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The evidence-based diagnosis of irritable bowel syndrome with constipation.

Usefulness of IBS definitions and classifications

Recognizing and accurately diagnosing an illness provides the foundation upon which a clinical care plan is based. In the case of irritable bowel syndrome (IBS), family practitioners are at the interface between patients and the healthcare system.

The vast majority of IBS patients (83%) in the US present in primary care (2) and accounted for approximately 3.1 million ambulatory care visits in 2004. (3) However, this is just the tip of the iceberg. It has been estimated that the majority of those who might experience IBS in the US remain undiagnosed, or 76.6% 2 of the total prevalence (typically thought to range from 10% to 15% but perhaps as high as 22%). (2,8-12) Equally frustrating is that more than half of those undiagnosed (53%) have reported that they had sought help in the past; of these, 1 in 4 may have been seen 5 times or more before receiving an accurate diagnosis. (2)

The past 20 years has seen an explosion in knowledge about the epidemiology, pathophysiology, diagnosis, and management of IBS. A number of expert working groups have endeavored to improve the recognition of IBS using symptom-based diagnostic criteria. The goal of these criteria has been to simplify and standardize the recognition of IBS for clinical researchers and healthcare providers alike. Some IBS diagnostic criteria that have been used include the Manning criteria, the Kruis criteria, and most recently, the Rome III criteria (2006). (14,64,65) The accuracy or predictive values for each of these criteria may not be ideal or have not yet been evaluated. Nonetheless, taken together, these efforts represent significant progress toward a more accurate characterization of IBS and its subgroups. A recent landmark contribution to the IBS literature is the 2009 "Evidence-Based Systematic Review on the Management of IBS" by the American College of Gastroenterology's (ACG) Task Force on IBS. (1) Released in January of 2009, this monograph reviewed the burgeoning data on IBS, some of which will be covered here as it applies to an evidence-based diagnosis for IBS-C.

Guidelines for IBS. The most common criteria used in research and clinical practice are the 2006 Rome III diagnostic criteria for IBS (an update of the Rome II criteria). (14) The Rome III criteria were developed by an international panel of experts in gastrointestinal disorders who defined IBS as "a functional bowel disorder in which abdominal pain or discomfort is associated with defecation or a change in bowel habit, and with features of disordered defecation." (14) In addition, the Rome III panel defined IBS as abdominal pain or discomfort recurring at least 3 days per month in the previous 3 months, and this pain or discomfort must be associated

with 2 or more of the following: (1) defecation improves pain or discomfort, (2) a change in stool frequency is associated with the pain or discomfort, and/or (3) a change in stool form/appearance is associated with the onset of pain or discomfort. Furthermore, these criteria must be met in the last 3 months of the onset of symptoms and at least 6 months prior to diagnosis. (14) Because the Rome III criteria represent the culmination of an exhaustive process that relied on the latest evidence and expert consensus, many have suggested that these criteria may be useful in clinical practice. On the contrary, others have argued that the complexity of the Rome III criteria make them best suited only for epidemiological research and clinical trials.

To achieve a more clinically useful and pragmatic definition of IBS, the recent ACG Task Force defined IBS as "abdominal pain or discomfort that occurs in association with altered bowel habits over a period of at least 3 months." (1)

Whether or not a family practitioner uses the Rome III or ACG definitions to identify IBS, the key characteristics of IBS are:

* Abdominal pain or discomfort

* Altered bowel function

* Recurrence of symptoms over an extended period

Gathering this information from the patient can be challenging because IBS symptoms are based on a patient's self-report. As discussed in the previous article in this supplement, clinicians should query patients about their IBS symptoms using simple, understandable terms. Clinicians also need to consider gender-related, cultural, and language barriers when seeking information on a topic that can be sensitive or embarrassing to many patients.

What is IBS-C? IBS-C is a subgroup classification of IBS, a clinically heterogeneous condition with an overall prevalence reported to range from 3% to 22%. (2,8-12) Although all IBS patients experience varying degrees of abdominal pain or discomfort, subgroups of patients will report a predominance of diarrhea or constipation while others will report a mixture of both. As such, the Rome III criteria provide a framework by which IBS patients can be characterized by 3 major subgroups: constipation-predominant, or IBS-C; diarrhea-predominant, or IBS-D; and mixed bowel pattern, or IBS-M. A small minority that do not fit these definitions are classified as unsubtyped (IBS-U) (TABLE). (14) Estimates of IBS subgroup prevalence vary substantially among studies, but most have reported a fairly even distribution among IBS-C, IBS-D, and IBSM. 1,13-15 Only a small proportion of patients fall into the IBS-U subgroup. 14 Subgrouping plays a critically important role in the choice of diagnostic tests and treatments in patients with IBS. The remainder of this review focuses on patients with IBS-C.

In clinical practice, subgrouping patients with IBS is best accomplished by focusing on stool consistency rather than stool frequency. Somewhat contrary to commonly held beliefs, stool frequency correlates poorly with patient reports of constipation; stool consistency correlates more reliably with patient complaints of constipation, as well as colon transit. As such, the Rome III criteria suggest subgrouping IBS patients based on differences in stool consistency. The Bristol Stool Form Scale (BSFS) provides a standardized, validated means by which to quantitate stool consistency (SEE FIGURE 2, PAGE S6). 54,66 Through the use of a pocket card or wall chart, the BSFS can easily be incorporated into a clinician's practice and greatly enhances the ability to accurately identify patients with IBS-C.

Clinical criteria for IBS-C. According to the Rome III criteria, patients with IBS-C have abdominal pain or discomfort, hard or lumpy stools at least 25% of the time, and loose or mushy stools less than 25% of the time (TABLE). (14,23,67)

IBS-C is a common and heterogeneous IBS subgroup, (68) and it is important to recognize that it can be clinically dynamic over time. Transitions between the subgroups have been reported, particularly between IBS-M and IBS-C. (69)

It is not entirely clear whether changes in symptoms represent the natural history of IBS-C or the consequences of treatment interventions. Regardless, symptom monitoring should occur during every patient visit to detect changes, which may range from subtle fluctuations that may not necessitate switching the subtype diagnosis, to significant differences. Bloating is an additional symptom commonly reported by IBS-C patients, (70,71) and in one study occurred more often in IBS-C patients (75%) compared to IBS-D patients (40.9%). (72) IBS-C patients have also been reported to experience more lower--and upper-abdominal pain compared to IBS-D patients, and significantly more overall GI symptoms (mean 6.67 [+ or -] 3.23) compared with those who have IBS-D (mean 4.62 [+ or -] 2.76; P<.001). (72)


What is the difference between IBS-C and chronic constipation? Abdominal pain or discomfort has been suggested to be the key discriminating characteristic between IBSC and chronic constipation. 14 The significant symptom overlap between IBS-C and chronic constipation can make distinguishing between the 2 conditions challenging. Shared characteristics of IBS-C and chronic constipation include less frequent stools, difficult defecation (straining), hard or lumpy stools, and the sensation of incomplete evacuation. Patients presenting with significant complaints of abdominal pain or discomfort as well as constipation are most accurately characterized as having IBS-C. On the other hand, patients reporting primarily constipation-associated symptoms and no or minimal abdominal pain or discomfort should be diagnosed with chronic constipation. Whether IBS-C and chronic constipation represent distinct disorders or the extremes of a continuum remains controversial, although emerging evidence suggests the latter. (73)

Comorbid illnesses

IBS patients typically experience decrements in health-related quality of life similar to those reported in other major illnesses, such as chronic kidney disease, hypertension, or diabetes. (16,17) Numerous other diagnoses and illnesses have been found to coexist with IBS, particularly gastrointestinal and psychiatric diagnoses, although unique relationships with IBS have not been established. (32,33) A few of the conditions commonly associated with IBS include gastroesophageal reflux disease (GERD), migraine, asthma, fibromyalgia, temporomandibular joint disorder, dysmenorrhea, and chronic fatigue syndrome. (17,33,74) It has also been recognized that patients with additional and overlapping disorders tend to have more severe IBS. (34)

GERD has repeatedly been shown to coexist with IBS by more than chance alone. (35-40) A 2007 study by Whitehead and colleagues found that 19% of IBS patients had GERD, a relationship that was more than 4 times as likely compared with controls (odds ratio [OR]: 4.26; confidence interval [CI], 3.49-5.20). (32) A 2008 study investigated this relationship in primary care and found a relative risk (RR) in GERD patients (n=6421) for incident IBS (n=2932) of 3.5 (CI, 2.3-5.4), and vice versa (RR, 2.8; CI,1.7-4.9). (40) Therefore, the risk is substantially elevated for either diagnosis. Predictors of the overlap of GERD and IBS are insomnia, frequent abdominal pain, higher rates of somatization, and higher body mass index. 40 Recent work also suggests that visceral hypersensitivity might provide a unifying hypothesis for the overlap of GERD and IBS symptoms. (75)

A wide range of psychiatric illnesses have been associated with IBS in primary care and the referral setting, including agoraphobia, anxiety disorder, depression, mood disorder, bipolar disorder, neuroticism, adverse life events, and somatization. (33,41-45) It is important to identify and address these issues because comorbid psychological distress probably influences clinical presentation (breadth and severity of symptoms) and response to treatment. (30)

Excess and often unnecessary surgeries have been found to be common in IBS patients. (46,47) Some surgeries were found to occur in IBS patients significantly more than in controls in a database of 89,000 patients with at least a 5% prevalence of IBS. Surgery types include cholecystectomy (OR, 2.09; 95% CI, 1.89-2.31), appendectomy (OR, 1.45; 95% CI, 1.33-1.56), and hysterectomy (OR, 1.70; 95% CI, 1.55-1.87). (46) Because of the inherent risks of surgery, Talley and colleagues have proposed that there may be previously undetected mortality in IBS patients who undergo surgery. (76)

Etiology and pathophysiology of IBS-C. The exact cause of IBS-C remains incompletely defined. Because IBS is a symptom-based diagnosis, it is unrealistic to expect that a single etiologic factor will be identified to explain the development of IBS-C in all patients. Rather, symptoms likely represent the summation of effects from a number of different factors that interact to varying degrees in a given patient. Potential contributing factors may include genetic predisposition, environmental stressors, behavioral factors, and the role of infection and inflammation contributing to decreased peristalsis. These factors may lead to some degree of disordered motility, (77) altered visceral sensitivity, (78,79) and/or central nervous system hypersensitivity. (80,81) An analogy would be that these factors are building blocks. In the case of IBS, different building blocks can result in the formation of the same symptom complex.

Which diagnostic tests are necessary in patients with IBS-C?

Absence of alarm features. In the absence of alarm features, few diagnostic tests are needed, with the exception of colorectal cancer screening for persons aged 50 and older. 1 Alarm features include rectal bleeding iron deficiency anemia, weight loss, and a family history of select organic diseases, including colorectal cancer, inflammatory bowel disease (IBD), and celiac disease. (82) Unfortunately, the ACG Task Force on IBS found that, in general, the presence of alarm features did not reliably identify patients with important organic diseases.' On the other hand, the absence of alarm features provides reassurance that the diagnosis of IBS is correct. (1)

Over-reliance on diagnostic tests. Related to patient expectations and perhaps influenced by medical-legal concerns, the commonly held view among clinicians is to approach IBS as a "diagnosis of exclusion," (48) ordering a wide variety of tests before assigning a diagnosis. It is not clear what drives patient expectations regarding diagnostic testing. It has been suggested that performing diagnostic tests may reassure patients that the diagnosis of IBS is correct. Recent work suggests that this may not be a valid rationale for ordering tests in IBS patients. 48 More likely, negative tests reassure the provider that the diagnosis of IBS is correct. In fact, recent evidence suggests that the majority of primary care clinicians view IBS as a diagnosis of exclusion rather than a diagnosis that can be confidently made using symptom-based criteria and excluding alarm features. (48) This has implications for the healthcare system and society at large. Compared with clinicians who do not believe IBS requires a differential diagnosis, clinicians who do believe this order 1.6 more tests, equivalent to $364 more per patient (P<.0001). Only 8% of IBS experts felt that IBS needed to be differentially excluded from other conditions, compared to 72% of community clinicians. (48)

The ACG Task Force on IBS advocated in its January 2009 evidence-based statement that clinicians who empirically treat and/or refer patients to a specialist when they are unsure of a diagnosis could reduce costs associated with unnecessary diagnostic tests. (1) A 2005 study by Spiegel and colleagues found a significant linear correlation between the number of diagnostic tests for IBS patients and the presence of somatization. (44) Healthcare costs might be substantially reduced if these patients were recognized and unnecessary additional diagnostic tests were avoided. (44) A simple, evidence-based diagnostic approach for IBS-C is shown in the FIGURE.

Standard blood tests and thyroid function testing. Based upon the available evidence, the ACG Task Force reported that complete blood counts and serum chemistries are not likely to detect other illnesses in IBS patients who have no alarm features compared to controls. (1,83) Further, the likelihood of identifying thyroid disease in patients with IBS symptoms and no alarm features is similar to that of the general population. Even when thyroid abnormalities are identified, they are rarely responsible for a patient's IBS symptoms. As a result, the ACG Task Force concluded that current evidence does not support routinely performing thyroid function tests in patients with IBS symptoms and no alarm features. (1) Of course, if there are other signs or symptoms of thyroid disease, it is entirely appropriate to pursue testing.

Lactulose and glucose breath testing. The relationship between IBS and small intestinal bacterial overgrowth (SIBO) remains quite controversial. One study found that IBS-C patients produced more methane than IBS-D patients (58% vs 28%, respectively), but IBS-C patients formed less hydrogen than IBS-D patients (42% vs 71%, respectively). (84) Although compelling and worthy of further investigation, translating such results to clinical practice remains problematic for a variety of reasons. First, the best test to identify SIBO in clinical practice remains unclear. Currently available tests include lactulose and glucose breath tests (85,86) and small bowel aspiration for quantitative culture. (87) Unfortunately, none of the available breath tests have been adequately standardized or validated as a test for SIBO. (88) Consequently, the ACG Task Force concluded that there is insufficient evidence to recommend routine breath testing in patients with IBS. (1)

Abdominal imaging. Only one study has tested abdominal ultrasound to detect abdominal or pelvic abnormalities in IBS patients. (89) Although gallstones were detected in 5% of patients, the validity of IBS diagnosis did not change or need to be revised, and therefore the ACG Task Force does not recommend the use of routine abdominal imaging in patients with IBS symptoms and no alarm features. (1)

Colonic imaging. Patients with IBS symptoms and no alarm features are no more likely to have colonic adenomas or colorectal cancer than persons from the general population. 1 As a consequence, the ACG IBS Task Force recommended that patients older than 50 years of age with IBS symptoms and no alarm features undergo colonic imaging for standard colorectal cancer screening. (1) Patients with IBS symptoms and alarm features, such as anemia or weight loss, should undergo colonic imaging to exclude organic disease. On the other hand, in patients younger than 50 years of age with IBS symptoms and no alarm features, colonoscopy is unlikely to uncover significant structural pathology or alter the diagnosis of IBS and, as such, is not routinely recommended. (1)

What does the future hold? For the foreseeable future, IBS and its subgroups will remain a symptom-based diagnosis where diagnostic tests are largely intended to exclude other organic diseases and, in that way, reassure the patient and physician that the diagnosis of IBS is correct. As understanding of the p athophysiology of IBS continues to improve, it is hoped that tests that rule out other diseases will be replaced by tests that rule in IBS. In a 2008 paper on the public health implications of the functional gastrointestinal disorders, Talley and colleagues commented, "... it seems likely that novel biological markers will eventually emerge if gut dysregulation is truly central to the pathogenesis." (76) In addition, recent research has begun to identify genetic polymorphisms that occur more commonly in patients with IBS. (90,91) The key to improved therapy is likely to emerge with better diagnostic tools. Treatment strategies are likely to become more individualized and more effective as progress is made to the point where diagnosis is predicated on symptoms and physiology rather than symptoms alone.

William D. Chey, MD, FACG


Department of

Internal Medicine


Gastrointestinal Physiology


Division of Gastroenterology

University of Michigan

Medical School


Michigan Bowel Control


Division of Gastroenterology

University of Michigan

Health System

Ann Arbor, Michigan
Rome III irritable bowel syndrome subgroup
schema by percentage of stool consistency (14)

                                               Loose (mushy)
                        Hard or lumpy          or watery
IBS subgroup            stools (%) (a,c)       stools (%) (b,c)

IBS with constipation   [greater than or       <25
  (IBS-C)                 equal to]25
IBS with diarrhea       <25                    [greater than or
  (IBS-D)                                        equal to]25
Mixed IBS-(IBS-M)       [greater than or       [greater than or
                          equal to]25            equal to]25
Unsubtyped IBS          Insufficient           Insufficient
                          abnormality of         abnormality of
                          stool consistency      stool consistency
                          to meet criteria       to meet criteria
                          for IBS-C, D, or M     for IBS-C, D, o rM

(a) Correlates to types 1-2 on the Bristol Stool Form Scale
(separate hard lumps like nuts [difficult to pass] or sausage
shaped but lumpy).

(b) Correlates to types 6-7 on the Bristol Stool Form Scale
(fluffy pieces with ragged edges, a mushy or watery stool,
no solid pieces, entirely liquid).

(c) When antidiarrheals or laxatives are not being used.
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Article Details
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Author:Chey, William D.
Publication:Journal of Family Practice
Article Type:Report
Geographic Code:1USA
Date:May 1, 2009
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