Gastro 2013 APDW/WCOG Shanghai Working Party Report: Chronic diarrhea: Definition, classification, diagnosis

TL;DR

This working party report reviews definitions, classification, and diagnostic evaluation of chronic diarrhea, concluding that a 4-week duration cutoff is arbitrary and that careful history plus targeted testing remains central. It surveys classification by pathophysiology and stool characteristics and assesses stool, serologic, breath, bile acid, pancreatic, imaging, endoscopic, and biopsy tests, highlighting gaps and limited utility of many tests.

Key findings

• Chronic diarrhea is less frequent than acute diarrhea; 3–5% of the population may have diarrhea lasting more than 1 month in any given year. Normal stool output averages approximately 100 g/day, with an upper 95% confidence limit of roughly 200 g/day, though up to 300 g may be normal on a high-fiber diet; about 20% of patients referred to one tertiary center for chronic diarrhea had normal stool weight.
• IBS and functional diarrhea are the most common causes of chronic diarrhea in Western populations. IBS onset averaged 38 ± 14 years in one large study, while microscopic colitis averaged 57 ± 13 years; IBS shows a female predominance with a sex ratio of 3:1 in primary care consulters. Microscopic colitis accounted for 10% of chronic diarrhea cases in patients over 70 years in Sweden.
• Fecal osmotic gap helps classify watery diarrhea: a gap < 50 mOsm/kg is characteristic of secretory diarrhea, and a gap > 75 mOsm/kg is characteristic of osmotic diarrhea.
• Breath test performance is variable: glucose hydrogen breath tests for small intestinal bacterial overgrowth had reported sensitivity 27–93% and specificity 30–86%, while lactulose hydrogen breath tests had sensitivity 17–89% and specificity 44–100%. Capsule endoscopy retention occurred in 1.3% of patients in one retrospective Swedish study and may be as high as 13% in known Crohn’s disease.

Methods

• Design: Working party report/consensus review from the Gastro 2013 APDW/WCOG Shanghai Working Party, proposed by the American College of Gastroenterology to the World Gastroenterology Organisation, to examine definitions, classification, and diagnosis of chronic diarrhea.
• Data and analysis: Narrative synthesis of existing literature and expert consensus; no primary data collection, systematic search strategy, or formal meta-analysis is reported. The report assesses diagnostic tests and highlights knowledge gaps and research opportunities.

Limitations

• Stated: the definition of chronic diarrhea remains debated, with loose stool form, increased frequency, stool weight, and duration criteria all at best arbitrary; most studies used to define the 4-week cutoff were done in industrialized countries, and information from less developed regions is needed.
• Stated: classification schemes need to be judged by their utility in individual patients who may not fit distinct categories; no simple diagnostic algorithm is currently possible because of the number of possible diagnoses, limited appreciation of pretest probabilities that depend on geography and patient specifics, variable test availability and performance, and costs.
• Evident from the text: as a narrative working party report, it does not provide a systematic review, formal evidence grading, or prospective validation of the proposed definitions and diagnostic approaches.