Diagnosing Irritable Bowel Syndrome: What's Too Much, What's Enough?

Abstract

What is the current approach to diagnosing IBS? Susan Lucak, MD, explores the issues.

Introduction

Irritable bowel syndrome (IBS) is the most common gastrointestinal disorder diagnosed in clinical practice in the United States. Because there is no biological marker to confirm the diagnosis of IBS, it is a diagnosis that has challenged clinicians for decades. In the past, IBS was a “waste-basket” diagnosis given to patients with unexplained gastrointestinal symptoms. It was considered to be “the diagnosis of exclusion” when extensive work-up for organic disease yielded no diagnosis.

In recent decades, it was recognized that patients with IBS experienced a constellation of specific gastrointestinal symptoms. Manning criteria were described in 1978,[1] followed by Rome I in 1989[2] and Rome II criteria in 1999.[3] Rome I and Rome II criteria were initially developed by multinational working groups to provide a framework for the selection of patients in diagnostic and therapeutic trials. These criteria are being continuously modified as we gain new knowledge about functional bowel disorders.

Recently published diagnostic guidelines[4,5] recommend using symptom-based criteria in making the diagnosis of IBS in clinical practice. Using these criteria in conjunction with “alarm features” allows a physician to minimize the extent of diagnostic testing needed to make the diagnosis of IBS. Furthermore, recent systematic review of the literature indicates that performing a number of diagnostic tests did not result in a significant increase in the diagnosis of organic gastrointestinal disease.[6]

This column discusses novel approaches to the diagnosis of IBS.

Epidemiology

When making the diagnosis of IBS, it is helpful to consider it in the context of its epidemiology. IBS is a very common gastrointestinal disorder in the United States, affecting 10% to 20% of the population.[7] Female patients outnumber male patients by 1.5–3.0:1.0 in most epidemiologic studies.[8] Although it is not well understood why more women present with IBS, differences in healthcare-seeking behavior may partly account for this predominance.

Smith and colleagues[9] found that psychosocial factors were determinants of healthcare seeking for patients with both organic gastrointestinal disorders and functional gastrointestinal disorders. History of abuse is another important determinant in healthcare seeking.[10]

Symptom-based Criteria

In a given patient, the diagnosis of IBS is suggested by identification of specific symptoms. The Rome II criteria for diagnosis of IBS include presence of abdominal pain or discomfort for 12 weeks (need not be consecutive) in the preceding 12 months, and at least 2 of the following 3 features regarding symptoms: (1) relieved with defecation, (2) associated with change in frequency of defecation, and /or (3) associated with a change in form or appearance of stool. Patients with IBS may have additional symptoms, including passage of mucus and bloating or abdominal distension (Table 1).[3] Although refinement and validation of these criteria are necessary, Rome II criteria are widely accepted as a diagnostic instrument in IBS.

Table 1.

Rome II Diagnostic Criteria for Irritable Bowel Syndrome[3]

Abdominal pain or discomfort for at least 12 weeks (need not be consecutive) in the preceding 12 months, accompanied by 2 of the following 3 features: Relieved with defecation Onset associated with a change in stool frequency Onset associated with a change in stool form (appearance)

Symptoms that are supportive of the diagnosis of IBS: Abnormal stool frequency, which may be defined as greater than 3 bowel movements per day or fewer than 3 bowel movements per week Abnormal stool form (lumpy/hard or loose/watery) Abnormal stool passage (straining, urgency, or feeling of incomplete evacuation); Passage of mucus Bloating or feeling of abdominal distension

“Alarm Features”

An important aspect of making the diagnosis of IBS is the absence of “red flag” or “alarm features” (Table 2).[4,11,12] Unexplained weight loss may reflect disorders such as malignancy, inflammatory bowel disease (IBD), or celiac disease. Persistent diarrhea or severe constipation may be associated with an organic disease.

Table 2.

“Alarm Features”[4,11,12]

History: Unexplained weight loss Persistent diarrhea Severe constipation Nocturnal symptoms Blood in stool New onset after age 50 years Family history of colorectal cancer, inflammatory bowel disease, or celiac disease Travel history to locations with endemic parasitic diseases

Physical examination: Fever Abdominal mass Fecal occult or overt blood on rectal examination Evidence of anemia Signs of bowel obstruction Signs of thyroid dysfunction Signs of malabsorption Active arthritis Dermatitis

Initial laboratory tests: Anemia Leukocytosis Elevated erythrocyte sedimentation rate (ESR) or C-reactive protein level Abnormal chemistries Abnormal thyroid-stimulating hormone (TSH)

IBS is generally an intermittent and recurrent disorder. Symptoms of IBS tend to disappear at night when the patient is asleep. Thus, nocturnal gastrointestinal symptoms warrant search for a diagnosis other than IBS. The onset of new gastrointestinal symptoms after the age of 50 should prompt the physician to look for organic disease, particularly colorectal cancer. Blood in stool may reflect IBD or an infectious process or colon cancer. Family history of IBD, celiac disease, or gastrointestinal malignancy requires evaluation for these diseases. Fever suggests the possibility of an infectious or inflammatory disorder. Anemia should alert the physician to look for IBD or colorectal cancer. Signs of bowel obstruction, malabsorption, extraintestinal signs of IBD, or thyroid dysfunction should all prompt organic disease work-up. Any laboratory test abnormalities should be pursued appropriately. Absence of these “alarm features” serves to support, not establish, the diagnosis of IBS.

Physical Examination

The American Gastroenterological Association (AGA) Technical Review on IBS recommends that a physical examination be performed, primarily to rule out organic disease.[4] For instance, the presence of abdominal mass, signs of obstruction, or enlarged liver should trigger further investigation. A rectal examination identifying lax sphincter may confirm complaints of fecal incontinence, whereas paradoxical pelvic floor muscle contraction may suggest pelvic floor dyssynergia. In the latter case, anorectal motility study may be appropriate. Digital rectal examination is of further value in the assessment for fecal occult blood. A pelvic examination (performed by a gastroenterologist or a gynecologist) should be performed if symptoms point to the pelvic/lower abdominal area and are associated with menses.

Diagnostic Testing

Review of the current literature does not support performance of extensive testing in patients who meet symptom-based criteria for IBS and who lack “alarm features.”[6,13] Cash and colleagues[6] performed a systematic literature review of frequently ordered diagnostic tests as part of IBS work-up (Table 3). After careful assessment of the quality and validity of the selected studies, it was concluded that the pretest probability of organic disorders (such as IBD, colon cancer, thyroid disease, and lactose malabsorption) was not significantly increased in patients suspected of having IBS when compared with the general population. In other words, when patients fulfilled symptom-based criteria for the diagnosis of IBS, performing tests such as flexible sigmoidoscopy, barium enema, colonoscopy, rectal biopsy, complete blood count (CBC), serum chemistries, fecal occult blood test (FOBT), TSH, stool ova and parasites (O&P), hydrogen breath test for lactose malabsorption, or abdominal ultrasound did not result in a significant increase in the diagnosis of organic gastrointestinal disease. Specifically, performing a colonoscopy did not result in identifying gastrointestinal organic disease in more than 1% to 2% of cases.

Table 3.

Prevalence of Organic Disease in Patients Meeting Symptom-Based Criteria for IBS[5,6]

Organic GI Disease	IBS Patients	General Population
Colitis/IBD	0.51% to 0.98%	0.3% to 1.2%
Colorectal cancer	0.00% to 0.51%	0.0% to 6.0% (varies with age)
Celiac disease	4.67%	0.25% to 0.50%
Gastrointestinal infection	0.0% to 1.5%	N/A
Thyroid dysfunction	6%	5% to 9%
Lactose malabsorption	22% to 26%	25%

Widespread testing for celiac disease in patients who fulfill symptom-based criteria for IBS is not recommended.[4,5] A matched case-control study in the United Kingdom showed 66 of 300 IBS patients had positive celiac disease auto-antibodies and 14 had biopsy-proven celiac disease compared with 2 out of 300 control subjects.[14] This demonstrates a 7-fold increase in occurrence of celiac disease in patients suspected of having IBS. This study was, however, conducted in a secondary care setting. Given availability of effective therapy for celiac disease and prevention of long-term morbidity, testing for celiac disease with celiac disease auto-antibodies may not be unreasonable.

The most recent AGA Technical Review on IBS[4] recommends the performance of screening and other diagnostic tests as listed in Table 4. Colonic visualization with colonoscopy or flexible sigmoidoscopy/barium enema should be performed according to colorectal cancer screening guidelines. A colonoscopy is recommended for patients over the age of 50 years, but in younger patients, performing flexible sigmoidoscopy or colonoscopy needs to be determined by clinical presentation and sound clinical judgment.[4,5] In many cases, therapy can be instituted before diagnostic studies are done or completed.

Table 4.

Screening and Other Tests Recommended in Patients With Suspected IBS[4]

CBC FOBT ESR* Serum chemistries* TSH* Stool O&P*

*To be ordered depending upon symptom pattern

ESR, erythrocyte sedimentation rate; FOBT, fecal occult blood test; O&P, ova and parasites

The American College of Gastroenterology (ACG) Task Force comments on the value of “reassurance” derived from negative evaluation for organic disease.[5] It is pointed out that the value of this “reassurance” is unclear and should be assessed in future clinical trials.

The extent to which a diagnostic work-up is performed also depends on the severity of symptoms and where a patient with IBS presents.

Primary Care Setting

Most patients with IBS (about 70%) present to primary care physicians.[4] Patients with IBS in this group have symptoms that tend to be mild in severity. A recently published evidence-based review by the ACG IBS Task Force concluded that routine testing among patients with symptoms “fitting” the Rome II criteria and no “alarm features” is not necessary in the primary care setting.[5]

Secondary Care Setting

More difficult or more severe cases of IBS are generally seen by gastroenterologists referred from primary care physicians. The estimated prevalence of this subgroup is about 25% of all patients with IBS.

If screening and other diagnostic tests were done by the primary care physician, they do not need to be repeated. The need for colonic visualization should be determined according to guidelines outlined above. Further evaluation may be warranted if a patient presents with any of the following features: (1) short duration of symptoms or worsening severity of symptoms, (2) onset of symptoms at an older age (> 50 years), (3) family history of colon cancer or IBD, or (4) absence of psychosocial features or absence of healthcare seeking.[4]

During the first visit, it is important to explore with the patient possible contributing factors such as psychosocial issues (stress, anxiety, depression) and history of abuse. Up to 40% of patients may have a history of sexual, physical, or mental abuse.[10]

Clearly, the right balance needs to be struck between making an accurate diagnosis of IBS and, at the same time, not missing other diagnoses that may mimic IBS. It is important to recognize, however, that if a patient diagnosed with IBS does not respond to a therapy, the diagnosis may be reassessed in 3 to 6 weeks and additional evaluation can be performed (see Table 5).[4]

Table 5.

Diagnostic Evaluation Based on Symptom Subtype After Initial Treatments Are Insufficient to Control Patient's Symptoms[4]

Predominant Symptom	Diagnostic Tests
Constipation:
Infrequent bowel movements Obstructed defecation	Whole-gut transit test Anorectal motility plus balloon expulsion Defecating proctography Rectoanal angle measurement
Diarrhea:	24-hour stool volume and fat study
	Stool osmolality, electrolytes, and laxatives
	Transit test: small bowel and colon
	Cholestyramine trial
	Jejunal biopsy/aspirate (O&P, bacterial overgrowth)
	Colonic biopsies
	Other carbohydrate-hydrogen breath test (eg, fructose, sorbitol)
	? Rectal sensation test
Pain:	Plain abdominal x-ray
	Small bowel follow-through examination
	CT/MR imaging
	Pelvic ultrasound
	? Gastrointestinal manometry
	? Balloon distention test

Tertiary Care Setting

The most severe cases of IBS and those most difficult to treat are seen in referral centers. The latter group comprises approximately 5% of all IBS cases. The clinical symptoms for this patient group do not tend to correlate with gut physiology. Rather, these patients tend to have constant symptoms, more psychosocial difficulties, greater healthcare-seeking behavior, more illness behavior (illness behavior is a way in which an individual perceives, interprets, and reacts to physical sensations that can be interpreted as symptoms of disease), and more psychiatric diagnoses.[4]

Generally, most diagnostic studies have been performed by the time a patient with IBS presents to a referral center. Specialized studies such as defecating proctography, rectoanal angle measurement, anorectal motility and balloon expulsion, and investigational testing may be performed depending on clinical presentation and lack of response to previous treatments (see Table 5).[4]

Differential Diagnosis and Durability of Diagnosis

Differential Diagnosis

Symptoms of IBS are nonspecific and may mimic a number of disease entities (Table 6).[15] It is important to recognize that in a given patient with IBS, these diagnoses need not be “excluded” before a diagnosis of IBS can be established.

Table 6.

Differential Diagnosis of IBS[15]

IBS with diarrhea Dietary - lactose, sorbitol, fructose, caffeine, alcohol, fatty foods, fat substitutes, gas-producing foods Infections — Giardia spp, Amoeba spp, HIV-related, bacterial overgrowth IBD — Crohn's disease, ulcerative colitis, microscopic colitis Drug toxicity — antibiotics, proton pump inhibitors, nonsteroidal anti-inflammatory drugs, ACE inhibitors, beta-blockers, chemotherapy Malabsorption — celiac disease, bile acid-related Other — ovarian cancer, endometriosis, colorectal cancer, hyperthyroidism, carcinoid, VIPoma, ischemic colitis

IBS with constipation Dietary/mode of life — inadequate fiber, immobility Neurologic — Parkinson's disease, multiple sclerosis, spinal cord injuries Endocrine — diabetes, hypothyroidism, hypercalcemia Drug toxicity — opiate analgesics, calcium-channel blockers, antidepressants, clonidine Other — colorectal cancer, ovarian cancer, bowel obstruction, diverticular disease, endometriosis

Durability of Diagnosis

A number of studies conducted in community-based and specialty-based clinics over the past 3 decades have demonstrated that once the diagnosis of IBS is made, only a small percentage (0.7% to 6.5%) of patients subsequently receive a diagnosis of organic disease.[16-20] These studies provide evidence that once the diagnosis of IBS is established, additional studies are not necessary unless the clinical symptoms change.

Legal Risks in Diagnosing IBS

Some physicians who see patients with IBS are concerned about the risk of malpractice. Feld[21] recently described sources of risk under which physicians may be sued, including negligence, duty to provide care to a patient, and medical practice below standard of care, among others. But the idea that more testing is better in IBS may not always be the case. For example, colonoscopy leads to a change in diagnosis about 1% to 2% of the time and may represent performance of substandard care based on testing guidelines for IBS diagnosis recommended by gastroenterological associations in the United States. Therefore, any complication resulting from “unnecessary” testing may expose a physician to a malpractice suit. Alternatively, if a physician explains to a patient why only limited testing is necessary, this allows a patient to participate in the process and understand inherent uncertainties and thus share in the responsibility when a reasonable decision results in an adverse outcome.[21] Feld's risk management recommendations are outlined in Table 7.

Table 7.

Risk Management Recommendations for the Physician Treating IBS[21]

Know the IBS guidelines; keep current with literature and national society recommendations Practice within the standard of care as follows: Application of symptom-based criteria (preferable), although clinical diagnosis may be sufficient Use red flags/alarm symptoms Limited work-up, directed by red flags Use of clinical judgment to modify the above (consider additional evaluation if there is physician or patient concern or if patient's symptoms persist) Use an informed consent approach; this involves: Communication Patient education Shared decision making, which helps transfer the risk of an adverse event Document discussions, including those involving informed consent and, perhaps, the possibility of missed diagnosis Accept realistic goals Keep adequate malpractice insurance Certain legal elements must be met for a malpractice suit to be successful

Summary and Conclusions

What's too much when we think about diagnosing IBS is to do exhaustive and duplicate testing. In a retrospective, community-based study in Olmsted County, Minnesota, two thirds of patients who consulted for gastrointestinal symptoms had to wait at least 2 years to have their IBS diagnosed, despite averaging nearly 5 healthcare visits per year.[20] Such an approach is not only costly and inefficient, but it delays treatment and fosters frustration on the part of the patient and the physician.

What's enough is to use symptom-based criteria, “alarm features,” and guidelines proposed by the ACG IBS Task Force and the AGA Technical Review on IBS in making a more timely diagnosis of IBS. Although additional studies are necessary to validate Rome II criteria and to assess diagnostic testing in prospective studies, the expert guidelines allow the diagnosis of IBS to be made with greater efficiency, certainty, and confidence. Furthermore, once a diagnosis of IBS is made, it is retained in more than 93% of cases with a long-term follow-up. Considering legal aspects of IBS diagnosis, symptom-based criteria and guidelines set forth by the ACG and AGA are becoming key elements in establishing standard of care. It has become clear that the diagnosis of IBS can and should be made quickly so that treatment can be initiated as soon as possible. This promotes greater patient confidence in the physician.

IBD, inflammatory bowel disease; GI, gastrointestinal; N/A, not available

CT, computerized tomography; MR, magnetic resonance; ?, consider performing

ACE, angiotensin-converting enzyme; HIV, human immunodeficiency virus; IBD, inflammatory bowel disease; VIPoma, vasoactive intestinal polypeptide