Causes of Chronic Diarrhea

Main Categories of Causes

The American Gastroenterological Association recommends considering various causes of chronic diarrhea, including colon diseases such as ulcerative colitis and Crohn's disease, which cause inflammatory diarrhea with bloody or mucoid stools 1, 2
The European Society of Gastrointestinal Endoscopy suggests that neoplasia and microscopic colitis are also important causes to be ruled out 1, 3
The National Institute of Diabetes and Digestive and Kidney Diseases states that small intestine diseases, such as celiac disease, can cause steatorrhea with pale, foul-smelling stools 1, 2
The American College of Gastroenterology recommends considering malabsorption of bile acids, which can cause diarrhea, especially in patients with diabetes and after ileal resection or cholecystectomy 1, 4

The Endocrine Society notes that hyperthyroidism can cause diarrhea through its effect on intestinal motility, accelerating intestinal transit time 1, 6
The American Diabetes Association states that diabetes mellitus can cause diarrhea through various mechanisms, including autonomic neuropathy, bacterial overgrowth, bile acid malabsorption, and medication effects (especially metformin) 1, 4, 6

The American Gastroenterological Association recommends reviewing medications, as up to 4% of chronic diarrhea cases are caused by medications, including products containing magnesium, antihypertensives, NSAIDs, theophylline, antibiotics, antiarrhythmics, and antineoplastic agents 1, 2, 4
The National Institute of Diabetes and Digestive and Kidney Diseases states that food additives, such as sorbitol and fructose, can cause diarrhea 1

The European Society of Gastrointestinal Endoscopy suggests that a thorough medical history and physical examination should be performed to identify "red flags" and guide further investigation 2, 3
The American College of Gastroenterology recommends initial laboratory tests, including complete blood count, electrolyte panel, and liver function tests, as well as thyroid-stimulating hormone (TSH) and glucose or HbA1c tests to screen for diabetes and thyroid disease 4, 5, 6
The National Institute of Diabetes and Digestive and Kidney Diseases states that further testing, such as SeHCAT scan or C4 level, may be necessary to confirm bile acid malabsorption or other conditions 4