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Toward a Positive and Comprehensive Diagnosis of Irritable Bowel Syndrome

Yehuda Ringel, MD, and Douglas A. Drossman, MD, University of North Carolina, Chapel Hill

[Medscape Gastroenterology 2(6), 2000. © 2000 Medscape, Inc.]

Introduction

Background

Irritable bowel syndrome (IBS) is one of the most frequently diagnosed disorders in general population and medical settings. It accounts for an estimated 28% of patients seen in gastroenterology practice and up to 12% of patients seen in primary care practice. IBS affects about 10% to 20% of adolescents and adults (14% to 24% female, 5% to 19% male) in Western countries. The disorder can substantially impair the patient's quality of life and increase annual healthcare costs; it poses a considerable socioeconomic burden on the healthcare system overall.[1-3] The high prevalence and significant sequelae of IBS have led to increased interest in this disorder among clinicians, clinical investigators, basic scientists, physiologists, and mental health professionals.

Indeed, over the last 2 decades there has been a 10-fold increase in citations on IBS.[4] The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and various gastroenterologic societies have increased the exposure of IBS through educational and research programs. Most recently, the pharmaceutical industry has begun international marketing campaigns related to new enteric receptor agents. Nevertheless, the etiology and pathogenesis of IBS still are not completely characterized, and no unique morphologic, physiologic, or pathologic pattern that can serve as a marker for the disorder has been identified. Such circumstances where an illness exists without a defined disease create certain diagnostic dilemmas for the clinician: (1) Is IBS a genuine disorder, with clearly definable determinants? (2) How can the diagnosis be made in the absence of a biological marker? (3) How confident can the clinician be in making the diagnosis?

A Change in Thinking

During the last 20 years, significant changes have occurred in how we conceptualize IBS. This has enabled the clinician to better address these dilemmas and has led to the acceptance of IBS as a discrete clinical entity that can be diagnosed and treated in a positive and empiric manner.

Two important processes have led to this change.[4] First, there has been a movement toward understanding chronic medical disorders such as IBS as integrated, multidetermined conditions with varying clinical features, based on biopsychosocial models of illness and disease.[5-7] Second, recent expansion and refinement of investigative methods have enabled us to study the various determinants (physiologic, psychological, and social) that underlie this disorder, its clinical expression, and outcome. Some examples include the use of standard psychological measures/instruments, the electronic barostat, and functional brain imaging by positron-emission tomography (PET) and functional magnetic resonance imaging (fMRI).

These processes have allowed us to sort out the mechanisms by which physiologic, psychological, behavioral, and environmental factors interact simultaneously as well as at multiple levels to characterize IBS. The relative contributions of these factors vary between patients or in individual patients over time and determine the severity of the symptoms and the overall clinical presentation. This understanding helps to explain the existence of severe symptoms in the absence of (or lack of correlation with) any significant physical or physiologic findings or even the presence of major physiologic disturbances in the absence of symptoms.

The development of symptom-based criteria permits a focus on the patient and his/her illness experience, which is derived from the biopsychosocial determinants. These criteria also help to standardize diagnostic and treatment approaches and selection of patients for clinical trials. (A more detailed presentation of the relation of psychosocial factors with the pathogenesis and clinical expression of IBS and the biopsychosocial model can be found elsewhere.[6,8])

This article presents a patient-centered, comprehensive approach to the diagnosis of IBS using symptom-based diagnostic criteria. It also addresses ways to integrate physiologic and psychosocial factors into the diagnostic plan to help the clinician achieve a confident diagnosis in a cost-effective manner.

The Clinical Presentation of IBS

The diagnosis of IBS is determined by certain symptom clusters that "breed true" as a distinct clinical entity. The evidence for and features of these specific symptoms are discussed below.

Presentation of Symptoms

The most frequently reported symptom in IBS is pain or discomfort in the abdomen.[9,10] This pain often is poorly localized and may be migratory or variable in nature, and is usually relieved with defecation, thus supporting a primary colonic origin for this symptom. It is also associated with a change in the consistency or frequency of stools and with altered bowel habits (ie, diarrhea, constipation, or combination of both at varying times).[3,11,12] Other symptoms -- including bloating, urgency, or the feeling of incomplete evacuation -- are present frequently, again suggesting colonic dysfunction.

Although IBS symptoms often occur in clusters[13]; some of the symptoms may occur sequentially and may vary in kind, location, and severity over time.[9] The frequency of IBS episodes also varies greatly among patients. While some patients may have daily episodes or continuous symptoms, others experience long symptom-free periods.[9] These patterns raise the question as to when someone has IBS as opposed to occasional bowel complaints that may be considered a part of the normal response of the bowel to stress.[14] For the most part, the characterization of IBS as a "disorder" is determined by certain frequency guidelines developed from epidemiologic and clinical studies.[4]

A subgroup of patients with IBS also complain about other (ie, noncolonic) gastrointestinal (GI) symptoms, such as heartburn, nausea, and early satiety. Furthermore, significant overlap has been reported between IBS and other functional GI disorders (eg, functional dyspepsia, functional heartburn, proctalgia fugax),[15-18] with, as mentioned earlier, an individual's primary symptoms shifting over time.[17] Patients with IBS have other (ie, non-GI) symptoms and therefore visit their primary care physician quite often for both GI and non-GI complaints.[2,19] The non-GI symptoms include fibromyalgia[20-23] and other musculoskeletal symptoms,[20] headache, genitourinary symptoms,[24] sexual dysfunction,[25] sleep disturbances,[26,27] and chronic fatigue.[3]

These findings are consistent with IBS involving dysfunction of both the central and peripheral nervous system (ie, a "brain-gut disorder"). There may be a peripheral (ie, visceral) basis for some GI symptoms due to dysfunction of the enteric nervous system in the upper as well as the lower gut. In addition, and particularly for patients with higher levels of psychosocial distress or psychological comorbidity, there may be central upregulation of peripheral (both somatic or visceral) signals based on central nervous system (CNS) hypervigilance or hypersensitivity.

Furthermore, not only can IBS symptoms be varied and multiple, but they may also coexist with or be initiated by other organic disorders (ie, ulcerative colitis or Crohn's disease).[28] Sometimes, therefore, it is difficult to determine whether the patient's symptoms are due to an organic (eg, inflammatory bowel disease [IBD]) or functional (eg, IBS) condition. From a biopsychosocial perspective, deciding whether a symptom is "functional" or "organic" is not as important as determining which factors need further attention.

Finally, it should be noted that while the symptoms described above help characterize the diagnosis of IBS, other types of symptoms or demographic and temporal features may help to exclude yet other disorders and direct the extent and nature of treatment. For example, symptoms that awaken the patient from sleep, present first at an older age, or manifest as GI bleeding, weight loss, or fever are regarded as alarm signs (also called "red flags"), and their presence should lead to further investigation.[3,11,12]

Psychosocial Influences on Symptom Presentation and Outcome

In keeping with the above concepts, patients with IBS have an increased prevalence of comorbid psychosocial disturbances.[3,8] The presence of psychosocial factors is associated with higher symptom severity and poorer outcome.[19,29-34]

In a recent study, we compared physiologic, psychosocial, and health status measures between patients with moderate and severe IBS[31] and found that pain reports relate more to psychosocial factors (eg, depression, coping style, and illness behaviors) than to physiologic factors (ie, rectal sensitivity). Moreover, healthcare utilization (as determined by number of physician visits, phone calls, and days in bed), and quality of life were also highly influenced by psychosocial factors.[33]

These findings indicate that for patients with IBS, psychosocial factors prominently influence symptom frequency, severity, overall health status, healthcare utilization, and clinical outcome. This can explain the higher frequency of more severe psychosocial difficulties, including major loss[35,36] and abuse history,[37] in IBS patients seen at referral centers and among patients who seek medical care/attention often.[3,38]

By contrast, the psychosocial features of individuals with IBS who do not seek healthcare are not different from those of the general population.[38-40] By influencing symptom experience and illness behavior, psychosocial factors affect the clinical expression and outcome of patients with IBS. However, because IBS is defined by symptoms and because psychosocial factors vary in their features across populations with the same symptoms, psychological factors are neither included in the diagnostic criteria for IBS nor support its diagnosis.

The Diagnosis

Symptom-Based Criteria

The use of symptom-based criteria allows the physician to make a "positive diagnosis" of IBS, thereby reducing the need for excess diagnostic tests/studies to exclude other conditions. These criteria also serve to legitimize the disorder to patients and physicians. However, developing diagnostic criteria is challenging because of the absence of specific physical or biochemical findings, the variability of the symptoms (with regard to pattern, location, and severity) among patients -- and even in the same patient over time, and the inconsistency of the clinical course. Several symptom-based diagnostic approaches for IBS have been proposed over the last 2 decades in an attempt to standardize the diagnosis and increase its specificity. These criteria were selected through use of clusters of symptoms thought to be consistent with the disorder.[11,12]

In a study done 20 years ago, 6 symptoms were identified that differentiate between patients with irritable bowel from those with organic intestinal diseases.[41] These symptoms, later known as the "Manning criteria," for the first time suggested the feasibility of a positive diagnostic approach to IBS based on symptom criteria. Although widely used in epidemiologic and clinical studies, these criteria have been of limited clinical value in differentiating IBS from organic, lower GI tract diseases.[42] Nevertheless, they have provided the basis for the more recent "Rome criteria," first published for IBS in 1989[43] and for all of the functional GI disorders in 1990.[10]

The Rome criteria. The Rome criteria were first developed by international consensus ("Delphi" approach). These multinational working teams also critically reviewed the literature on the epidemiology, pathophysiology, diagnostic approach, and treatment for IBS and other functional GI disorders. The original criteria (ie, "Rome I")[44] have recently been revised ("Rome II") and published as a book[3] and journal supplement.[45] The Rome II criteria for IBS are shown in the Table below. Over the 20 years since publication of the Manning criteria, the use of symptom-based criteria for the diagnosis of IBS has become accepted as the diagnostic standard for research and clinical care.

According to these criteria, the presence of abdominal pain/discomfort is required for the diagnosis of IBS. The pain or discomfort must be associated with at least 2 of the 3 criteria that link the pain to change in bowel habit (see Table). Therefore, pain/discomfort alone, or with only 1 of the 3 criteria, or the existence of altered stool habit (ie, frequency or stool form) without pain/discomfort is not sufficient for the diagnosis of IBS. Patients may have other functional bowel symptoms that do not fulfill the criteria for IBS. These symptoms may represent different functional bowel diagnoses, such as functional abdominal pain, functional constipation, functional diarrhea, functional abdominal bloating, or unspecified functional bowel disorder.[3]

The Rome criteria also require certain temporal features for the diagnosis. Symptoms must be present "at least 12 weeks or more, which need not be consecutive, in the preceding 12 months," and this can apply to any 12 weeks in a year. Thus, symptoms need not be consecutive, and the chronicity criterion can be fulfilled even if the symptoms are present for only 1 day in a week. For epidemiologic surveys, symptoms may be present for 3 weeks over a 3-month period (25% of the time).

The Rome II criteria for IBS have been modified from the Rome I criteria in several ways[3]: (1) They have been simplified by defining the specific symptoms regarding bowel habit (eg, > 3 bowel movements per week, straining at stool, hard stool) as only supportive rather than diagnostic of IBS; (2) Two of the 3 major criteria (rather than 1 of 3 for Rome I criteria) are now required for the diagnosis; and (3) Symptoms must be present for a longer time frame (12 weeks/year, rather than 3 weeks/3 months). These symptom item changes were based on new empiric evidence that helps to validate the criteria (primarily, factor analytic studies).

Subclassification of IBS

IBS can be stratified by subgroup based on predominant symptom or severity. These subclassifications can help the clinician to determine diagnostic (to exclude other diseases) and treatment approaches, and to stratify study populations for clinical trials.

Predominant symptom subclassification. IBS is often subclassified as diarrhea-predominant, constipation-predominant, or alternating (combination of both) at varying times. The Rome multinational working team proposed guidelines for predominant symptom subclassification based on stool frequency, stool form, and stool passage.[3] However, because IBS is characterized by dysregulation of bowel function, patients may often alternate between these subgroups, and thus their predominant symptom may change over time.[18,46] Moreover, a long-term study on the natural history of IBS and dyspepsia has shown that the predominant functional symptom can change over time not only within the specific diagnosis/disorder (eg, IBS), but also between different functional disorders (eg, IBS and dyspepsia).[17,18]

Symptom severity subclassification. Another strategy of subclassifying IBS patients is by the severity of the symptoms. Most subjects who have IBS symptoms do not see physicians for their symptoms (ie, IBS nonpatients). The majority (about 70%) of the subjects who do see physicians (ie, IBS patients) have mild and infrequent symptoms associated with little disability.[47] Twenty-five percent of IBS patients have moderate symptoms, which may occasionally interfere with daily activities (such as missing school, work, or social functions), and only a small proportion (about 5%) have severe symptoms that considerably affect daily activities and quality of life.

The severity of IBS symptoms is determined by their intensity, constancy, the degree of psychosocial difficulties, and the frequency of healthcare utilization.[11,31,47] Subclassifying IBS patients according to the severity of their symptoms can be helpful in guiding proper management. For example, patients with mild and infrequent symptoms can be managed by primary care physicians and usually require only reassurance, education, and dietary or lifestyle changes. Patients with moderate symptoms may require, in addition, pharmacologic and/or behavioral treatments. Patients who have severe, more frequent, or constant symptoms often require psychopharmacologic (eg, antidepressants) and/or psychological (eg, cognitive-behavioral) interventions and may need to be referred to tertiary centers.[11,12,47]

Diagnostic Testing

Once the diagnostic criteria have been met, it is necessary to exclude other medical disorders having similar clinical presentations. This is done by looking for alarm signs (see above) and by performing limited diagnostic screening tests. The diagnostic strategy should be planned in a cost-effective manner with consideration of the duration of the symptoms, age of onset of symptoms, family history of colon cancer, severity of the symptoms, previous diagnostic evaluations, psychosocial status, and change of symptoms over time.[3]

Detailed recommendations for diagnostic tests that can be used in this setting are found elsewhere.[3,11,12] In brief, the initial screening evaluation should include at least blood tests (eg, blood count, erythrocyte sedimentation rate, serum chemistries), stool tests (eg, for ova and parasites and blood), and sigmoidoscopy. Other studies such as colonoscopy, barium enema, ultrasound, or CT scan will depend on the presence of "alarm" signs as well as factors such as the patient's age and family history. More specific studies (eg, lactose breath hydrogen test, thyroid-stimulating hormone determination, celiac sprue serology) should be considered if indicated by features in the patient history or results of screening studies that point to other diagnoses.

If the initial screening evaluation is normal, further diagnostic studies should be withheld and treatment may be started with a follow-up visit within 4-6 weeks.[11] The patient should be reevaluated over time and additional diagnostic tests obtained depending on changes in clinical status and response to treatment. Nevertheless, it should be emphasized that the mere persistence of symptoms does not justify further diagnostic testing. Because IBS is a chronic disorder with frequent relapses, repeating diagnostic studies to "convince" the patient, or to rule out other disease entities, is not only unjustified but may be harmful in that it undermines the patient's confidence in both the diagnosis and the physician.[3]

Factors such as the severity of the symptoms, the patient's illness behavior (eg, recurrent complaints, recurrent physician visits and phone calls, requests for further testing), and even an incomplete response to symptomatic treatment must be considered in the management approach. However, these factors do not justify additional diagnostic testing in the absence of other "alarm" signs (eg, blood in the stool, abnormal physical examination, or laboratory studies). Rather, they may reflect the degree of psychosocial difficulties. As discussed earlier, psychosocial assessment is an essential part of the patient's evaluation and diagnostic planning. Clinicians should look for psychosocial factors that may exacerbate the clinical expression of the symptoms as well as the patient's illness behavior. Identifying or excluding these factors is helpful in establishing an appropriate diagnostic plan and in minimizing unneeded investigative studies.

Validity of the Diagnosis

How confident can a physician (and the patient) be with the diagnosis? In addition to the symptoms included in the major criteria, the Rome committee also listed symptoms that are not essential for the diagnosis but that are commonly present in patients with IBS (see Table). The presence of these symptoms can add to the physician's confidence regarding the origin of the symptoms (ie, GI) and the diagnosis (ie, IBS).[41] Nevertheless, development of symptom-based criteria in the absence of a diagnostic ("gold") standard has obvious limitations. The consensus achieved by expert clinicians and investigators can only provide face validity, and additional validation studies are needed to support the utility of the published criteria. Unfortunately, available data on the validity of the Rome criteria are still limited.

In a recent study, Vanner and colleagues[48] examined the predictive value of the Rome I criteria using the gastroenterologist's final diagnosis as the gold standard. The study authors found that the combination of the Rome criteria and the absence of "red flags" (weight loss, nocturnal symptoms, blood in stools, recent antibiotic use, family history of colon cancer, and abnormal physical examination) yielded 63% sensitivity and 100% specificity, with a positive predictive value (PPV) of 98% to 100% and negative predictive value of 76%. Additional studies on the validation of the Rome criteria, particularly the new (Rome II) criteria, are currently under way.

Additional support for a positive diagnosis of IBS also comes from studies that have looked at long-term outcomes. In long-term follow-up studies (up to 9 years from the diagnosis), no other explanation for the symptoms was found in 95% to 100% of patients.[49-51] This suggests that a positive diagnosis using symptom-based criteria, the absence of "red flags," and limited investigations rarely requires revision.

Conclusion

A positive and comprehensive diagnosis of IBS must incorporate both the recently developed symptom-based diagnostic criteria and the biopsychosocial approach. By identifying symptoms that are consistent with the disorder and that fulfill the Rome criteria, by excluding clinical alarm signs, and by performing limited diagnostic testing, the physician can achieve a positive diagnosis of IBS with a great deal of confidence.

The biopsychosocial approach offers a framework for incorporating the physiologic and psychosocial contributors to illness into the diagnostic plan. The patient's complaints, symptoms, and behaviors should be appraised in the context of the physiologic findings, the results of objective studies, the psychosocial factors surrounding the illness, and the patient's perception of his/her illness. This can lead to a more comprehensive understanding of the patient's illness and should improve management.

Table - Diagnostic Criteria* for IBS

Twelve weeks or more during the past 12 months with abdominal discomfort or pain that has 2 of the following 3 features:

  • Relieved with defecation

  • Onset associated with a change in frequency of stool

  • Onset associated with a change in form (appearance) of stool

The following symptoms are not essential for the diagnosis, but when/if present, increase confidence in the diagnosis and may be used to identify subgroups of IBS: Abnormal stool frequency (> 3 bowel movements (BM)/day or < 3 BM/week)

  • Abnormal stool form (lumpy/hard or loose/watery stool) > 1 out of 4 defecations

  • Abnormal stool passage (straining, urgency, or feeling of incomplete evacuation) in > 1 out of 4 defecations

  • Passage of mucus in > 1 out of 4 defecations

  • Bloating or feeling of abdominal distension > 1 out of 4 days


* In the absence of structural or metabolic abnormalities to explain the symptoms.
The 12 weeks need not be consecutive.

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