Diarrhea Without Fever: Differential Diagnoses and Management

Introduction to Differential Diagnoses

The American College of Physicians and the Infectious Diseases Society of America recommend prioritizing viral gastroenteritis, STEC infection, parasitic infections, toxin-mediated bacterial illness, and non-infectious causes in the differential diagnosis of diarrhea without fever 1, 2, 3

STEC characteristically presents without fever at the time of presentation, despite causing severe abdominal pain and often grossly bloody stools, as noted by the Centers for Disease Control and Prevention 1, 2, 4
Viral gastroenteritis typically causes low-grade or no fever, with vomiting and nonbloody diarrhea lasting 2-3 days, according to the World Health Organization 1, 2, 3
Toxin-mediated bacterial illness presents with nausea, vomiting, and diarrhea lasting ≤24-48 hours without significant fever, as reported by the European Centre for Disease Prevention and Control 1, 2

Norovirus is the leading cause of acute gastroenteritis in the United States, presenting as acute watery diarrhea without blood, often with vomiting, and is self-limited, as stated by the Centers for Disease Control and Prevention 3
STEC, especially O157:H7, is characterized by severe abdominal pain with bloody stools but minimal or no fever, as noted by the Infectious Diseases Society of America 1, 2, 4
Giardia lamblia and Cryptosporidium are the most common parasitic causes of persistent or chronic diarrhea, presenting with symptoms lasting ≥14 days, according to the World Health Organization 1, 2, 3

Antibiotic-associated diarrhea should be tested for C. difficile if antibiotic use occurred within the preceding 8-12 weeks, though C. difficile can present with or without fever, as recommended by the Infectious Diseases Society of America 6, 3, 4
Irritable bowel syndrome is distinguished by pain that peaks before defecation, is relieved by defecation, and is associated with changes in stool form or frequency, as defined by the Rome criteria 6

If bloody stools are present, test for STEC as the primary concern, and consider Salmonella, Shigella, Campylobacter, and Entamoeba histolytica, as recommended by the Centers for Disease Control and Prevention 1, 2, 3, 5
If watery, nonbloody stools are present, consider viral gastroenteritis, toxin-mediated bacterial illness, and Vibrio species, as noted by the European Centre for Disease Prevention and Control 1, 2, 3

Stool testing is indicated even without fever if bloody or mucoid stools are present, severe abdominal cramping or tenderness occurs, or the patient is immunocompromised, as recommended by the Infectious Diseases Society of America 1, 3, 6

Bloody diarrhea with anemia, thrombocytopenia, or renal dysfunction requires urgent evaluation for hemolytic uremic syndrome, as noted by the American College of Physicians 3, 4
Unintentional weight loss with bloody stools requires consideration of colorectal cancer, as recommended by the American Cancer Society 3

Empiric antibiotics should not be given in immunocompetent patients with bloody diarrhea while awaiting test results, as this increases the risk of hemolytic uremic syndrome, as warned by the Centers for Disease Control and Prevention 5, 3, 4