Treatment Guideline Chart
Irritable bowel syndrome is a common chronic gastrointestinal condition characterized by abdominal pain and bloating with altered bowel habits.
There are no identifiable physical, radiologic or lab abnormalities indicative of organic disease.
Symptoms may be exacerbated by stress, alcohol or food.

Irritable%20bowel%20syndrome Diagnosis


  • IBS patients do not have an increased risk of organic diseases compared to individuals without IBS, therefore the routine use of extensive diagnostic tests in IBS suspected patients is not necessary
  • Accurate history collection is needed for establishing the probability of a patient having an underlying organic cause of symptoms
  • Patients who present with any of the alarm signs and symptoms may have a higher incidence of organic disease and therefore routine diagnostic tests in these patients are considered appropriate


  • Careful history should include factors and medications that may mimic or exacerbate IBS symptoms
    • Eg Lactose, Sorbitol, magnesium-containing antacids that could cause diarrhea
    • Eg anticholinergics, calcium antagonists, diuretics, opioids that could cause constipation
  • Features in history that may be indicative of IBS:
    • Symptoms started >6 months ago
    • Aggravated by stress
    • Aggravated by meals
    • Frequent visits to the clinic due to abdominal problems without clear diagnosis
    • Symptoms worsen with anxiety/depression
    • With or without nausea, dyspepsia and/or heartburn

Physical Examination

  • Should reveal no evidence of organic disease that is responsible for patient’s symptoms

Abdominal Exam 

  • May reveal nonspecific tenderness in left lower abdomen over the sigmoid colon

Rectal Exam 

  • Should exclude anorectal abnormalities
  • In patients with abnormal rectal examinations suggesting dyssynergia or those with refractory constipation unresponsive to conventional therapy and with symptoms of a pelvic floor disorder, anorectal physiology testing may be considered to identify patients who could benefit from biofeedback therapy

Laboratory Tests

  • Routine evaluation should not include diagnostic tests as testing should be individualized (based on patient’s age, sex, family history of GI disease, predominating symptom, duration and severity of symptoms, presence of stress, other psychological factors, or non-IBS symptoms, availability and cost of test)     
  • Lab tests do not increase the diagnostic yield for IBS but if necessary, the following tests may be requested: 
    • Complete blood count (CBC)
    • Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), fecal calprotectin, fecal lactoferrin
      • Testing for inflammatory markers during 1st-line investigation avoids invasive procedures, eg colonoscopy or sigmoidoscopy, in excluding inflammatory causes of symptoms (eg IBD)
    • Stool exam (white blood cells, ova, parasites, occult blood)
    • Antibody testing [immunoglobulin A tissue transglutaminase (TTG), endomysial antibodies (EMA)] to rule out celiac disease
    • Thyroid function tests
    • Hydrogen breath test for lactose intolerance and small-intestinal bacterial overgrowth
    • Ferritin, folate and vitamin B12 levels


  • There are no structural, biochemical or physiological abnormalities that are demonstrated consistently in IBS patients
  • Diagnosis is thus symptom based and therefore, accurate history of patient’s symptoms is imperative
  • A positive diagnostic strategy is recommended compared to a diagnosis of exclusion in order to avoid unnecessary testing and reduce cost

Symptom-Based Criteria for Diagnosis of IBS (Rome IV Criteria)

  • Recurrent abdominal pain for at least 1 day/week in the past 3 months with ≥2 of the following:
    • Related to defecation
    • Associated with change in stool frequency
    • Associated with change in stool form (appearance)
  • Above criteria met for the past 3 months with symptoms starting at least 6 months prior to diagnosis

Symptoms cumulatively supporting the diagnosis of IBS 

  • Bloating
  • Abnormal stool frequency (>3x/day or <3x/week)
  • Abnormal stool form (hard/lumpy or mushy/watery)
  • Abnormal stool passage (straining, urgency or feeling of incomplete evacuation)
  • Passage of mucus

The Rome criteria are reliable only when there is no other metabolic or organic explanation that would account for patient’s symptoms 

Subclassification of IBS (Rome IV Criteria)

  • IBS with predominant diarrhea (IBS-D)
    • Mushy or watery stools >25% of bowel movements
    • Hard or lumpy stools <25% of bowel movements
  • IBS with predominant constipation (IBS-C)
    • Hard or lumpy stools >25% of bowel movements
    • Mushy or watery stools <25% of bowel movements
  • IBS with mixed bowel habits (IBS-M)
    • Both hard or lumpy and mushy or watery stools >25% of bowel movements
  • IBS unclassified (IBS-U)
    • Diagnostic criteria for IBS are met but bowel habits cannot be classified into 1 of the 3 groups above
    • May result from frequent changes in medications or diet or inability to discontinue medications affecting GI transit 
  • Patients commonly transition between subclasses at which diarrhea and constipation are commonly misinterpreted, thus subclass clarification should be routinely performed
    • Patients who complain of “diarrhea” may refer to the frequent passing of formed stools
    • In some patients, “constipation” may refer to complaints associated with attempts at defecation and not lesser frequency of bowel movements


Determine Severity of Symptoms

  • IBS symptoms can significantly diminish the quality of life of the patient
  • There is no data available to guide recommendations about the threshold to treat IBS
  • For some patients, it may be enough to be assured that their symptoms do not represent a life-threatening illness or cancer
  • Treatment should be offered to patients if it is felt that the symptoms are diminishing their quality of life
  • Below are general classification suggestions:


  • Infrequent symptoms
  • Little or no functional impairment or psychologic disturbance
  • Treatment should focus on establishment of physician-patient relationship, patient education, reassurance, dietary and medication modification and fiber supplementation


  • Disruptions of normal daily activities due to exacerbations of symptoms
  • May demonstrate psychologic distress
  • Symptom monitoring recommended to identify precipitating factors
  • Diet modifications, behavioral changes and psychotherapy may improve clinical picture
  • Pharmacologic intervention should be used to control symptom flares


  • Unrelenting pain often associated with underlying psychosocial difficulties
  • Treatment may involve behavioral modification, psychoactive drugs, and referral to a pain center

Specialist Referral

Diagnostic Tests 

  • Eg sigmoidoscopy, barium enema, colonoscopy, fecal occult blood tests, stool for ova and parasites, stool for culture
    • Though the diagnostic yield of colonoscopy is low among patients with IBS, it may be of value in ruling out organic diseases (eg IBD and malignancy) and microscopic colitis in patients presenting with alarm signs (eg recent change in bowel habits, unexplained weight loss, blood in the stool, anemia) 
  • Routine colon cancer screening is recommended for all patients ≥50 years 
    • >40 years in areas with high prevalence of gastric cancer
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