gastrointestinal disorders
Irritable Bowel Syndrome (IBS)
Diagnosis of IBS
Clinical evaluation, based on Rome criteria Limited laboratory tests Other tests for patients with red flag findings Diagnosis of irritable bowel syndrome is based on history, specifically characteristic bowel patterns, time and character of pain, and absence of red flags, and a focused physical examination. Diagnostic testing should be more intensive when the following red flags are present either at initial presentation or at any time after diagnosis: Older age Weight loss Rectal bleeding Iron deficiency anemia Family history of colon cancer, inflammatory bowel disease, or celiac disease Nocturnal diarrhea Because patients with IBS can develop organic conditions, testing for other conditions should also be considered in patients who have red flags or develop markedly different symptoms during the course of IBS. Common illnesses that may be confused with IBS include Carbohydrate Intolerance None Diarrhea None Postcholecystectomy Syndrome None Laxative abuse Parasitic diseases (eg, Giardiasis ) Eosinophilic Gastritis or enteritis Microscopic colitis Small Intestinal Bacterial Overgrowth (SIBO) None Celiac Disease None Bile acid diarrhea Early Overview of Inflammatory Bowel Disease None However, uninflamed colonic diverticula do not cause symptoms, and their presence should not be considered explanatory. age 60 with acute symptoms, Ischemic Colitis should be considered. Patients with constipation and no anatomic lesions should be evaluated for Rare causes of diarrhea include Hyperthyroidism , Uninflamed colonic diverticula do not cause symptoms, and their presence should not be considered explanatory. Particular attention should be given to the character of the pain, bowel habits, familial interrelationships, and drug and dietary histories. Equally important are the patient’s overall emotional state, interpretation of personal problems, and quality of life. The quality of the patient–physician interaction is key to diagnostic and therapeutic efficacy. 2 of the following ( Diagnosis reference ): Pain is related to defecation. Pain is associated with a change in frequency of defecation. Pain is associated with a change in consistency of stool. Patients generally appear to be healthy. Palpation of the abdomen may reveal tenderness, particularly in the left lower quadrant, at times associated with a palpable, tender sigmoid. A digital rectal examination, including a test for occult blood, should be done on all patients. In women, a pelvic examination helps rule out ovarian tumors and cysts or endometriosis, which may mimic IBS. (See also the American College of Gastroenterology's2021 guidelines on the management of irritable bowel syndrome.) The diagnosis of IBS can reasonably be made using the Rome criteria as long as patients have no red flag findings, such as rectal bleeding, weight loss, or other findings that might suggest another etiology. Laboratory testing may include complete blood count and biochemical profile (including liver tests). For patients with diarrhea predominance, serologic markers for celiac disease (tissue-transglutaminase IgA with an IgA level) and testing for inflammatory bowel disease with fecal calprotectin or fecal lactoferrin and C-reactive protein are recommended ( Diagnosis reference ). For patients with constipation, measurement of thyroid-stimulating hormone and calcium levels is recommended. Testing for enteric pathogens, includingGiardia, is no longer recommended for patients with IBS unless there is a high pretest probability of infection. If there are definite risk factors forGiardiaexposure (eg, compromised water supply, travel, daycare setting, camping), fecal immunoassays or polymerase chain reaction testing forGiardiais recommended. Colonoscopy is recommended for patients>age 45 to exclude colonic polyps and tumors. The mucosal and vascular patterns in IBS usually appear normal. In patients with chronic diarrhea, particularly older women with more severe diarrhea, mucosal biopsy can rule out possible microscopic colitis. Additional studies (such as ultrasonography, CT, barium enema x-ray, upper gastrointestinal esophagogastroduodenoscopy, and small-bowel x-rays) should be undertaken only when there are other objective abnormalities. Fecal fat excretion or pancreatic elastase should be measured when there is a concern about steatorrhea. Small-bowel evaluation (eg, enteroscopy, capsule endoscopy) is recommended when malabsorption is suspected. Testing for carbohydrate intolerance or small intestinal bacterial overgrowth should be considered in appropriate circumstances. Patients with IBS may subsequently develop additional gastrointestinal disorders, and the clinician must not summarily dismiss their complaints. Changes in symptoms (eg, in the location, type, or intensity of pain; in bowel habits; in constipation and diarrhea) and new symptoms or complaints (eg, nocturnal diarrhea) may signal another disease process. Other symptoms that require investigation include fresh blood in the stool, weight loss, very severe abdominal pain or unusual abdominal distention, steatorrhea or noticeably foul-smelling stools, fever or chills, persistent vomiting, hematemesis, symptoms that wake the patient from sleep (eg, pain, the urge to defecate), and a steady progressive worsening of symptoms. Patients>age 45 are more likely than younger patients to develop an intercurrent physiologic illness. 1.Lacy BE, Pimentel M, Brenner DM, et al: ACG Clinical Guideline: Management of irritable bowel syndrome.Am J Gastroenterol116(1):17–44, 2021. doi: 10.14309/ajg.0000000000001036 