Chronic Diarrhea

Assess volume status, orthostasis, urine output, serum creatinine, potassium, bicarbonate, and other basic metabolic panel abnormalities at presentation when stool losses are clinically consequential. Chronic diarrhea can produce dehydration, hypokalemia, non-anion-gap metabolic acidosis, and prerenal or multifactorial acute kidney injury; these findings warrant fluid and electrolyte replacement while the diagnostic workup proceeds. ccjm+1ccjm[PDF] A 56-year-old with diarrhea and weaknessPubMedChronic Diarrhea in Adults: Evaluation and Differential Diagnosis - PubMed

Escalate beyond a functional-disorder pathway when there is marked weight loss, greasy stools, nutritional deficiency, bleeding, systemic illness, or evidence of intestinal inflammation. Structural, inflammatory, infectious, malignant, malabsorptive, pancreatic, endocrine, medication-related, postoperative, and gut-brain interaction disorders can overlap symptomatically; diagnostic categorization should be driven by stool phenotype and targeted clinical clues rather than a presumptive IBS-D diagnosis. ScienceDirect+3ScienceDirectApproach to the adult patient with chronic diarrheaScienceDirectChronic Diarrhea - an overviewWolters KluwerDifferential Diagnosis of Chronic Diarrhea: An Algorithm to ... : Journal of Clinical GastroenterologyPubMedChronic Diarrhea in Adults: Evaluation and Differential Diagnosis - PubMed

Document onset as abrupt versus gradual, continuous versus intermittent, and relation to medications, toxic exposures, alcohol, prior surgery, infection, or altered bowel anatomy. These exposures separate common secondary causes—medication effects, laxatives, postoperative physiology, postinfectious disease, and malabsorption—from primary inflammatory or functional disorders. ScienceDirect+3ScienceDirectAmerican Gastroenterological Association medical position statement: Guidelines for the evaluation and management of chronic diarrheaScienceDirectApproach to the adult patient with chronic diarrheaScienceDirectChronic Diarrhea - an overviewWolters KluwerDifferential Diagnosis of Chronic Diarrhea: An Algorithm to ... : Journal of Clinical Gastroenterology

For adults with chronic watery diarrhea compatible with functional diarrhea or IBS-D and without alarm features, order IgA tissue transglutaminase antibody with total IgA, test for Giardia, and obtain a fecal inflammatory marker such as calprotectin or lactoferrin. If IgA deficiency is present, use IgG tissue transglutaminase and IgG or IgA deamidated gliadin peptide testing for celiac disease. NEJM+1NEJMTesting for Functional Diarrhea and Diarrhea-Predominant Irritable Bowel Syndrome | NEJM ClinicianWolters KluwerDifferential Diagnosis of Chronic Diarrhea : Journal of Clinical Gastroenterology

Avoid an indiscriminate "kitchen sink" approach in the low-alarm IBS-D or functional-diarrhea phenotype. AGA-oriented guidance favors celiac disease testing, Giardia assessment, and stool inflammatory markers first; subsequent testing should be determined by the phenotype and initial results. NEJM+1NEJMTesting for Functional Diarrhea and Diarrhea-Predominant Irritable Bowel Syndrome | NEJM ClinicianWolters KluwerDifferential Diagnosis of Chronic Diarrhea : Journal of Clinical Gastroenterology

A positive fecal calprotectin or lactoferrin changes the pathway from functional disease to inflammatory evaluation. Fecal calprotectin is a noninvasive marker of gastrointestinal inflammation, but it is not disease-specific; interpret an abnormal test in the context of IBD, infection, ischemic colitis, microscopic colitis, and colorectal neoplasia risk, then select endoscopy, biopsy, or pathogen testing accordingly. ScienceDirect+2ScienceDirectChronic Diarrhea - an overviewPubMedFecal calprotectin and elastase 1 determinations in patients with pancreatic diseases: a possible link between pancreatic insufficiency and intestinal inflammation - PubMedPubMedChronic Diarrhea in Adults: Evaluation and Differential Diagnosis - PubMed

When the differential remains broad after history, examination, and baseline blood testing, classify stool as watery, fatty, or inflammatory. This practical classification directs subsequent testing and accommodates overlap, since individual disorders may generate more than one pattern. PubMedPubMedChronic Diarrhea in Adults: Evaluation and Differential Diagnosis - PubMed

Diagnose IBS-D or functional diarrhea only after targeted exclusion of celiac disease, Giardia infection, and intestinal inflammation in an appropriate low-alarm presentation. Organic disorders that can resemble IBS include celiac disease, IBD, colorectal cancer, chronic gastrointestinal infection, microscopic colitis, and primary bile acid diarrhea. NEJM+2NEJMTesting for Functional Diarrhea and Diarrhea-Predominant Irritable Bowel Syndrome | NEJM ClinicianThe LancetThe overlap between irritable bowel syndrome and organic gastrointestinal diseasesWolters KluwerDifferential Diagnosis of Chronic Diarrhea : Journal of Clinical Gastroenterology

Consider bile acid diarrhea in persistent unexplained watery diarrhea, including patients otherwise labeled IBS-D. Testing options cited in current diagnostic pathways include a 48-hour fecal bile acid assay and serum fibroblast growth factor 19 measurement; an empiric bile acid binder trial may be a reasonable concomitant or subsequent strategy when diagnostic testing is unavailable or not widely accessible. NEJM+1NEJMTesting for Functional Diarrhea and Diarrhea-Predominant Irritable Bowel Syndrome | NEJM ClinicianWolters KluwerDifferential Diagnosis of Chronic Diarrhea : Journal of Clinical Gastroenterology

In older adults with chronic watery diarrhea, proceed to endoscopic evaluation with biopsy to exclude microscopic colitis even when the mucosa appears normal. Microscopic colitis is defined histologically in the setting of chronic watery diarrhea and can lack significant colonoscopic abnormalities, so normal visual inspection alone does not exclude it. NEJM+1NEJMTesting for Functional Diarrhea and Diarrhea-Predominant Irritable Bowel Syndrome | NEJM ClinicianNature54 XXVI Congress of the IAP: Abstracts

Review osmotic contributors before escalating invasive testing: lactose or other carbohydrate malabsorption, sorbitol and other sugar alcohols, laxatives, and antacids are recognized causes of osmotic diarrhea. A carefully timed withdrawal or dietary exposure assessment is often more decision-relevant than broad biomarker testing when the history identifies a plausible agent. ScienceDirectScienceDirectChronic Diarrhea - an overview

Treat greasy stool and marked weight loss as a malabsorption signal. Celiac disease is a key cause of chronic fatty diarrhea and can produce laboratory evidence of malabsorption; initial testing uses tissue transglutaminase IgA with total IgA, with IgG-based serologies in IgA deficiency. NEJM+2NEJMTesting for Functional Diarrhea and Diarrhea-Predominant Irritable Bowel Syndrome | NEJM Clinicianccjm[PDF] A 56-year-old with diarrhea and weaknessPubMedChronic Diarrhea in Adults: Evaluation and Differential Diagnosis - PubMed

Evaluate pancreatic exocrine insufficiency when diarrhea is accompanied by maldigestive symptoms, nutritional abnormalities, or pancreatic risk factors. Fecal elastase-1 is the commonly used indirect test, whereas direct secretin-cholecystokinin testing is invasive, costly, cumbersome, and generally reserved for selected functional assessment of chronic pancreatitis rather than routine exocrine insufficiency diagnosis. Wolters KluwerWolters KluwerDifferential Diagnosis of Chronic Diarrhea: An Algorithm to ... : Journal of Clinical Gastroenterology

For inflammatory diarrhea, use fecal calprotectin or lactoferrin as a noninvasive screen and pursue endoscopic evaluation when clinical findings or biomarkers suggest intestinal inflammation. The differential includes Crohn disease, ulcerative colitis, infectious colitis, ischemic colitis, microscopic colitis, and colorectal malignancy. ScienceDirect+3ScienceDirectChronic Diarrhea - an overviewWolters KluwerDifferential Diagnosis of Chronic Diarrhea: An Algorithm to ... : Journal of Clinical GastroenterologyPubMedFecal calprotectin and elastase 1 determinations in patients with pancreatic diseases: a possible link between pancreatic insufficiency and intestinal inflammation - PubMedPubMedChronic Diarrhea in Adults: Evaluation and Differential Diagnosis - PubMed

Use stool pathogen testing selectively rather than assuming chronic bacterial infection. Giardia is specifically prioritized in guideline-based functional-diarrhea and IBS-D evaluation, while broader stool culture, ova and parasite examination, and specialized testing are driven by clinical context and potential exposure to persistent pathogens. NEJM+1NEJMTesting for Functional Diarrhea and Diarrhea-Predominant Irritable Bowel Syndrome | NEJM ClinicianScienceDirectAmerican Gastroenterological Association medical position statement: Guidelines for the evaluation and management of chronic diarrhea

Proceed to colonoscopy with biopsies when chronic diarrhea is accompanied by alarm features, an inflammatory phenotype, concern for colorectal cancer or IBD, or persistent watery diarrhea in an older adult where microscopic colitis is plausible. Biopsy is essential for microscopic colitis because diagnostic mucosal inflammation may occur without significant endoscopic abnormalities. NEJM+3NEJMTesting for Functional Diarrhea and Diarrhea-Predominant Irritable Bowel Syndrome | NEJM ClinicianThe LancetThe overlap between irritable bowel syndrome and organic gastrointestinal diseasesNature54 XXVI Congress of the IAP: AbstractsScienceDirectChronic Diarrhea - an overview

Use specialized pancreatic testing sparingly. Direct secretin-cholecystokinin testing and endoscopic pancreatic function testing are invasive or not routinely available and are principally used when assessing chronic pancreatitis with inconclusive imaging, not as first-line tests for exocrine pancreatic insufficiency. Wolters KluwerWolters KluwerDifferential Diagnosis of Chronic Diarrhea: An Algorithm to ... : Journal of Clinical Gastroenterology

Refer persistent unexplained cases for mechanism-focused evaluation rather than repeating the same low-yield screening tests. The next branch should be selected from the unresolved phenotype: bile acid diarrhea testing for watery stool, biopsy for microscopic colitis, pancreatic assessment for fatty stool, or endoscopic inflammatory evaluation for abnormal calprotectin or lactoferrin. NEJM+3NEJMTesting for Functional Diarrhea and Diarrhea-Predominant Irritable Bowel Syndrome | NEJM ClinicianWolters KluwerDifferential Diagnosis of Chronic Diarrhea : Journal of Clinical GastroenterologyWolters KluwerDifferential Diagnosis of Chronic Diarrhea: An Algorithm to ... : Journal of Clinical GastroenterologyPubMedChronic Diarrhea in Adults: Evaluation and Differential Diagnosis - PubMed

Monitor the consequences of ongoing stool loss during the diagnostic interval. Recheck renal function, electrolytes, and acid-base status when initial testing shows volume depletion, potassium loss, metabolic acidosis, or kidney injury, because correction of these abnormalities is independent of the eventual etiologic diagnosis. ccjm+1ccjm[PDF] A 56-year-old with diarrhea and weaknessPubMedChronic Diarrhea in Adults: Evaluation and Differential Diagnosis - PubMed