Diarrhea, Acute

Basics

An abnormal increase in stool water content, volume, or frequency (≥3 stools above baseline in 24 hours) for <14 days duration
Most commonly secondary to infectious etiology; often self-limited
Acute viral diarrhea (50–70%)
- Most common cause of infectious diarrhea; noninflammatory (watery)
- Frequently presents with associated nausea and/or vomiting
- Symptoms usually develop after an incubation period of ~1 day and last for 1 to 3 days; typically self-limited
Bacterial diarrhea (15–20%)
- Most common infectious cause of inflammatory (bloody) diarrhea
- Incubation period variable; diarrhea caused by preformed enterotoxin presents within 1 to 6 hours of contaminated food ingestion, whereas bacterial infection typically presents within 1 to 3 days.
- Symptoms usually resolve in 1 to 7 days; antibiotic use attenuates length and/or severity of disease.
- Suspect when concurrent illness in others who have shared potentially contaminated food.
Protozoal infections (10–15%)
- Typically, cause noninflammatory (watery) diarrhea
- Long incubation period and prolonged disease course, symptoms develop approximately 7 days after exposure and commonly last >7 days.
- Suspect when outbreaks of watery diarrhea in areas with contaminated water or food supply.
Traveler’s diarrhea (TD) typically begins 3 to 7 days after arrival in foreign location and resolves within 5 days; rapid onset, generally self-limited

In resource-limited countries, acute diarrhea is more common in children; no age predilection in resource-rich countries
Acute diarrhea accounts for >128,000 U.S. hospital admissions and ~2.5 million annual deaths worldwide (1).
The WHO categorizes acute diarrhea (symptoms <14 days) into watery and bloody (dysentery) subtypes.

Fourth leading cause of death in children <5 years old and eighth leading cause of death among all ages worldwide
Affects 11% of the general population
In resource-rich countries, acute diarrhea is largely due to contaminated food and water.
With improvements in sanitation and more widespread use of oral rehydration solution, death rates from diarrhea have declined. Nevertheless, nearly 7 billion cases of diarrheal disease occur worldwide each year.

Bacterial
- Escherichia coli, Salmonella, Shigella, Campylobacter jejuni (most common bacterial causes)
- Vibrio parahaemolyticus, Vibrio cholerae, Yersinia enterocolitica
- Clostridioides difficile, Staphylococcus aureus
- Bacillus cereus, Clostridium perfringens
- Listeria monocytogenes
- Aeromonas species
Viral
- Norovirus (most common overall cause of acute infectious diarrhea)
- Rotavirus (children)
- Adenovirus
- Sapovirus
- Cytomegalovirus (in immunocompromised)
- Herpes simplex virus
Protozoal
- Giardia lamblia, Entamoeba histolytica
- Cryptosporidium (in immunocompromised)
- Cyclospora, Microspora (in immunocompromised)
Pathophysiology (1)
- Noninflammatory: most commonly viral; increased intestinal secretions without disruption of intestinal mucosa; watery character
- Inflammatory: generally invasive or toxin-producing bacteria; disrupts mucosal integrity with subsequent tissue invasion/damage; bloody character
Viral diarrhea: changes in small intestine cell morphology, including villous shortening, increased number of crypt cells, and increased cellularity of the lamina propria
Bacterial diarrhea: Bacterial invasion of colonic wall leads to mucosal hyperemia, edema, and leukocytic infiltration.

Frequent handwashing reduces incidence of diarrhea by approximately 30%.
Proper food and water precautions, particularly during foreign travel—“boil it, peel it, cook it, or forget it”
Avoid undercooked meat, raw fish, unpasteurized milk.
Rotavirus vaccine to all infants without a known contraindication
Typhoid and cholera vaccine (for travel to endemic areas)
TD prevention:
- Pretravel counseling on high-risk food/beverage
- Bismuth subsalicylate (BSS) may reduce the incidence of TD by up to 50%. Despite this, it is still not commonly used as prophylaxis (contraindicated in patients aspirin allergy, gout, renal insufficiency).
- Routine antibiotic prophylaxis is not indicated in the vast majority of cases. Consider rifaximin and rifamycin SV in the rare case prophylaxis if indicated.
- Probiotics, prebiotics, and synbiotics have unclear benefit as prophylaxis.

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