Irritable Bowel Syndrome: New Dimensions in Diagnosis and Treatment According to the Latest Scientific Criteria

This article is based on the 2020 review by Prof. Dr. Michael Camilleri, one of the world’s leading experts in gastroenterology and head of the Center for Neurogastroenterology and Hepatology at the Mayo Clinic, USA. His publication “Irritable Bowel Syndrome: Straightening the road from the Rome criteria” offers a comprehensive analysis of the development, challenges, and recent scientific advances related to Irritable Bowel Syndrome (IBS). Prof. Camilleri summarizes the experience of multidisciplinary teams—physicians, researchers, and pharmaceutical experts—who have been working for decades to improve the diagnosis and treatment of this complex functional disorder.

The following questions and answers are designed specifically for patients and their loved ones, presenting the most important and up-to-date knowledge derived from the referenced publication.

“The symptoms and symptom clusters of IBS are non-specific and will never be sufficient for diagnosis on their own – that’s why an individualized approach is key to proper treatment.”

Expert Insights 

Irritable Bowel Syndrome (IBS) is a common functional disorder of the digestive tract that significantly impacts the quality of life for millions of people worldwide. Many patients and their families face confusion surrounding the diagnosis, subtypes, treatment options, and even the very nature of the condition. The reason: the evolving and sometimes controversial diagnostic criteria, known as the “Rome criteria,” which have been developed over the past few decades.

Prof. Michael Camilleri’s scientific review (Mayo Clinic, USA) traces the evolution of these criteria, highlights key scientific questions, and outlines new possibilities for diagnosis and treatment. The following are five leading expert and scientific viewpoints from the publication that can help patients and their families better understand the modern approach to IBS.

1. IBS diagnosis is not based on specific symptoms, but rather a combination of non-specific ones

"Firstly, straightening the road from the Rome criteria should start with the appreciation that the symptoms and symptom clusters are non-specific and are never going to be diagnostic on their own."

Explanation: IBS symptoms—abdominal pain, bloating, diarrhea, or constipation—are not unique to this condition and may be seen in many other disorders. This means that diagnosis is most often made by excluding other, more serious illnesses (called “alarm symptoms”), rather than by identifying a strict set of signs.

2. Strict diagnostic criteria can lead to underestimation and “reclassification” of patients

"The emphasis on pain rather than discomfort and the greater stringency regarding the frequency of pain in the Rome IV definition of IBS have resulted in halving the prevalence of IBS and have led to 'reclassification' of patients from IBS to other functional bowel disorders."

Explanation: With the introduction of stricter criteria in Rome IV (“at least 1 day of abdominal pain per week during the past 3 months”), many patients who were previously diagnosed with IBS now fall into other categories such as “functional constipation” or “functional diarrhea.” This carries the risk that some patients may be denied access to therapies approved specifically for IBS.

3. Separating similar conditions complicates treatment and diagnosis

"An informative example based on a clinical study has questioned the rationale for splitting IBS-D and functional diarrhea, given similarities in clinical and psychosocial characteristics of patients in these 2 entities... leading the investigators to conclude that the 2 entities are in a continuum."

Explanation: Patients with so-called “IBS with predominant diarrhea” and those with “functional diarrhea” often exhibit very similar symptoms and psychosocial traits. This raises the question of whether such separation is justified—especially if the goal is personalized treatment, not merely labeling.

4. In constipated patients, look for signs of pelvic floor dysfunction or anatomical causes

"It is essential to tease out, in greater detail, symptoms that are highly suggestive of rectal evacuation disorders in the appraisal of patients who present with chronic functional constipation, so that such patients may be appropriately investigated and managed."

Explanation: Some patients with chronic constipation actually suffer from rectal evacuation disorders (e.g., pelvic floor dysfunction or anatomical abnormalities), which require a different therapeutic approach—such as biofeedback therapy, not just diet changes and laxatives.

5. Symptom-based diagnosis can be improved through additional testing and mental health assessment

"The diagnostic performance was considerably enhanced by additional history (nocturnal stools, somatization, and affective disorders) and measurements of hemoglobin and CRP. Indeed, individually or in combination, these items enhanced the symptom-based Rome III criteria for IBS..."

Explanation: For a more accurate diagnosis, it is recommended to assess for nighttime diarrhea, somatization symptoms, and signs of depression or anxiety, along with basic blood tests (hemoglobin, CRP). This boosts diagnostic confidence and helps rule out more serious conditions.

Q&A Section

1. How has the diagnosis of IBS evolved over time, and why are there different “Rome criteria”? 

Answer: IBS diagnosis has gone through four major phases using the so-called Rome criteria (Rome I–IV). Each version added or removed specific symptoms or requirements to better identify who truly has IBS. For example, Rome I emphasized abdominal pain related to bowel movements and changes in stool, while Rome IV requires pain to occur at least once a week in the past three months and excludes the term “discomfort” entirely. These changes were meant to clarify the diagnosis, but in practice, they sometimes confused patients and doctors by “excluding” people who suffer but don’t meet the stricter new definitions.

2. Can IBS symptoms change over time, and can the diagnosis change? 

Answer: Yes, IBS symptoms often change over time in the same person. Transitions between different IBS subtypes (e.g., from IBS with diarrhea to mixed IBS) are common, as is shifting to other functional disorders like “functional diarrhea” or “functional constipation.” Even small changes in pain frequency or stool type can alter the diagnosis under current criteria. This shows that these conditions exist on a spectrum, rather than being completely separate entities.

3. Why is mental health considered important in people with IBS? 

Answer: Research shows that IBS patients often experience higher levels of anxiety, depression, sleep disorders, and somatization symptoms. This doesn’t mean IBS is “just in your head,” but rather that mental and physical health are closely connected. Psychological screening is recommended during evaluation, as it can help guide treatment choices and improve quality of life.

4. Are there lab tests that can confirm an IBS diagnosis? 

Answer: In general, IBS is a “symptom-based” diagnosis, meaning it relies primarily on the patient’s reported symptoms and the exclusion of alarm signs. However, lab tests like a complete blood count (hemoglobin), C-reactive protein (CRP), and inflammation markers are used to rule out more serious conditions. These tests don’t confirm IBS, but when normal, they add confidence to the diagnosis when considered alongside the symptoms.

5. What are the new possibilities for diagnosing and personalizing IBS treatment? 

Answer: Modern science offers so-called “actionable biomarkers”—measurable biological markers that can help identify specific physiological mechanisms behind the symptoms (e.g., tests for rectal evacuation disorders, fast or slow gut transit, bile acid malabsorption, etc.). These tests enable more individualized treatment. For instance, if slow gut transit is detected, therapy can target that issue specifically, rather than using a one-size-fits-all approach for all IBS patients.

Conclusion 

Irritable Bowel Syndrome remains both a scientific and clinical challenge—for patients and healthcare professionals alike. Prof. Dr. Michael Camilleri’s publication provides a critical yet constructive perspective on the most important issues surrounding diagnosis, the development of criteria, and individualized treatment for IBS. A clear understanding of symptom dynamics, the mind-body connection, and the potential of modern diagnostic tools opens up new possibilities for effective care and a better quality of life for people living with IBS. The hope is that growing awareness and advancing science will continue to improve how IBS is understood and managed—for the benefit of patients.

Source used: 

Camilleri, M. (2020). Irritable Bowel Syndrome: Straightening the road from the Rome criteria. Neurogastroenterol Motil, 32(11): e13957. doi:10.1111/nmo.13957