diagnosis and treatment of IBS from bench to bedside

diagnosis and treatment of IBS from bench to bedside

September 17, 2024 Posted by By Charles


IBS diagnosis and treatment based on predominant symptom: from bench to bedside.

IBS Days 2024 included a postgraduate course with practical talks discussing clinical cases of patients with IBS or functional dyspepsia who present with a wide range of burdensome digestive symptoms. Jan Tack, MD PhD, from the University of Leuven, shared good practice for clinicians on how to conduct an effective clinical history and symptom assessment. The first step is listening to the patient’s concerns face to face with the patient, an opportunity that has decreased over time due to the provider’s time restraints. An IBS-specific history, including dietary habits, alarm symptoms, and associated disorders of gut-brain interactions and psychosocial co-morbidities, is also useful.

Cesare Cremon, MD, from Policlinico di sant Orsola-Mapighi Hospital in Bologna (Italy), gave an overview of the dos and don’ts associated with the currently available diagnostic tests for diagnosing IBS based on UEG/ESNM, BSG, ACG, AGA, and Italian guidelines. Full blood count, C-reactive protein, celiac serology, and fecal calprotectin are indicated in patients with symptoms compatible with IBS without alarm features. If diarrhea is the predominant symptom, a colonoscopy with biopsies should be considered to rule out microscopic colitis. Additional diagnostic tests to consider in selected patients are imaging studies, anorectal manometry in patients with symptoms suggestive of a pelvic floor disorder not responding to therapy, stool testing for Giardia in endemic areas, and testing for bile acid malabsorption.

 

What do the guidelines say on screening tests for an accurate diagnosis of IBS? Source: Cesare Cremon’s talk at IBS Days 2024.

 

Johann Hammer, MD, from the Medical University of Vienna, highlighted that diarrhea and distension may occur after consuming carbohydrates even though malabsorption is absent. One of the factors involved is an altered gut microbiome. SIBO measurement with breath tests has limited value in IBS, and advanced informatics and high-throughput sequencing may offer value for detecting dysbiosis in patients with disorders of gut-brain interaction (DGBI) based on the rationale that small intestinal dysbiosis, but not SIBO, emerges as a cause of clinical symptoms. It is also important to bear in mind that treatment decisions on the basis of malabsorption measurements alone are of limited value in clinical practice. In contrast, symptom measurement through valid and unbiased questionnaires (i.e., pediatric Carbohydrate Perception Questionnaire and adult Carbohydrate Perception Questionnaire) is more clinically relevant in patients with carbohydrate malabsorption syndromes.

 

Valid carbohydrate perception questionnaires are more clinically relevant than breath tests for diagnosing carbohydrate intolerance. Source: Johann Hammer’s talk at IBS Days 2024.

 

The second part of the post-graduate course consisted of lectures addressing pharmacological and non-pharmacological treatments for managing abdominal pain, bloating, constipation, and diarrhea in IBS patients. Maura Corsetti, MD, PhD, from the University of Nottingham, covered recent data supporting non-pharmacological (low FODMAP and Mediterranean diet, peppermint oil, and brain-gut behavior therapies) and pharmacological interventions (antispasmodics) in IBS. Patient baseline beliefs can affect the placebo response’s magnitude, timing, and persistence. Nocebo effects can influence the rate of reported adverse events in trials and neuromodulators in IBS and reassuring the patient about the number of patients who do not report side effects after the treatment (positive framing) may lead to less reporting of side effects.

 

Placebo responses in patients with IBS. Source: Maura Corsetti’s talk at IBS Days 2024.

 

Chloé Melchior, MD, PhD, provided updates on the management of abdominal bloating in IBS, a prevalent symptom in patients with IBS with constipation (IBS-C) and IBS with alternating bouts of constipation and diarrhea (IBS-M). A good practice is to start by first treating constipation if it is bothersome, and biofeedback therapy and breathing techniques can also be considered in cases of refractory constipation that may be related to an abnormal contraction of the diaphragm and abdominal wall relaxation (abdomino-phrenic dyssynergia) rather than excess gas. A low FODMAP diet under the supervision of trained dietitians can be considered in order to address food-related bloating.

 

Treatment targeting bloating in IBS. Source: Chloé Melchior’s talk at IBS Days 2024.

 

Regarding treating constipation in IBD-C, Carmelo Scarpignato, MD, MPH, PharmD, from the United Campus of Malta, highlighted that beyond managing constipation, it is important to address intestinal discomfort and correct dysbiosis that is often present in patients with IBS-C and evaluate if the patient is taking medications associated with constipation (e.g., opioids, anticholinergics, tricyclic antidepressants, non-steroidal anti-inflammatory drugs, and iron supplements). Dietary fiber is the first-line treatment for constipation. Two green kiwifruits daily may work better than psyllium to increase spontaneous bowel movements and improve gastrointestinal comfort in constipated patients. One in every four patients is satisfied with pharmacological treatments for IBS-C, which include laxatives (e.g., macrogol, widely used in Italy) and secretagogues (e.g., linaclotide and tenapanor, widely used in the USA). Some probiotics may slow transit time, which is associated with improvements in stool form and frequency, and rifaximin has shown a potential eubiotic effect worth considering in the management of constipated patients. Transcutaneous electrical acustimulation and abdominal massage may also improve colonic transit time in patients with IBS-C.

 

Currently available strategies for modifying gut microbiota and correcting dysbiosis. Source: Carmelo Scarpignato’s talk at IBS Days 2024.

 

Brian Lacy, MD, PhD, FACG, from Mayo Clinic, reviewed current therapies for treating diarrhea in patients with IBS. Diet is a reasonable first choice in patients with IBS-D. The low FODMAP diet is one of the most researched diets for IBS, and 50% to 80% of patients report some benefits compared to consuming a regular or habitual diet. However, it is not easy to follow, many patients struggle to keep to the diet, it requires extensive counseling, and vitamin and micronutrient deficiencies can occur over the long term. The benefits of a low-gluten diet for IBS are unclear and fructans rather than gluten are the culprit for most patients. Although following the Mediterranean diet (MED) did not show a direct correlation with the severity of IBS symptoms, some MED foods may exacerbate IBS symptoms. Therefore, it is necessary to customize the MED for individuals with IBS.

Tricyclic antidepressants are a valuable supplement in individuals with IBS-D due to their low cost, long track record of efficacy, capacity to help with diarrhea due to anticholinergic effects, and alleviation of visceral and central pain and psychological distress. In primary care, second-line IBS therapy with amitriptyline reduced symptoms at 6 months.

Certain probiotics may help relieve global IBS symptoms (moderate certainty), while there is less certainty about their effectiveness for alleviating abdominal pain and bloating. Complementary and alternative therapies, supported by at least one intervention human trial in IBS, include glutamine for post-infectious irritable bowel syndrome, peppermint oil to relieve global IBS symptoms, Iberogast, gut-directed psychotherapies, and Gelsectan. Ashe therapeutic efficacy of a single treatment is insufficient, an augmentation therapy combining various treatments is worth investigating.

 

Summary of nutrition and medical treatments for diarrhea in patients with IBS. Source: Brian Lacy’s talk at IBS Days 2024.

 

In addition to 12 oral presentations in which renowned scientists worldwide updated the latest discoveries in IBS, three parallel workshops and free paper sessions addressed new advances in gut microbiome-targeted treatments for IBS, the clinical approach to abdomino-phrenic dyssynergia and anorectal disorders overlapping with IBS, and the pathophysiology of IBS. In addition, 58 poster presentations were displayed during the conference, covering basic, translational, and clinical science in IBS.

 

References and recommended reading:

  1. History and symptom assessment in IBS:

 

  1. Diagnostic tests for IBS:

 

  1. Treatment of IBS

Placebo and nocebo effect in patients with IBS:

 

Treatment of abdominal bloating and distension:

 

Treatment of IBS with constipation:

 

Treatment of IBS with diarrhea:





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