Irritable Bowel Syndrome

Diagnose IBS clinically when recurrent abdominal pain occurs at least 1 day per week and is associated with defecation and/or a change in stool frequency or form. Classify subtype with the Bristol Stool Form Scale: IBS-D has more than 25% of bowel movements with loose or watery stools, while IBS-C, IBS-M, and IBS-U require subtype assignment from the prevailing stool pattern. Use the same scale longitudinally to document treatment response or subtype shift. Wolters Kluwer+2Wolters KluwerDiagnosis and treatment of irritable bowel... : Journal of the American Association of Nurse PractitionersWolters KluwerDifferential Diagnosis of Chronic Diarrhea : Journal of Clinical GastroenterologyOxford AcademicIrritable bowel syndrome and diet | Gastroenterology Report

A symptom-based diagnosis is appropriate when the examination is unrevealing and alarm features are absent; in patients meeting Rome IV criteria for IBS-D without alarm features, symptom-based diagnosis has been reported as accurate in up to 98% of cases. Avoid broad food-allergy or food-sensitivity panels; reserve allergy evaluation for rapid, reproducible reactions that resolve with avoidance and are clinically compatible with food allergy. Wolters KluwerWolters KluwerDiagnosis and treatment of irritable bowel... : Journal of the American Association of Nurse Practitioners

At each initial or reassessment visit, ask specifically about rectal bleeding, unintentional weight loss, unexplained iron-deficiency anemia, nocturnal symptoms, new onset after age 45 to 50 years, acute unexplained symptom change, and a first-degree family history of colorectal cancer, inflammatory bowel disease, celiac disease, or significant gastrointestinal disease. These findings require evaluation for an organic disorder rather than labeling symptoms as uncomplicated IBS. Wolters Kluwer+2Wolters KluwerDiagnosis and treatment of irritable bowel... : Journal of the American Association of Nurse PractitionersWolters KluwerDifferential Diagnosis of Chronic Diarrhea : Journal of Clinical Gastroenterologycdn clinicaltrialsEvaluate and compare the clinical efficacy of the Mediterranean ...

For IBS-D or nonconstipated IBS without alarm features, obtain celiac serology with total serum IgA and tissue transglutaminase IgA. This combination identifies IgA deficiency that could make isolated tissue transglutaminase IgA testing unreliable and addresses celiac disease as a treatable mimic of chronic diarrhea and abdominal symptoms. Wolters KluwerWolters KluwerDifferential Diagnosis of Chronic Diarrhea : Journal of Clinical Gastroenterology

Use serum CRP together with fecal calprotectin or fecal lactoferrin when inflammatory bowel disease is a competing diagnosis in IBS-D. A fecal calprotectin value below 100 mcg/g, in a patient without alarm features and with normal routine blood testing, identified IBS with 98% certainty in one diagnostic investigation; an elevated marker should shift evaluation toward intestinal inflammation rather than functional treatment escalation. Wolters Kluwer+2Wolters KluwerDiagnosis and treatment of irritable bowel... : Journal of the American Association of Nurse PractitionersWileyDiagnosis and investigation of irritable bowel syndromeWolters KluwerDifferential Diagnosis of Chronic Diarrhea : Journal of Clinical Gastroenterology

Order a Giardia stool antigen only when exposure risk is present, including travel or immigration from endemic areas, untreated or inadequately treated water exposure, or daycare exposure. Do not use broad infectious testing as routine IBS workup in a stable, low-risk symptom pattern. Wolters KluwerWolters KluwerDifferential Diagnosis of Chronic Diarrhea : Journal of Clinical Gastroenterology

Explain that IBS is diagnosed positively and that treatment targets symptom control rather than a proven disease-modifying therapy. Establish the dominant target—abdominal pain, diarrhea, constipation, bloating, or urgency—and track it with weekly symptom frequency and Bristol stool form. Symptoms and predominant stool pattern can change over time, so reassess the treatment target rather than assuming initial subtype is fixed. BMJ+1BMJIrritable bowel syndromeWolters KluwerDiagnosis and treatment of irritable bowel... : Journal of the American Association of Nurse Practitioners

For global symptoms or constipation-associated symptoms, use soluble fiber such as ispaghula at 6 to 30 g/day. Soluble fiber has moderate-quality evidence in unselected IBS populations; its use is preferable to a nonspecific recommendation to increase dietary fiber without identifying fiber type. BMJBMJBest management of irritable bowel syndrome

For abdominal pain, consider an antispasmodic or enteric peppermint oil as first-line pharmacologic options. Examples reported include hyoscine 20 mg three times daily and peppermint oil 200 mg three times daily. Antispasmodics can cause dry mouth, dizziness, and blurred vision; choose them cautiously when anticholinergic adverse effects are likely to limit adherence. BMJ+1BMJBest management of irritable bowel syndromeBMJEffect of fibre, antispasmodics, and peppermint oil in the treatment of irritable bowel syndrome: systematic review and meta-analysis | The BMJ

For IBS-C, begin with laxative therapy for constipation. If constipation remains inadequately controlled after laxatives, offer a linaclotide trial; linaclotide is reported as a strong recommendation with high-quality evidence for IBS-C. Lubiprostone is also listed as a strongly recommended IBS-C option with moderate-quality evidence. BMJ+1BMJBest management of irritable bowel syndromeWolters KluwerS688 Irritable Bowel Syndrome Therapy and Cost in Uninsured : Official journal of the American College of Gastroenterology | ACG

For IBS-D, loperamide is a first-line option for diarrhea, although evidence for efficacy is limited. For persistent nonconstipated IBS symptoms, rifaximin is listed as a strongly recommended treatment with moderate-quality evidence; eluxadoline and alosetron are listed as conditional options. Treatment selection should follow exclusion of celiac disease, inflammatory bowel disease, and exposure-related Giardia when those diagnoses remain plausible. BMJ+2BMJBest management of irritable bowel syndromeWolters KluwerDifferential Diagnosis of Chronic Diarrhea : Journal of Clinical GastroenterologyWolters KluwerS688 Irritable Bowel Syndrome Therapy and Cost in Uninsured : Official journal of the American College of Gastroenterology | ACG

Alosetron and ramosetron are described as among the most effective options for diarrhea-predominant IBS in the cited management review, while the ACG-based summary characterizes alosetron as conditional with low-quality evidence. This difference supports reserving 5-HT3-directed therapy for selected refractory IBS-D after individualized risk-benefit assessment rather than positioning it as routine initial treatment. BMJ+1BMJBest management of irritable bowel syndromeWolters KluwerS688 Irritable Bowel Syndrome Therapy and Cost in Uninsured : Official journal of the American College of Gastroenterology | ACG

At follow-up, compare abdominal pain frequency, stool frequency, Bristol stool form, urgency, and functional impairment with baseline. Continue an intervention only when the measured target improves; when it does not, determine whether the failure reflects incorrect subtype targeting, inadequate adherence to a dietary or fiber trial, adverse effects, or an alternative diagnosis requiring renewed testing. BMJ+1BMJIrritable bowel syndromeWolters KluwerDiagnosis and treatment of irritable bowel... : Journal of the American Association of Nurse Practitioners

Escalate beyond routine IBS management when targeted testing is abnormal, an alarm feature emerges, or symptoms become newly atypical. A low fecal calprotectin result can support an IBS pathway in a low-risk presentation, but it does not supersede bleeding, anemia, weight loss, later-life onset, or a strong family history. Wolters Kluwer+2Wolters KluwerDiagnosis and treatment of irritable bowel... : Journal of the American Association of Nurse PractitionersWileyDiagnosis and investigation of irritable bowel syndromeWolters KluwerDifferential Diagnosis of Chronic Diarrhea : Journal of Clinical Gastroenterology

For persistent pain despite dietary, bowel-habit, and first-line analgesic approaches, use a neuromodulator pathway rather than repeatedly changing antidiarrheals or laxatives when pain is the main remaining symptom. For persistent IBS-C after laxatives, use linaclotide; for persistent IBS-D, consider rifaximin or a selected subtype-specific agent after revisiting celiac, inflammatory, and infectious alternatives. BMJ+2BMJBest management of irritable bowel syndromeWolters KluwerDifferential Diagnosis of Chronic Diarrhea : Journal of Clinical GastroenterologyWolters KluwerS688 Irritable Bowel Syndrome Therapy and Cost in Uninsured : Official journal of the American College of Gastroenterology | ACG