist or dietitian for additional education and support when attempting a low-FODMAP diet (Gunnars, 2018)
In addition to foods that the patient should avoid, there are several strategies that have been shown to decrease the severity and frequency of symptoms in IBS-D or other subtypes with diarrhea episodes. These include:
- eat slowly
- avoid overeating
- avoid caffeine as it is a stimulant and increases GI motility
- avoid drinking excess water, particularly with meals
- avoid gluten (even for those without celiac disease) in IBS-D
- avoid carbonated beverages that can increase gas content in the stomach and lead to abdominal pain
- avoid chewing gum as it increases the amount of air swallowed
- avoid large quantities of sugar substitutes
- eat frequent, small meals instead of large meals
- limit gas-producing foods such as onions, beans, broccoli, or cabbage (ACG, n.d.; Mayo Clinic, 2017).
In patients diagnosed with IBS-C, dietary fiber is the first-line treatment; a 20- to 30-gram daily intake is suggested to boost stool bulk and facilitate passage. Psyllium and ispaghula husk are associated with improved IBS symptoms over wheat bran. Additional considerations for IBS-C include:
- increased fiber intake;
- avoidance of alcohol and tobacco products;
- consistent intake of probiotic products, which are foods or pills that contain live bacteria, to promote gut health and reduce bloating and gas;
- use of herbal supplements such as peppermint oil or Chinese formulas such as STW5 (ASGE, n.d.).
Peppermint oil has demonstrated efficacy in several small studies. In a study by Cash (2015), enteric-coated peppermint oil (IBgard) was found to reduce abdominal pain, bloating, urgency, and pain at evacuation when compared to the placebo group. This form of peppermint oil (IBgard) is triple coated, allowing a sustained release of the oil into the small intestine and reducing the adverse side effects of previous peppermint oils such as heartburn, abdominal pain, or anal burning (Cash, 2015).
Exercise has been shown to decrease the symptoms of all subtypes of IBS, and physically active individuals have more frequent bowel movements and increased peristalsis. For those with IBS-C, randomized clinical trials have shown a significant reduction in IBS symptoms, particularly with patients participating in 20-60 minutes of moderate to vigorous physical activity three times per week for 12 weeks (Harris et al., 2016). Yoga and other relaxation techniques can be excellent forms of exercise that enhance stress reduction. A qualitative analysis of multiple randomized trials with 273 patients provides evidence that patients performing yoga have significantly reduced IBS symptoms compared to those receiving conventional treatment (ASGE, n.d.; Schumann et al., 2016).
Psychological stress can act as a trigger for IBS and should be managed in a variety of ways. Suggestions include:
- sufficient rest
- relaxation techniques
- deep breathing exercises
- hypnotherapy (Beth Israel Lahey Health, 2019).
Current medication options for IBS-D include alosetron (Lotronex). This 5-HT3 antagonist reduces abdominal pain and bowel movement frequency by slowing peristalsis and reducing pain. It is indicated for females with more severe IBS-D who have not responded to conservative treatments of diet, exercise, and stress reduction. It is typically dosed at 0.5-1 mg PO BID, starting at the lower dose for the first four weeks. Alosetron (Lotronex) is associated with a risk of ischemic colitis and constipation and is therefore currently restricted in the US by the FDA’s risk evaluation and mitigation strategies (REMS). Another drug approved for use in IBS-D is eluxadoline (Viberzi), an opioid-receptor ligand. This drug slows peristalsis and reduces pain. It is contraindicated in patients with alcohol use disorder or anyone who has undergone gallbladder removal due to concern regarding pancreatitis or sphincter of Oddi spasms. The typical dose is 75 mg or 100 mg PO BID. Rifaximin (Xifaxan) is a minimally absorbed broad-spectrum antibiotic that acts in the GI tract to inhibit bacterial transcription and RNA synthesis and is used for IBS-D. The typical dose is 550 mg PO TID for 14 days. If symptoms recur, the treatment course can be repeated for a second 14 days if needed. Serious adverse effects of rifaximin (Xifaxan) include blood or mucus in the stool, persistent diarrhea, or abdominal cramping (ACG, n.d.; Lucak et al., 2017). Antidiarrheals such as loperamide (Imodium AD) have also be used with low success, yet fewer adverse effects. Often, a dose of 2-4 mg up to four times per day is effective for IBS-D. Antidiarrheals can also be used prophylactically during times of increased stress expected to provoke symptoms. The patient should be aware that constipation can result from taking excessive amounts of loperamide (Imodium AD) and other antidiarrheal agents (IFFGD, 2019; Lucak et al., 2017).
Laxatives and stool softeners are the first-line pharmacologic agents to stimulate bowel movements in patients with IBS-C. These medications are inexpensive, and most are sold over the counter. Polyethylene glycol (Miralax, Glycolax) has the highest level of evidence supporting its use compared to other laxatives or stool softeners. Non-digested sugars or sugar alcohol laxatives can increase bloating, and patients tend to be dissatisfied with their adverse effects. A newer group of medications, pro-secretory agents, moisten the stool in the intestine, allowing stool to move through the bowel more easily. Linaclotide (Linzess) is primarily used for adults, and the typical dose is 290 mcg PO daily. It functions by stimulating cGMP production, increasing the secretion of fluid and motility in the intestines. Patients should be warned they could experience severe diarrhea and should stop the medication and increase fluids to avoid dehydration. A second pro-secretory agent, lubiprostone (Amitiza), is FDA-approved for the treatment of IBS-C in women over 18 years of age. The typical dose for IBS-C is 8 mcg PO BID. Lubiprostone (Amitiza) allows more water and chloride to enter the intestine, increases intestinal motility, decreases intestinal permeability, and is helpful for chronic constipation in women for whom other treatments have been ineffective. Common side effects include nausea, diarrhea, and abdominal pain (American Society for Gastrointestinal Endoscopy [ASGE], n.d.).
Antispasmodics can relax the smooth muscle in the intestines and reduce abdominal pain, bloating, or discomfort; they do not improve bowel function and may increase constipation. Commonly used antispasmodics include dicyclomine (Bentyl) and hyoscyamine (Levsin). Dicyclomine (Bentyl) 20 mg is taken PO four times daily, and Hyoscyamine (Levsin) 0.125 to 0.25 mg is taken every four hours as needed. Both function as anticholinergics, antagonizing acetylcholine muscarinic receptors. Common side effects often associated with anticholinergics may occur, including dizziness, blurred vision, and dry eyes as well as constipation (American Society for Gastrointestinal Endoscopy [ASGE], n.d.).
Several types of antidepressants are successful treatment options for all subtypes of IBS. Tricyclic antidepressants (TCAs) can provide global IBS symptom relief, including the associated abdominal pain. Selective serotonin and serotonin/norepinephrine reuptake inhibitors (SSRIs/SNRIs) can reduce pain and provide significant relief in IBS patients (Lucak et al., 2017). See Table 6 for the most common antidepressants used for IBS.
Since mental illness can play a substantial role in IBS, it is crucial to screen patients for any potential mental health concerns and assess/manage them according to the latest evidence (NIDDK, 2017). Patients with comorbid anxiety or depression may benefit from cognitive behavioral therapy and relaxation techniques. Appropriate referrals for treatment should be made, including the consideration of hypnotherapy. Patients with IBS can develop other health conditions in addition to their GI symptoms that may include chronic fatigue syndrome, an inability to manage self-care or work, or chronic pain. Educating the patient on their condition and getting them actively involved in the management of symptoms are essential. An individual with IBS should understand the major aspects of the disorder and the negative impact on their lives and those around them. They should understand their role in managing their symptoms by maintaining a food diary and working with a dietician/nutritionist to develop a nutritional plan that avoids trigger foods. The APRN should educate the patient about current medication options to determine the best treatment options based on their situation. Patients should be aware of current research options and consider exploring options for participation in clinical trials (ASGE, n.d.).
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