From the Guidelines
For the evaluation of chronic diarrhea, I strongly recommend starting with a comprehensive stool study, including fecal calprotectin, fecal lactoferrin, stool culture, ova and parasite examination, Clostridioides difficile toxin, and fecal occult blood test, as well as celiac disease screening with tissue transglutaminase antibodies and total IgA levels, based on the most recent guidelines from the American Gastroenterological Association 1.
When evaluating chronic diarrhea, it is essential to consider a stepwise diagnostic approach, starting with basic tests and progressing to more specialized ones based on initial findings. The initial evaluation should include a detailed history and physical examination to identify potential causes of diarrhea, such as recent travel, antibiotic use, or exposure to infectious agents.
Some key points to consider in the diagnostic workup of chronic diarrhea include:
- Stool testing for infectious causes, such as Giardia, as recommended by the American Gastroenterological Association 1
- Evaluation for malabsorptive causes, such as celiac disease, with tissue transglutaminase antibodies and total IgA levels 1
- Assessment for inflammatory causes, such as inflammatory bowel disease, with fecal calprotectin and fecal lactoferrin 1
- Consideration of bile acid malabsorption, particularly in patients with a history of gastrointestinal surgery or disease 1
The British Society of Gastroenterology guidelines also emphasize the importance of a detailed history and examination in the assessment of patients with chronic diarrhea, including the evaluation of alarm features, such as nocturnal diarrhea, weight loss, and abdominal pain 1.
In terms of specific tests, the guidelines recommend the use of fecal calprotectin or fecal lactoferrin to screen for inflammatory bowel disease 1, as well as testing for Giardia and celiac disease 1. The guidelines also suggest against the use of ESR or CRP to screen for inflammatory bowel disease, unless there are other indications for these tests 1.
Overall, a comprehensive and stepwise approach to the evaluation of chronic diarrhea is essential to identify the underlying cause and guide targeted treatment, as highlighted by the American Gastroenterological Association 1 and the British Society of Gastroenterology 1.
From the Research
Initial Evaluation
To evaluate chronic diarrhea, the following tests can be ordered:
- Complete blood count
- C-reactive protein
- Anti-tissue transglutaminase immunoglobulin A (IgA)
- Total IgA
- Basic metabolic panel 2 These tests can help identify pathologies such as celiac disease or inflammatory bowel disease.
Categorizing Diarrhea
Diarrhea can be categorized into:
- Watery diarrhea (secretory, osmotic, or functional)
- Fatty diarrhea (malabsorption or maldigestion)
- Inflammatory diarrhea 2 This categorization can help guide further testing and treatment.
Targeted Testing
Targeted testing should be based on the differential diagnosis and may include:
- Stool studies to categorize diarrhea
- Endoscopy
- Imaging studies
- Histology
- Physiological testing 3 These tests can help identify the underlying cause of chronic diarrhea.
Specific Diagnostic Investigation
Specific diagnostic investigation can be reserved for patients with:
- Severe dehydration
- More severe illness
- Persistent fever
- Bloody stools
- Immunosuppression
- Suspected nosocomial infection or outbreak 4 This investigation may include tests such as stool culture, C. difficile testing, PCR, ova and parasites' search, endoscopy, and abdominal imaging.
Routine Laboratory Tests
Routine laboratory tests can help in categorizing diarrhea and may include:
- Complete blood count
- Creatinine and electrolytes evaluation
- Determination of leukocytes and lactoferrin presence in the stools 4, 5 These tests can provide valuable information about the underlying cause of chronic diarrhea.
Reducing Inappropriate Testing
Inappropriate stool testing, such as stool cultures and ova and parasite testing, can be reduced by:
- Implementing best practice advisories within the electronic medical record
- Educating healthcare providers about the low yield of these tests in certain situations 6 This can help reduce unnecessary testing and improve patient care.