Hello, Chronic diarrhea causes are vary based upon the socioeconomic status of the population. In resource-rich settings, common causes are irritable bowel syndrome (IBS), inflammatory bowel disease, malabsorption syndromes (such as lactose intolerance and celiac disease), and chronic infections (particularly in patients who are immunocompromised). In resource-limited settings, chronic diarrhea is frequently caused by chronic bacterial, mycobacterial, and parasitic infections, although functional disorders, malabsorption and inflammatory bowel disease are also common. Your doctor need to evaluation for your alarm features include you age of onset after age 50 year, rectal bleeding or melena, nocturnal pain or diarrhea, progressive abdominal pain, unexplained weight loss, fever, or other systemic symptoms, laboratory abnormalities (iron deficiency anemia, elevated C-reactive protein), family history of inflammatory bowel disease (IBD) colorectal cancer. Characterizing the diarrhea type are very important to know. Some blood test and stool test need to do as well to find out the diagnosis. Imaging study should be done for you if the trial of treatment not improved. If the initial evaluation does not point toward a specific diagnosis, we perform additional testing. For patients with persistent diarrhea with no clear etiology after initial evaluation or diarrhea that does not respond to initial treatment, we perform additional testing to determine the underlying etiology. This evaluation is individualized based on the clinical presentation and can include screening for evidence of malabsorption, stool tests for evidence of an infection, and endoscopic evaluation but you already done endoscopic. We also perform imaging (abdominal computed tomography or magnetic resonance imaging) in patients with unexplained diarrhea and abdominal pain as a major symptom, systemic symptom (fever, weight loss), or suspected Crohn base on history. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr Heang Chan Raksmey, Family and General Physician