Clinical practice guidelines for the diagnosis of constipation-predominant irritable bowel syndrome and functional constipation in adults: a scoping review

Abstract

Background

Constipation-predominant irritable bowel syndrome (IBS-C) and functional constipation (FC) are prevalent disorders with overlapping and fluctuating symptoms, which pose challenges for accurate diagnosis. This study aimed to assess the consistency of diagnostic criteria for IBS-C and FC in adults across clinical practice guidelines (CPGs).

Methods

We conducted a scoping review of relevant CPGs by searching electronic databases (MEDLINE and CNKI) and the webpages of Health and Care Excellence (NICE), World Health Organization (WHO), World Gastroenterology Organization (WGO), the American College of Gastroenterology (ACG), American Gastroenterological Association (AGA), Chinese Society of Gastroenterology (CSGE) from Jan 2012 to July 2024. The included CPGs should contain the diagnostic criteria for IBS-C, FC, or both.

Results

We identified 27 CPGs, 14 for IBS-C diagnostic criteria, 9 for FC, and 4 for both IBS-C and FC. The Rome IV criteria were the most commonly applied by the included CPGs (59.3%), followed by the Rome III criteria (22.2%), and pathophysiology classification criteria (7.4%). Abdominal pain was emphasized in IBS-C CPGs (71.4%) but not in any FC CPGs, while spontaneous bowel movement (SBM) frequency was commonly used for FC (88.9%) but not mentioned in any IBS-C CPGs. While 40.7% CPGs acknowledged the similarity between IBS-C and FC, one CPG addressed abdominal pain intensity as a diagnostic criterion, using the 0–9 Likert scale to define painful constipation as a score greater than 4. 71.4% IBS-C CPGs recommended a positive symptom-based diagnosis, versus 11.1% of FC CPGs. Geographical differences were observed, Asian-based CPGs (14.3% of IBS-C CPGs and 11.1% of FC/IBS-C CPGs) recommended stool form type 3 on the Bristol Stool Form Scale (BSFS) and abdominal bloating as diagnostic features. 81.5% CPGs recommended colonoscopy based on alarm symptoms or age.

Conclusion

Inconsistent and regional variations of existing diagnostic criteria for IBS-C/FC were identified. Future improvements should focus on comprehensive characterizations of pain and constipation in both IBS-C and FC. Long-term advancements in understanding the underlying mechanisms, including gut microbiota and related metabolites, are essential for identifying objective biomarkers to improve differential diagnosis and reduce reliance on symptom-based criteria.

Introduction

Constipation is defined by symptoms related to difficulties in defecation, including infrequent bowel movements, hard or lumpy stools, excessive straining, sensation of incomplete evacuation or blockage, and use of manual maneuvers to facilitate evacuation, and primary chronic constipation is not attributed to other disorders or medications [1]. The Rome diagnostic criteria have been used in the field of gastroenterology for diagnosing functional gastrointestinal disorders for more than 30 years, which have evolved through four versions, from Rome I to Rome IV [2, 3]. Based on the presentation of symptoms, Rome criteria further categorize primary chronic constipation into constipation-predominant irritable bowel syndrome (IBS-C) and functional constipation (FC) [3].

For the diagnosis of IBS-C, the Rome IV criteria include recurrent abdominal pain (on average at least 1 day/week) that is associated with at least two of the following three features: change in stool form (> 25% of defecations with hard or lumpy stools and < 25% of defecations with mushy or liquid stools), change in stool frequency, or related to defecation [3]. On the other hand, patients are diagnosed with FC if they have two or more of the following symptoms according to Rome IV criteria: < 3 spontaneous bowel movements (SBMs) per week, straining during > 25% of defecations, sensation of incomplete evacuation in > 25% of defecations, manual maneuvers to facilitate > 25% of defecations, hard or lumpy stools in > 25% of defecations and sensation of anorectal obstruction/blockage in > 25% of defecations. FC patients must also rarely present loose stool without the use of laxatives and do not fulfill the criteria for an IBS diagnosis. A recent epidemiological study revealed that the worldwide prevalence of FC and IBS-C in adults was 11.7% (95% CI 11.4–12.0%) and 1.3% (95% CI 1.2–1.4%) respectively, and the prevalence of these two disorders was varied between different countries/regions [4].

Recurrent abdominal pain and the temporal relationship between pain and defecation are currently the only indicators in the Rome IV criteria to differentiate IBS-C (constipation with abdominal pain) from FC (constipation alone). However, abdominal pain was also reported by FC patients, the severity and frequency of abdominal pain can change over time in both IBS-C and FC patients [5]. The substantial overlap of symptoms in FC and IBS-C is supportive of the notion that they are part of a spectrum rather than separate gastrointestinal motility disorders, which present challenges for healthcare professionals in accurately differentiating between FC and IBS-C and assessing treatment response in both clinical practice and trials [3]. Distinguishing these two disorders from each other is crucial for tailored treatment approaches and the development of new drugs [5,6,7,8,9,10]. Moreover, considering the low diagnostic sensitivity of Rome IV criteria for IBS (62.7%) and FC (32.2%) [11], the uncertainty can impact clinical decision-making, treatment selection, and the evaluation of therapeutic responses in both clinical practice and clinical trials.

Clinical practice guidelines (CPGs) are important for guiding different stakeholders, including clinicians and patients by promoting evidence-based practices. However, CPGs may vary significantly due to a number of reasons such as populations, definitions, and interpretations of the evidence. Identifying consistency between current CPGs could highlight variations in suggested clinical practices and illuminate the future study direction. To date, no study has systematically evaluated the consistency of current CPGs in diagnosing IBS-C and FC. We scoping reviewed the consistency across guidelines, aiming to provide a foundation for future improvements and clearer definitions within the FC-IBS-C diagnostic spectrum.

Methods

The study was presented based on the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) [12]. The checklist was attached in Supplementary File 1. The review protocol could be assessed in Supplementary File 2.

Search strategy

We comprehensively searched MEDLINE (via PubMed) and China National Knowledge Infrastructure (CNKI) databases from January 1, 2012 to July 18, 2024. We also browsed webpages of National Institute for Health and Care Excellence (NICE), World Health Organization (WHO), World Gastroenterology Organisation (WGO), the American College of Gastroenterology (ACG), American Gastroenterological Association (AGA), Chinese Society of Gastroenterology (CSGE). The search terms used, including "constipation," "irritable bowel syndrome," "guideline," "statement," "consensus," and "recommendation," along with their corresponding synonyms, were detailed in the Supplementary File 3.

Inclusion and exclusion criteria

The inclusion criteria were: 1) The title included the terms “constipation/irritable bowel syndrome” and “guideline/statement/consensus/recommendation”; 2) The guidelines were developed by national authorities, international academic associations, or professional administration organizations; 3) Target population was adult (≥ 18 years old); 4) the latest updated CPG version from the same institution. The exclusion criterion: without diagnostic criteria. There was no restriction on language.

CPG selection

Firstly, two reviewers (JYL and WLT) independently screened the titles and abstracts after eliminating duplicates. After that the full texts were reviewed to identify relevant CPGs. Disagreement was resolved by discussing and consulting a third researcher (ZXB).

Data extraction

Two reviewers (JYL and WLT) independently extracted the following data with a standardize data collection form: 1) basic information: title, country/region, organization, year of publication, target disorder, scope of diagnosis or treatment/management; 2) symptomatic diagnosis criteria: applied diagnostic criteria, criteria for abdominal pain frequency/abdominal pain intensity/abdominal pain duration/spontaneous bowel movement/stool form/other symptomatic criteria/onset of symptoms/duration of symptoms, positive diagnosis based on symptomatic diagnostic criteria, and any mention of overlapping definition of IBS-C and FC; 3) diagnostic assessments: lower endoscopy, laboratory tests, imaging tests, colonic transit time test, anorectal test, test for small intestinal bacteria overgrowth (SIBO). This study focused on diagnostic criteria rather than treatment strategies, as diagnosis serves as the foundation for clinical decision-making, while treatment approaches vary widely due to differences in drug availability, healthcare infrastructure, and regional clinical practices.

Data synthesis

We grouped the CPGs by their diagnostic criteria for IBS-C, FC, and both IBS-C & FC. For each group, we conducted a baseline analysis to examine the application of key diagnostic criteria, including stool form, spontaneous bowel movement (SBM) frequency, abdominal pain, and symptom duration. Additionally, we performed specific analyses to assess the overlap between IBS-C and FC diagnostic criteria, identifying CPGs that acknowledged shared features or provided guidance for differential diagnosis. Variability in diagnostic approaches was examined across geographical regions and in the application of diagnostic tests, including lower endoscopy, laboratory tests, imaging tests, colonic transit time test, anorectal test, test for SIBO. The number and percentage of CPGs recommending each diagnostic criterion or test were calculated and presented. Figures summarizing these findings were generated using Microsoft Excel to visually represent the overlap, variability, and regional differences in diagnostic criteria across the included CPGs.

Results

CPG characteristics

The electronic and additional searches resulted in 1320 records. After screening the titles, abstracts and full texts, a total of 27 CPGs between 2012 to 2024 were included. The identification process was shown in Fig. 1. Table 1 details the characteristics of the 27 CPGs included in the review. Of the included CPGs, 14 for IBS-C diagnostic criteria, 9 for FC, and 4 for both IBS-C and FC (references of included CPGs were listed in Supplementary File 4). Included CPGs were from different continents, with 13 from Asia, 8 from Europe and 6 from America. 96.3% included CPGs provided guidance on both diagnosis and treatment/management, with one CPG focusing solely on diagnosis.

Fig. 1

Flow diagram of CPGs identification

Table 1 The characteristics of Clinical Practice Guidelines for functional constipation and/or constipation-predominant irritable bowel syndrome

Application of diagnostic criteria

The Rome IV criteria were the most commonly applied by the included CPGs (59.3%), followed by Rome III criteria (22.2%). 7.4% CPGs applied pathophysiology classification criteria. They classified constipation into normal transit constipation, slow transit constipation and defecatory disorder based on colonic transit time test, anorectal manometry balloon expulsion test or barium/magnetic resonance defecography [13]. Two CPGs (7.4%) applied both Rome III and IV as the diagnostic criteria. One IBS-C CPG from NICE used their own diagnostic criteria including abdominal pain or discomfort, bloating, distension, tension or hardness, change in bowel habit, symptoms made worse by eating, passage of mucus [14]. Details of the recommendations from each CPG could be found in Table 2.

Table 2 Symptomatic diagnostic criteria recommended in clinical practice guidelines for IBS-C, FC, and IBS-C & FC

Overlapped and variability in diagnostic criteria for IBS-C and FC

A common criterion among both IBS-C and FC CPGs was the emphasis on stool form, with 71.43% of IBS-C CPGs and 100% of FC CPGs recommending it as a diagnostic criterion. However, notable variations existed between the two conditions. Abdominal pain frequency was more commonly mentioned in IBS-C CPGs (71.43%) compared to FC CPGs (0%), highlighting a focus on abdominal symptoms in IBS-C. Conversely, spontaneous bowel movement (SBM) frequency was predominantly mentioned in FC CPGs (88.9%), but not in IBS-C CPGs (0%). Additionally, other constipation-related symptoms: such as having over 25% of defecations with at least two of the following: straining, sensation of incomplete evacuation, sensation of anorectal obstruction/blockage, or the need for manual maneuvers to facilitate defecation were more frequently included in FC CPGs (100%) compared to IBS-C CPGs (57.14%). One CPG addressed abdominal pain intensity [15]. The application of symptomatic diagnostic criteria in IBS-C CPGs, FC CPGs and IBS-C & FC CPGs was shown in Fig. 2. 40.7% CPGs discussed the overlapping definition of IBS-C and FC. One CPG proposed a potential solution by utilizing abdominal pain intensity to classify constipation into painful and painless subtypes [15]. A positive symptom-based diagnosis approach (diagnosis only based on symptoms) had been recommended by 71.4% of IBS-C CPGs, 25.0% of FC/IBS-C CPGs and 11.1% of FC CPGs, as opposed to extensive investigations for excluding other conditions. Conversely, 14.3% IBS-C CPGs and 22.2% FC CPGs did not recommend a positive diagnosis approach, emphasizing that organic disorders must be ruled out first.

Fig. 2

Recommendation of symptomatic diagnostic criteria in IBS-C, FC, and IBS-C & FC clinical practice guidelines

Regional variability

14.3% IBS-C CPGs and 11.1% FC/IBS-C CPG from Asia recommended that the Bristol Stool Form Scale (BSFS) type 3 should also be considered as a criterion for constipation, whereas Rome IV criteria define constipation using only BSFS types 1 and 2 [3]. Notably, 42.9% of IBS-C CPGs recommended including abdominal bloating or discomfort without pain as a diagnostic criterion for IBS. Among these, two followed Rome III criteria, four followed Rome IV, and one used its own criteria. Regionally, four were from Asia, one from Europe, and one from America. 78.6% IBS CPGs and 61.5% FC/IBS-C & FC CPGs recommended the criterion for onset of symptoms is at least 6 months, but a IBS CPG from Hong Kong recommended the period from onset of symptoms should be shorter than 6 months [16], and a Canadian IBS CPG and a Hong Kong FC CPG suggested it should be at least 3 months for onset of symptoms [17, 18]. 64.3% IBS CPGs and 69.2% constipation CPGs defined the criterion for duration of symptoms should last at least 3 months.

Diagnostic tests

Figure 3 summarized the recommendations of assessments for diagnosis from IBS-C, FC, and IBS-C & FC CPGs, more details can be found in Supplementary File 5.

Fig. 3

Recommendation of diagnostic assessments in IBS-C, FC, and IBS-C&FC clinical practice guidelines

Lower endoscopy

81.5% CPGs only recommended IBS-C/FC patients with alarm symptoms or signs, or over a specific year of age need to undertake lower endoscopy (sigmoidoscopy or colonoscopy) to exclude the secondary causes. The alarm symptoms or signs in CPGs included visible or occult blood in feces, weight loss for no specific reasons, anemia, family history of colon cancer and acute onset of symptoms at a specific age. The youngest age recommended for endoscopy was 40-year-old from China [19], while other CPGs recommended screening for patients older than 50-year-old.

Laboratory tests and imaging tests

There were 51.9% CPGs recommend basic laboratory tests for IBS-C/FC patients. But the recommended tests were varied between CPGs. A FC CPG suggested only a complete blood cell count is necessary in patients who do not have other symptoms and signs [20], while a IBS CPG suggested a limited number of tests (complete blood count, C-reactive protein, coeliac disease serology, fecal calprotectin and fecal hemoglobin, fasting glucose, thyroid stimulating hormone, calcium levels and ionogram) can be considered in IBS-C patients to rule out metabolic and endocrinologic disorders such as diabetes mellitus, hypothyroidism, hypercalcemia and hypokalemia [21]. But there were 14.3% IBS-C CPGs and 11.1% FC CPGs recommend against routine laboratory tests for the diagnosis of IBS-C/FC. Only one IBS-C CPG recommended ultrasonography to assess intestinal and gallbladder motility patterns and measure segmental contraction frequency in the sigmoid colon [22]. Additionally, one FC CPG recommended imaging tests to rule out organic disorders [23]. 28.6% IBS-C CPGs and one FC CPGs recommended against the routine use of imaging tests.

Assessments for motility

84.6% FC/IBS-C & FC CPGs and 14.3% IBS CPGs recommended colonic transit time tests to diagnose normal transit constipation (NTC) or slow transit constipation (STC). One CPG recommended colonic manometry and gastro-jejunal manometry in STC patients to aid in diagnosing underlying myopathy or neuropathy and guiding decisions on conservative versus surgical treatment [24]. Assessments for the colonic transit time included radiographic studies with radiopaque makers, colonic scintigraphy, indium-marked capsule or wireless motility capsule [15].

Assessment for anorectal function

Anorectal tests were recommended by 42.9% IBS-C CPGs and 76.9% FC/IBS-C & FC CPGs to diagnose the defecatory disorder (DD). The tests included digital anorectal examination, defecography, anorectal manometry and balloon expulsion tests.

Assessment for small intestinal bacteria overgrowth (SIBO)

Three IBS-C CPGs recommended against the hydrogen/methane breath tests to exclude SIBO because of limited supportive evidence, one IBS-C CPG from India recommended using methane breath tests to exclude SIBO in IBS-C patients [25]. None of FC CPG mentioned the methane breath test.

Assessment for visceral sensitivity

One IBS-C CPG recommended using functional magnetic resonance imaging (fMRI) to assess the brain response to rectal balloon distension for visceral hypersensitivity [22]. One FC CPG suggested testing rectal sensitivity by anorectal manometry [24]. The other FC CPG indicated that barostat can be used to evaluate the sensitivity of the rectum or segments of the colon, but it was only for research purpose, instead of clinical practice purpose [26].

Discussion

To the best of our knowledge, this is the first scoping review of the CPGs for diagnosis of IBS-C and FC, inconsistency in diagnostic criteria and recommendation of diagnostic assessment were identified.

Firstly, we found that Rome III or IV criteria were the most commonly applied criteria by CPGs (over 80%), indicating that the Rome criteria were well recognized by most countries and organizations in the diagnosis of FC or IBS-C. The Rome criteria have undergone fourth revisions, which currently serving as the most widely accepted diagnostic framework for FC or IBS-C [3]. A portion of CPGs applied pathophysiology-based classification criteria, which relied on colonic transit time as a diagnostic measure. This classification categorized constipation into normal transit constipation, slow transit constipation, and defecatory disorders based on objective motility assessments, such as colonic transit time test, anorectal manometry balloon expulsion test or barium/magnetic resonance defecography [13]. Only one CPG from the UK (NICE) applied its own diagnostic criteria, incorporating symptoms such as bloating, distension, and dietary triggers [14].

Secondly, around half CPGs discussed the overlapping definition between IBS-C and FC, but most did not elaborate on its implications for diagnosis and treatment. The distinction of IBS-C and FC were developed in the Rome II criteria in 1999 [27]. Patients with abdominal pain related to bowel movements were diagnosed as IBS-C and the lack thereof were diagnosed as FC [28]. It is important to note that IBS-C and FC were defined as two distinct disorders based on questionnaire-based cluster analysis studies and they were mutually exclusive [29]. Ample evidence suggested that abdominal pain in FC patients was common [5,6,7,8,9,10, 30]. In line with this, a novel classification method for constipation, which focused on the intensity of abdominal pain, was proposed [9, 10]. Bouchoucha et al.defined painful constipation as having a score > 4 on a Likert scale of abdominal pain (from 0 to 9 in the past week) and reported that 67% of IBS-C patients and 22% of FC patients were classified into the painful constipation group [10]. However, only one CPG from Spain suggested using abdominal pain intensity to classify constipation into painful and painless subtype [15], and none of the included CPGs addressed the variability of symptoms over time. The overlap between IBS-C and FC presented clinical challenges due to the subjective nature of symptom reporting, particularly abdominal pain. Variability in pain perception, recall bias, and differences in symptom interpretation across cultures and clinical settings contributed to diagnostic uncertainty in real-world practice. These factors complicated accurate classification and treatment decisions, reinforcing the need for clearer diagnostic criteria and clinician awareness of symptom fluctuations over time.

Inconsistencies in diagnostic definitions, low diagnostic sensitivity (IBS: 62.7% and FC: 32.2%) of the most commonly applied critiera (Rome IV) [11] and misclassification of IBS-C and FC could have implications across multiple stakeholders. Clinicians may mismanage FC patients with abdominal pain, as treatment often prioritizes bowel movements over pain relief. Patients may experience reduced treatment effectiveness and quality of life, emphasizing the need to communicate all concerns, including abdominal pain and quality of life, to healthcare providers. Drug developers and regulatory agencies face challenges in defining trial populations, complicating targeted therapy development. Policymakers rely on epidemiological data for healthcare budgeting and resource allocation, which may be skewed by inconsistent diagnostic criteria. Therefore, more objective and comprehensive diagnostic criteria are needed improve diagnosis, treatment outcomes, and healthcare planning.

Thirdly, the current symptomatic criteria for IBS-C and FC in CPGs have certain limitations. The criteria for IBS-C lacked constipation-related criteria, particularly the frequency of bowel movements. Rome criteria simplified the multiple criteria of constipation in IBS patients by using only stool form to make diagnosis easier [31]. However, this change lacked rigorous clinical evidence [31] and not useful in clinical trials for drug development as the FDA clinical trial CPG for IBS-C included the criterion for the frequency of bowel movements [32]. The criteria for FC lacked abdominal pain-related criteria. As abdominal pain was also reported in FC patients, but if the frequency of abdominal pain was less than 1 time per week, such patients would not be classified as IBS-C. Therefore, the lack of pain related criteria in FC patients may lead to this symptom being overlooked in clinical treatment as well as in the development of new drugs. Additionally, the diagnostic criteria for abdominal pain in patients with constipation only considered frequency and did not include criteria for intensity to evaluate severity. To assess severity, other methods such as questionnaires (e.g., IBS Symptom Severity Scale (IBS-SSS) [33] and Patient Assessment of Constipation-Symptoms (PAC-SYM) [34] were needed. Furthermore, assessing abdominal pain from different dimensions might also have value, as a recent cross-sectional observational study found that IBS-C patients experienced more bothersome, frequent, and diffuse abdominal pain compared to other IBS subtypes [35].

Besides, the results of this study indicated there are some specific diagnostic criteria for IBS-C and FC vary across different regions and ethnics. CPGs from Asia, for instance, placed greater emphasis on abdominal discomfort and bloating as important diagnostic criteria for IBS, rather than abdominal pain alone. Definition of abdominal discomfort and abdominal pain were subjective, and Asian patients more commonly described bloating and discomfort than pain [36]. Moreover, in Asia, particularly in India, BSFS type 3 was also recommended as a diagnostic criterion for constipation. A study from Thailand suggested that BSFS type 3 is associated with constipation [37], and a constipation CPG from India recommended that stool forms were softer in India compared to Western regions [25]. However, to develop criteria for different regional populations, the threshold for symptom frequency and duration needs validation in diverse regions. Besides, the subjective expression of symptoms by patients may be influenced by different cultures and language habits, for example, abdominal discomfort represents a deviation in different languages, which was one of the reason that Rome IV removed the term “discomfort” from the definition of IBS [11].

Another key discrepancy across CPGs related to diagnostic testing approaches. While most of the CPGs recommended positive diagnostic strategy to reduce excessive testing for IBS-C, the majority of FC CPGs did not mention this approach. Traditional diagnostic approach for functional disorders was to exclude other conditions, which led to patients being subjected to excessive testing. A positive diagnosis strategy involved a careful history, physical examination, and the use of a standard definition to make a diagnosis without the need to perform extensive investigations. Many studies of IBS indicated that a positive diagnostic strategy was non-inferior to a diagnosis of exclusion [38, 39]. A positive diagnosis not only saves the resources for extra assessments but can also substantially reduce the time to appropriate treatment. Although most CPGs recommended against using colonoscopy as routine test for constipation, few studies revealed the difference between positive diagnosis strategy and diagnosis of exclusion for FC. Recommendation of positive diagnosis of FC requires more evidence.

Interestingly, a contradiction existed between the adoption of Rome IV’s symptom-based approach and the continued recommendation of diagnostic procedures in certain CPGs. In all included IBS-C CPGs, only Japan recommended colonoscopy regardless of alarm symptoms or age [22], reflecting the country’s health policy and clinical training, which emphasize early colorectal cancer screening [40]. Similarly, two FC CPGs (Germany and China) recommended colonoscopy to rule out organic disease [23, 41], likely due to differing healthcare priorities and concerns over misdiagnosis. The persistence of diagnostic testing despite Rome IV's recommendations might also be influenced by healthcare infrastructure, clinician training, and regional disease prevalence. Countries with well-funded public health systems might have greater capacity to perform routine colonoscopies, whereas resource-limited settings may favor symptom-based diagnosis due to cost constraints. In settings where colorectal cancer or other organic conditions are of higher concern, clinicians may favor a more cautious, test-based approach. Medico-legal concerns and defensive medicine drive increased diagnostic testing in some regions to avoid malpractice claims, whereas cost-conscious healthcare systems prioritize symptom-based diagnosis [42]. Future updates to CPGs should provide clearer risk stratification criteria for when additional testing is warranted, ensuring a balance between minimizing unnecessary procedures and safeguarding against missed diagnoses.

It is notable that there was no diagnostic biomarker for IBS-C and FC in all CPGs, which indicated that this spectrum of diseases is still grouped together by symptoms with unclear pathological mechanisms. Assessments for the known pathophysiology of constipation were recommended in most FC CPGs. However, only one IBS CPG [22] and one constipation CPG [24] recommended visceral sensitivity test for IBS-C/FC patients. Even most CPGs acknowledged that visceral hypersensitivity was the key factor of abdominal pain, rare CPGs recommended testing visceral sensitivity in clinical practice. With limited clinical evidence and inconvenient testing method for visceral sensitivity, there was still a lack of objective criteria for the assessment of abdominal pain in clinical practice. Although CPGs did not recommend any biomarkers for IBS-C/FC, emerging evidence suggested that certain biomarkers such as serotonin, gut microbiota, and their metabolites could be potential in distinguishing between these conditions and improving diagnostic accuracy, as they might play important roles in pathophysiology of IBS-C/FC [6, 43,44,45,46,47,48,49].

While this review primarily focused on diagnostic criteria, diagnosis is closely tied to treatment strategies. This study highlighted that effective management of both FC and IBS-C should take a more comprehensive and patient-centered approach, addressing not only bowel movement frequency and stool consistency but also abdominal pain intensity and frequency, the severity of constipation-related symptoms, and overall quality of life. A more holistic treatment strategy that considers these factors can lead to better symptom control, improved patient satisfaction, and enhanced long-term outcomes. In addition, both IBS-C and FC are chronic disorders with symptoms fluctuating over time [5], which posing a challenge for long-term disease management. Effective treatment requires a flexible and personalized approach tailored to symptom variability. Clinicians must adapt management strategies to address changing symptoms, ensuring that both bowel function and abdominal pain are appropriately managed. Furthermore, patients' perceptions of their symptoms and diagnosis influence their treatment adherence and overall satisfaction, making it essential for CPGs to incorporate patient-centered considerations in diagnostic frameworks.

This review has several limitations. Considering the update frequency of CPGs, we only included CPGs from the last decade (2012–2024) in the article. As new evidence continues to emerge, the CPGs included at different periods can only make recommendations based on the evidence available at that time. Second, the review may be subject to publication bias, as CPGs that are more rigorously developed or updated may be more likely to be published and indexed in the databases searched. This review focused exclusively on CPGs, potentially overlooking valuable insights and evidence from primary research studies or systematic reviews that are not encapsulated in guideline documents. In addition, this review did not assess the methodological rigor of CPGs, which vary in quality and evidence strength. This review analyzed regional differences in diagnostic criteria descriptively, as the small sample size of included CPGs limited the feasibility of statistical testing. Future studies with a larger dataset could explore statistical comparisons to assess the significance of regional variations. This study may not include CPGs from private organizations or regional medical societies that have not been published in the searched databases, which could limit the diversity of perspectives or practical insights on IBS-C and FC diagnosis. In addition, only including the latest version of each guideline may introduce bias, as older versions could provide insights into evolving diagnostic practices and trends.

Future directions

In the short term, conducting more comprehensive evaluations of abdominal pain in patients with IBS-C/FC is essential. This should involve assessing the frequency, intensity (using a 0–9 Likert scale and defining painful constipation as > 4), bothersomeness, interference with daily activities, localization, and anatomic distribution of abdominal pain. Additionally, evaluating the frequency of bowel movements and defecation-related symptoms is necessary for patients with IBS-C. It is also important to develop symptom definitions and thresholds that consider regional, cultural, and linguistic differences. These measures will enhance the specificity and sensitivity of the diagnostic criteria based on symptomatic presentation, leading to improved characterization of IBS-C and FC.

In the long term, a better understanding of the mechanisms of pathophysiology is needed to establish biomarkers for objective assessment and early detection of risk factors. Multi-omics data, including phenome, microbiomes, metabolomes, and brain connectomes, are crucial for unravelling the mechanisms underlying the spectrum of IBS-C and FC [50, 51]. Specific metabolites such as secondary bile acids, short-chain fatty acids, serotonin, tryptophan, and methane are particularly important as they are related to intestinal sensory, motor, and secretory functions. Integration and analysis of these different omics using machine learning methods such as the Data Integration Analysis for Biomarker Discovery (DIABLO) can facilitate biomarker discovery and provide insights into the complex interactions across the disease spectrum [52].

Given the dynamic nature of abdominal pain in both IBS-C and FC patients, longitudinal studies with well-defined metadata are valuable in controlling for interindividual confounding variables and exploring the underlying mechanisms, especially the role of gut microbiota and their metabolites, of abdominal pain in patients with constipation [53]. These studies may lead to a shift in clinical practice and future research towards a more personalized and effective approach to the diagnosis and management of constipation. Additionally, considering the action mechanism of treatments can help identify potential biomarkers.

Conclusion

This scoping review of CPGs for the diagnosis of IBS-C and FC provided valuable insights into the overlapping definitions, current limitations, regional variations, and future directions in this field. To improve the diagnostic criteria, a short-term strategy involves implementing more comprehensive assessments and considering regional and cultural differences in symptom definitions. In the long term, a better understanding of the pathophysiological mechanisms in multi-omics along with the use of machine learning techniques, can significantly contribute to the diagnosis and management of constipation.