DIAGNOSIS Work-up Although the patient with IBS may present with mild nonspecific abdominal pain, the physical exam is typically normal.4,5 Patients who meet the Rome III diagnostic criteria—in the absence of alarm signs and symptoms or worrisome family history—are candidates for a clinical diagnosis of IBS.6 These criteria, originally developed for research purposes but useful in a clinical setting, include
• Symptom onset at least six months prior to diagnosis
• Recurrent abdominal pain or discomfort for more than three days per month during the past three months, and at least two of the following features:
• Improvement of symptoms with defecation
• A change in stool frequency
• A change in stool form.1,4,6
Due to inherent difficulty in establishing the accuracy of such criteria, a simple and practical alternative clinical definition is suggested by the American College of Gastroenterology Task Force on IBS: IBS is characterized by abdominal pain or discomfort that occurs in association with altered bowel habits over a period of at least three months.1 Patients meeting clinical criteria without alarm symptoms or worrisome family history require no additional testing.1
Moderate evidence supports routine testing for celiac disease in individuals presenting with symptoms consistent with IBS-D or IBS-M.1 Lactose hydrogen breath testing is recommended for individuals reporting symptoms that suggest a correlation between the ingestion of lactose and onset of IBS symptoms.1 When a patient presents with alarm features, significant family history, refractory symptoms, or new concerning symptoms, further testing is indicated, with test selection based on specific symptoms and risk factors.1,4,5
Differential Diagnosis In addition to IBS, there are numerous other conditions spanning several clinical categories that should be considered in patients who present with symptoms of IBS (see Table 1). In the cardiogenic group, abdominal angina, mesenteric artery thrombosis, and mesenteric artery venous thrombosis share common symptoms (eg, sudden stomach pain) with IBS, which may confuse the diagnostic picture. Gastrointestinal disorders such as bacterial overgrowth, celiac disease, gastroenteritis, inflammatory bowel disease, and anorectal dysfunction (incontinence) should be considered in patients who present with IBS symptoms. Pancreatic, ovarian, and colorectal cancer should also be investigated as a possible diagnosis.4,5,7
