Definition and Diagnosis of Chronic Diarrhea

Diagnostic Criteria

The American Gastroenterological Association defines chronic diarrhea as the abnormal passage of three or more loose or liquid stools per day and/or a daily stool weight greater than 200 g/day, persisting for more than four weeks 1, 2
The four-week duration threshold is the accepted standard that distinguishes chronic from acute diarrhea and suggests a non-infectious etiology requiring further investigation 3, 4, 5

Symptoms persisting beyond four weeks merit systematic evaluation for non-infectious causes including inflammatory bowel disease, microscopic colitis, celiac disease, bile acid diarrhea, malabsorption syndromes, and colorectal neoplasia is not a guideline but rather a medical evaluation 3
Distinguish true diarrhea from functional bowel disorders such as irritable bowel syndrome (IBS), which affects 9-12% of the population and can overlap significantly with chronic diarrhea based on symptom reporting alone 3, 4

Chronic diarrhea affects approximately 4-5% of Western populations when defined by excessive stool frequency without abdominal pain 3
It represents one of the most common reasons for referral to gastroenterology clinics 4, 5

The British Society of Gastroenterology recommends that symptoms persisting for longer than 4 weeks suggest a non-infectious aetiology and merit further investigation 6, 7
The British Society of Gastroenterology (2003) confirms that most groups would accept that symptoms persisting for longer than four weeks suggest a non-infectious aetiology 7

Chronic diarrhea (≥4 weeks) requires systematic investigation for non-infectious causes including inflammatory bowel disease, microscopic colitis, celiac disease, bile acid diarrhea, malabsorption syndromes, and colorectal neoplasia 6, 8, 9

The diagnostic workup for chronic diarrhea should begin with first-line investigations in primary care, including complete blood count, inflammatory markers, celiac serology, thyroid function, and fecal calprotectin 10, 9
The presence of alarm features mandates more urgent and aggressive evaluation including colonoscopy with biopsies 8, 10