Noninflammatory diarrhea	Inflammatory diarrhea
Etiology	Infectious: often viral, but may be bacterial and, less likely, parasitic Noninfectious: dietary, psychosocial stressors	Infectious: frequently invasive or toxin-producing bacteria Noninfectious: Crohn disease, ulcerative colitis, radiation enteritis
History and examination	Infectious: nausea, vomiting, abdominal discomfort Noninfectious: nausea, abdominal discomfort, frequently without vomiting	Infectious: fever, abdominal pain, tenesmus, systemic signs and symptoms Noninfectious: abdominal pain, tenesmus, fatigue, weight loss
Laboratory findings	Infectious: often not performed; positive PCR or NAAT result Noninfectious: negative PCR or NAAT result, positive specific laboratory testing (e.g., antitissue transglutaminase antibody)	Infectious: positive PCR or NAAT result Noninfectious: negative PCR or NAAT result; positive for fecal calprotectin*
Common infectious pathogens	Bacterial: enterotoxigenic Escherichia coli, Clostridium perfrin-gens, Bacillus cereus, Staphylococcus aureus, Vibrio cholerae Viral: Rotavirus, Norovirus Parasitic: Giardia, Cryptosporidium	Bacterial: Salmonella, Shigella, Campylobacter, Shiga toxin–producing E. coli, entero-invasive E. coli, Clostridioides difficile, Yersinia Parasitic: Entamoeba histolytica