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Making a Positive Diagnosis of Irritable Bowel Syndrome

Dan L. Dumitrascu, MD

Abstract: The traditional diagnostic approach for irritable bowelsyndrome (IBS) is to exclude other gastrointestinal conditions,which has led to patients being subjected to excessive testing.However, the development of consensus guidelines, such as RomeIII, has enabled physicians to make a positive diagnosis of IBSbased on the pattern and nature of symptoms. It is now possible toemploy a more rational diagnostic strategy with a reduced need forlaboratory testing based on symptom-based approaches aimed atstandardizing IBS patient subgroups. Patient outcomes in IBS canbe further improved by careful consideration of several diagnostic

issues including differentiating between disorders (IBS is 1 of >20functional gastrointestinal disorders), practical aspects of testing,the indications for colonoscopy, and the need to improve thephysician-patient relationship and enhance the patients adherenceto treatment.

Key Words: diagnosis, irritable bowel syndrome, symptoms

(J Clin Gastroenterol 2011;45:S82S85)

Making a positive diagnosis of irritable bowel syndrome(IBS) is of great importance to provide the optimaltherapeutic approach for each individual patient. Thisprocess is, however, complicated by the fact that the

presence of IBS, which is defined as a functional gastro-intestinal disorder (FGID), is not associated with anydefinitive biochemical, serologic, or structural/organicabnormalities.1 The majority of patients with IBS seekmedical care because of abdominal pain or discomfortassociated with altered bowel habits, and these areconsidered to be the hallmark features of IBS. As thesesymptoms are common to a number of other gastrointest-inal conditions, IBS was long considered a diagnosis ofexclusion with patients suffering the characteristic symp-toms consequently subjected to excessive testing. Thedevelopment of symptom-based approaches aimed atstandardizing IBS patient subgroups combined with thedevelopment of consensus guidelines advocating a positive

diagnosis of IBS, based primarily on the pattern and natureof symptoms, have led to a more rational diagnosticstrategy without the need for excessive laboratory testing.2,3

This study considers the issues surrounding thediagnosis of IBS in clinical practice, including differentialdiagnosis, practical aspects (such as which, how, and when

to perform tests), the specific indications for colonoscopy,and suggestions for improving the physician-patient re-lationship with a view of optimizing patient outcomes.

DIAGNOSING IBS

The purpose of diagnosis is to define the presence andspecific characteristics of IBS, to understand the magnitudeof the problem for the patient and also in terms of

prognosis, and to understand pathogenic factors in eachcase. To achieve these ends, it is important to interact wellwith the patient so that we can establish all relevant facts.

Several attempts have been made to produce guide-lines, which allow a physician to make a positive diagnosisof IBS from the presenting symptoms (rather thanexcluding underlying organic disease using extensive tests).This process started in 1978 with the publication of theManning criteria and has been transformed by the ongoingRome process,38 culminating in Rome III (2006), thepresent diagnostic criteria.9,10 An attempt to use adiagnostic score including organic findings with negativepredictive value (Kruis criteria)11 was not adopted, how-ever, because it was considered too complicated to use.

IBS is 1 of >20 FGIDs. As defined by the RomeMultinational Working Teams, the FGIDs vary in theirclinical features, but are characterized by chronic or recurrentsymptoms attributed to the gastrointestinal tract. They mayexist from pharynx and esophagus to anorectum. Thesedisorders may relate to abnormalities in motility or afferentsensitivity as modulated by the central nervous system.8,12

The functional bowel disorders (FBD) include: (a)IBS, the most common and most extensively studiedfunctional disorder; (b) functional abdominal bloatingreferring to abdominal fullness, bloating, or distensionunrelated to obvious maldigestion (eg, lactose intolerance)or excess consumption of poorly digestible but fermentablefood stuffs (eg, sorbitol, beans, wheat bran), in the absence

of functional dyspepsia or IBS; (c) functional constipation,defined as straining at defecation, a sensation of incompleteevacuation, and the infrequent (2 or fewer) passage oflumpy or hard stools in the absence of IBS; and (d)functional diarrhea; referring to the frequent (>3/d) andpainless passage of unformed stools associated with a slightincrease in stool volume (

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discomfort or pain is associated with defecation or a change

in bowel habit, and with features of disordereddefecation.8 This differs from the Rome I definition byintroducing the concept that IBS is not likely to be onedisease. Rather it is a general description of a group ofsymptoms that may subsume several more specific sub-group conditions. Examples might include patients withpostinfectious IBS (PI-IBS), or impaired central regulationof pain associated with psychosocial difficulties.13 Rome IIIdefines IBS as a FBD in which abdominal pain ordiscomfort is associated with defecation or a change inbowel habit, and with features of disordered defecation.9,10

Specifically, the Rome III diagnostic criteria (ie, fulfilled forthe past 3 months with symptom onset at least 6 mo beforediagnosis) are met when recurrent abdominal pain or

discomfort for at least 3 days a month in the past 3 monthsis associated with 2 or more of the following:10

Improvement with defecation Onset associated with a change in frequency of stool Onset associated with a change in form (appearance)

of stoolDiscomfort refers to an uncomfortable sensation, not

described as pain; in pathophysiology research and clinicaltrials, a pain/discomfort frequency of at least 2 days a weekduring screening evaluation is recommended for patienteligibility.10

Other changes in Rome III included the use of stoolconsistency scale to identify IBS subtypes (bearing in mindthat subtyping of IBS is controversial). This can be aided by

use of the Bristol Stool Form Scale. A new category wasintroduced, PI-IBS, and 2 pediatric categories (ie, neonate/toddler and child/adolescent) were suggested instead of 1used previously.15

Overall, diagnostic testing should be guided by thepatients age, primary symptom characteristics, and otherclinical and laboratory features. Rome III also recommendsthat treatment of FBDs be based on an individualizedevaluation, explanation, and reassurance. Alterations indiet, drug treatment aimed at predominant symptoms, andpsychotherapy may be beneficial.

DIFFERENTIAL DIAGNOSIS

Once the diagnostic criteria for IBS have been met, it is

necessary to exclude other medical disorders having similarclinical presentations. This is done by looking for alarmsigns (by taking a thorough patient history along with

abdominal and extra-abdominal examinations) and byperforming limited diagnostic screening tests.13

Appropriate laboratory tests include complete bloodcount, lactulose breath H2 (to diagnose small intestinalbacterial overgrowth), endomysial components of antibo-dies to tissue transglutaminase, 23-Seleno-25-homo-tauro-

cholate scan, amongst many other appropriate tests. Stooltests include analyses for occult blood, leukocytes, calpro-tectin, bacteria, and parasites.

An important consideration is whether or not toperform endoscopy, one issue being that the same symptomsmay show different endoscopic patterns. Colonoscopy iscertainly indicated in patients aged Z50 years and otheroptions include the use of sigmoidoscopy, virtual colono-scopy, and videocapsule.

Among patients meeting symptom-based criteria forIBS, the pretest probability of inflammatory bowel disease,colorectal cancer, or infectious diarrhea is 1% and isthe dominant strategy when the prevalence exceeds 8%.17

The diagnosis of inflammation in IBS is not yetconsidered routine and is presently best reserved forresearch purposes. Indeed, the latest edition of Surgical

Pathology of the GI Tract, Liver, Biliary Tract andPancreas: advises that: Perhaps the most important aspectof evaluating colorectal biopsy specimens is having a keensense of the normal colon. Often, it is difficult to decidewhether a biopsy specimen is at the upper limit of normalor the lower limit of abnormal, and in many respects, this isa subjective evaluation.18

Similarly, motility studies in IBS and tests for visceralhypersensitivity are useful for research but are presently notwarranted in routine practice. Motility tests include pro-longed increase in 3-cycles/min colonic motor activity after ameal; an exaggerated increase in 3-cycles/min motor activityin response to stressors and cholecystokinin; and increasedvisceral sensitivity and motor activity in response to balloon

distention. Barostats, frequently used in neurogastroentero-logy research, are used for measuring gut wall tension orsensory thresholds in the gut. They can be used to diagnosevisceral hypersensitivity that may arise after repetitive bowelstimulation, acute inflammation, or neurological trauma (eg,surgical operations and other invasive procedures). Interest-ingly, patients with IBS show altered brain responses to rectalstimuli consistent with reported alterations in autonomic andperceptual responses to visceral stimuli and may be related toaltered central noradrenergic modulation.19 The presence ofvisceral hypersensitivity may suggest allodynia or sensitiza-tion, and therefore the role of trauma, patient personality,and infection should be investigated.

If PI-IBS is suspected (and approximately a third of

patients with IBS have previously suffered from acutegastroenterocolitis10,2025), then it is likely that inflamma-tion is a trigger for visceral hypersensitivity and gut motility.

TABLE 1. Pretest Probability of Organic Disease in PatientsFulfilling IBS Criteria

Organic Disease

IBS Pretest

Probability

General Population

Prevalence

Colitis/IBD 0.51-0.98 0.3-1.2

Colon cancer 0-0.51 4-6Celiac disease 4.67 0.25-0.5GI infection 1-1.7 N/AThyroid

dysfunction6 5-9

Lactosemalabsorption

22-26 25

GI indicates gastrointestinal; IBD, inflammatory bowel disease; IBS,irritable bowel syndrome.

Adapted with permission from Cash et al, Am J Gastroenterol.2002;97:28122819.

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Routine diagnosis of PI-IBS should, therefore, take intoaccount the possible presence of inflammatory cells in rectalbiopsies and the expression of inflammatory mediators.

Although the genetic diagnosis of IBS is certainly onefor the future, progress has been made in the identificationof predisposing factors.2633 For example, various motilityand inflammation-sensitization polymorphisms have nowbeen identified, including: cytokines (eg, IL-10), serotonin-transporter-linked promoter region (5HTT-LPR), the a2-

adrenergic receptor, and the G-protein (C825T) b3 subunit.Measurable and potentially useful alterations in centralnervous system regulatory pathways include hypothalamic-pituitary-adrenal reactivity and affective/pain modula-tion.34 Other genetic avenues to explore include the linkageof IBS to psychiatric comorbidity including depression andpanic disorder, and also posttraumatic stress disorder.

Generally speaking, psychological or psychiatric assess-ment in IBS should be reserved for severe cases. Bear in mindthat a psychiatrist might consider a somatoform disorder,such as IBS, to be a mental disorder characterized by physicalsymptoms that mimic physical disease or injury and forwhich there is no identifiable physical cause. A pathologicalcondition can be considered to have 3 aspectsthe disease

itself (organ and/or functional impairment), the illness (thepatients subjective impairment), and the sickness (ie, socialrole or impairment). Reflecting this, a biopsychosocial modelcan been proposed that integrates the various psychologicaland physiological factors into a conceptual framework thathelps explain the clinical symptoms, illness behavior, andtreatment outcomes (Fig. 1).1,9

IMPROVING THE DOCTOR-PATIENT

RELATIONSHIP

One of the clinicians most difficult tasks is to success-fully care for patients with painful and refractory FGIDs. It isimportant to appreciate the many concerns patients may have

when they seek medical care.35 They are likely to suffer painbut may know nothing about IBS. Can it be cured? Will it bepossible to lead a normal life? They could also be very worried

about the possibility of colorectal cancer. The physician mayalso have a range of concerns when approaching thediagnosis. Is this a serious condition? What are the recentrelevant events in the patients life? Should I refer the patientfor further tests? Could the patient be taking narcotics orlaxatives? Is there a psychological involvement? Furthermore,in the course of evaluating and caring for patients, difficultiesmay result from misunderstandings between patient andphysician or from comments that reflect unstated issues. In

both cases, mutual dissatisfaction ensues when these under-lying factors are not properly addressed. However, it isimportant for the physician to develop a communication stylethat supports an effective patient-physician interaction, toimprove the therapeutic outcome.3638 This can be achievedthrough empathy, reassurance, education, and a negotiatedand realistic treatment plan. It is also of value to ask severalquestions during the first visit to assess the psychosocialcontributions to the illness, and to provide the option forpsychological consultation and treatment as a way to help thepatient better control the symptoms.

In summary, although the diagnosis of IBS might seemto be straightforward it is important to acknowledge that it isnot. Once the diagnostic criteria for IBS have been met

(based on Rome III), it is necessary to exclude other medicaldisorders having similar clinical presentations. The diagnosticstrategy should be planned in a cost-effective manner withconsideration of the duration of the symptoms, age of onsetof symptoms, severity of the symptoms, previous diagnosticevaluations, psychosocial status of the patient, family historyof colon cancer, and change of symptoms over time. Finally,an approach that encourages a good interaction with thepatient is likely to improve patient and physician satisfaction,adherence to treatment, and clinical outcome.

REFERENCES

1. Longstreth GF, Thompson WG, Chey WD, et al. Rome III: thefunctional gastrointestinal disorders. 3rd ed. McLean, Virginia:Degnon Associates; 2006:490509.

Physiology

Motility

Sensation

Inflammation Altered bacterial flora

Brain

CNS

Gut

ENS

Psychosocial

factors

Life stress Psychological state Coping Social support

Outcome

Medications

MD visits

Daily function

Quality of life

FGID

Symptoms

Behavior

Early life

Genetics

Environment

FIGURE 1. Biopsychosocial conceptual model in FGID (based on information provided by the Rome III criteria). 1,9 CNS indicates centralnervous system; ENS, enteric nervous system; FGID, functional gastrointestinal disorder.

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