A patient reports recurrent abdominal cramping, bloating, and alternating diarrhea and constipation for 8 months; stool studies are normal and colonoscopy 2 years ago was unremarkable. Which analytic conclusion best supports an IBS diagnosis and which feature argues against it?

• A. Conclusion supporting IBS: chronic functional symptoms with normal labs and prior negative colonoscopy; Feature arguing against IBS: presence of persistent unexplained rectal bleeding, which would prompt evaluation for organic disease.
• B. Conclusion supporting IBS: positive stool cultures indicating infectious cause; Feature arguing against IBS: symptom fluctuation with stress or certain foods, because IBS by definition has no relation to psychosocial triggers.
• C. Conclusion supporting IBS: progressive weight loss and iron-deficiency anemia; Feature arguing against IBS: symptoms relieved by bowel movements, which is inconsistent with IBS diagnostic criteria.
• D. Conclusion supporting IBS: abrupt onset of nocturnal diarrhea and fever; Feature arguing against IBS: normal colonoscopy as IBS always shows gross mucosal changes detectable by endoscopy.

Answer: (A)