For patients aged <50 years without alarm symptoms, diagnostic testing is unnecessary. Consider celiac sprue testing for patients with diarrhea (C).
Treatment is indicated when both the patient with irritable bowel syndrome and the physician agree that quality of life has been diminished (C). The goal of therapy is to alleviate global IBS symptoms (abdominal discomfort, bloating, and altered bowel habits that are life-impacting) (C).
Tegaserod, a 5HT4 receptor agonist, is more effective than placebo at relieving global IBS symptoms in women with constipation (A). Its effectiveness in men is unknown.
Alosetron, a 5HT3 receptor antagonist, is more effective than placebo at relieving global IBS symptoms in women with diarrhea (A).
Behavior therapy–relaxation therapy, hypnotherapy, or cognitive therapy–is more effective than placebo at relieving individual symptoms, but no data are available for quality-of-life improvement (B).
An extensive and expensive evaluation for irritable bowel syndrome (IBS) can be avoided if your patient is aged <50 years and is not experiencing alarm symptoms (hematochezia, 10 lbs weight loss, fever, anemia, nocturnal or severe diarrhea), has not recently taken antibiotics, and has no family history of colon cancer. An algorithm (Figure) indicates when work-up is needed and what it should entail.
Newer medications that act on 5HT receptors have proven effective in improving quality of life (global symptom reduction). Evidence supports the use of several traditional medications to reduce individual symptoms of IBS, but not for global symptom reduction.
FIGURE Evaluating possible irritable bowel syndrome
Who gets irritable bowel syndrome?
Ten percent to 15% of the North American population has IBS, and twice as many women as men have it.1 Symptoms usually begin before the age of 35 years, and many patients can trace their symptoms back to childhood.2 Onset in the elderly is rare.3 The disorder is responsible for approximately 50% of referrals to gastroenterologists.4
The company IBS keeps
Comorbid psychiatric illness is common with IBS, but few patients seek psychiatric care.5 Depression, anxiety, and somatoform disorders are seen in 94% of patients with IBS. IBS is common in patients with chronic fatigue syndrome (51%), fibromyalgia (49%), temporomandibular joint syndrome (64%), and chronic pelvic pain (50%).6 IBS often follows stressful life events,5,7,8 such as a death in the family or divorce. It tends to be chronic, intermittent, and relapsing.3
The symptoms of IBS can overlap with those of other illnesses, including thyroid dysfunction (diarrhea or constipation), functional dyspepsia (abdominal pain), Crohn’s disease or ulcerative colitis (diarrhea, abdominal pain), celiac sprue (diarrhea), polyps and cancers (constipation or abdominal pain), and infectious diarrhea.
Elusive physiologic mechanism
Several physiologic mechanisms have been proposed for IBS symptoms: altered gut reactivity in response to luminal stimuli, hypersensitive gut with enhanced pain response, and altered brain-gut biochemical axis.9 Though the symptoms of irritable bowel syndrome appear to have a physiologic basis, there are no structural or biochemical markers for the disease.
Use symptom-based criteria for diagnosis
Consider a diagnosis of IBS when a patient complains of abdominal discomfort and altered bowel habits. In the absence of a structural or biochemical marker, IBS must be diagnosed according to symptom-based criteria–such as Manning, Rome I, or Rome II–which have been developed for research and epidemiologic purposes. Though their clinical utility remains unproven, these criteria (delineated in Table 1) are the crux of clinical diagnosis for IBS.4,10-14 Subtypes of IBS have been described (diarrheapredominant IBS or constipation-predominant IBS), but they are not diagnostically useful, since the treatment goal is improved quality of life.
TABLE 1 Symptom-based criteria for irritable bowel syndrome
Abdominal discomfort or pain for at least 12 weeks (not necessarily consecutive) in the preceding 12 months, and having 2 of the 3 following features:
- relieved with defecation
- onset associated with a change in frequency of stool
- onset associated with a change in form (appearance) of stool
49%-65%*
100%*
69%-100%*
Supportive symptoms
Fewer than 3 bowel movements per week
More than 3 bowel movements per day
Hard or lumpy stools
*Found to have similar sensitivity and specificity to Rome I.14
Sn, sensitivity; Sp, specificity; PV+, positive predictive value
Dubious value of diagnostic tests
The literature regarding the value of diagnostic testing for IBS is controversial. Symptom-based criteria have varied in many studies, as have the criteria used to enroll patients and the measured outcomes of treatment (reduction in abdominal pain, in diarrhea, or in constipation, or improvement in quality of life). Because of these discrepancies, it is difficult to apply the literature clinically. Of the 6 landmark studies that considered the value of diagnostic testing for IBS patients,15-20 only 2 compared IBS patients with groups of healthy controls.17,19
