Chronic Idiopathic Diarrhea

Summary

Chronic diarrhea is defined as passage of loose stools for more than 4 weeks. In most instances the cause of chronic diarrhea can be discovered and treated effectively. A few less common causes also play a role: laxative abuse, small bowel bacterial overgrowth, and even bile acid malabsorption. Rarer syndromes account for a much smaller percentage of chronic diarrheas but may be more difficult to identify and treat. In a small number of patients, a cause for chronic diarrhea cannot be found and they are said to have chronic idiopathic secretory diarrhea, a fairly homogeneous disorder that can be sporadic or epidemic. This disorder can be diagnosed after excluding other causes of chronic diarrhea; it is associated with moderate weight loss and gradually subsides after 1.5–3 years. A sensible approach to the patient with chronic diarrhea of unexplained cause is based on a comprehensive history, focusing on the stool characteristics (watery, bloody, fatty), the occurrence of weight loss, aggravating and mitigating factors (with special emphasis on the diet); on a thorough physical examination and on the careful use of selected laboratory investigations such as complete blood count, comprehensive metabolic panel, thyroid tests, and of course stool tests such as bacterial cultures and extensive search for parasites; electrolytes, pH, occult blood test, leukocytes (or lactoferrin/calprotectin) and fat assessment. Subsequent analysis will depend on the findings from history, physical exam, and stool analysis and may or may not include more aggressive investigations such as CT enterography, small bowel follow-through radiograms, and videocapsule enteroscopy. Additional tests may have to be occasionally utilized, including plasma peptides (chromogranin, gastrin, calcitonin, VIP, somatostatin) and urine chemistry tests (5-HIAA, metanephrines, histamine).