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Acute Diarrhea

Basics

Description

  • Abnormal increase in stool water, volume, or frequency (≥3 stools/day above baseline) lasting <14 days
  • Most commonly infectious; frequently self-limited
  • Types:
  • Viral (50–70%): Noninflammatory, watery diarrhea with nausea/vomiting, incubation ~1 day, duration 1–3 days
  • Bacterial (15–20%): Often inflammatory (bloody), incubation varies; symptoms 1–7 days; antibiotics can shorten disease
  • Protozoal (10–15%): Noninflammatory, watery, longer incubation (~7 days), prolonged illness >7 days
  • Traveler’s diarrhea (TD): Onset 3–7 days after travel, usually resolves within 5 days

Epidemiology

  • More common in children in resource-limited countries; no age predilection in resource-rich countries

  • 128,000 hospital admissions annually in U.S.; ~2.5 million deaths worldwide

  • 4th leading cause of death in children <5 years globally
  • Affects 11% of general population worldwide
  • Commonly linked to contaminated food and water in developed countries

Etiology and Pathophysiology

  • Bacterial: E. coli, Salmonella, Shigella, Campylobacter jejuni, Vibrio spp., Clostridium difficile, others
  • Viral: Rotavirus, Norovirus (most common), adenovirus, astrovirus, CMV (immunocompromised)
  • Protozoal: Giardia lamblia, Entamoeba histolytica, Cryptosporidium, Cystoisospora belli, Cyclospora
  • Pathogenesis:
  • Noninflammatory diarrhea: increased secretion without mucosal damage (typically viral)
  • Inflammatory diarrhea: mucosal invasion/damage by invasive/toxin-producing bacteria, bloody stools

Risk Factors

  • Travel to resource-limited areas
  • Poor food/water hygiene
  • Immunocompromised states (HIV, malignancy, chemotherapy)
  • Recent hospitalization or antibiotic use
  • Proton pump inhibitors use
  • Daycare exposure
  • Fecal-oral sexual contact
  • Pregnancy (increased risk of listeriosis)

Prevention

  • Frequent handwashing (reduces incidence by ~30%)
  • Food and water safety ("boil it, peel it, cook it, or forget it")
  • Avoid undercooked meat, raw fish, unpasteurized milk
  • Vaccines: rotavirus (infants), typhoid, cholera (travelers)
  • TD prevention:
  • Pretravel counseling on high-risk foods/beverages
  • Bismuth subsalicylate prophylaxis reduces TD risk by up to 60%
  • Antibiotic prophylaxis discouraged except in select immunocompromised

Diagnosis

History

  • Duration <14 days
  • Dehydration signs: orthostatic hypotension, dizziness, thirst, decreased urine, altered mental status
  • Stool characteristics: volume, frequency, presence of mucus, blood, fat; pale greasy stools (Giardia)
  • Associated symptoms: abdominal pain, bloating, nausea/vomiting, fever
  • Risk factors and comorbidities (cirrhosis, hemochromatosis)

Physical Exam

  • Assess dehydration severity (dry mucosa, tachycardia, orthostatic hypotension)
  • Fever suggests inflammatory cause
  • Abdominal exam for tenderness, rigidity, rebound
  • Rectal exam for blood, stool consistency

Differential Diagnosis

  • Inflammatory bowel disease (IBD), malabsorption
  • Medication-induced diarrhea
  • Diverticulitis, ischemic colitis
  • Fecal impaction
  • Endocrinopathies (thyroid disease)
  • Neoplasia

Diagnostic Tests

  • Labs reserved for moderate-severe cases, immunocompromised, dysentery, persistent symptoms >7 days
  • CBC (leukocytosis, anemia, eosinophilia)
  • Basic metabolic panel (electrolytes, BUN, creatinine)
  • Stool studies:
  • Occult blood, fecal leukocytes
  • Stool culture, ova and parasites
  • Multiplex PCR panels for bacteria, viruses, parasites
  • C. difficile toxin assay in high-risk groups
  • Giardia antigen ELISA (>90% sensitive)
  • Imaging: abdominal x-rays or CT if obstruction or severe pain suspected
  • Endoscopy in persistent or unclear cases; colonoscopy for CMV in immunocompromised

Treatment

General Measures

  • Oral rehydration therapy (ORT) is cornerstone
  • IV fluids if unable to tolerate ORT or severe dehydration
  • Balanced electrolyte solutions preferred in elderly or severe TD

Medications

First Line

  • Empiric antibiotics if systemic infection signs, severe illness, bloody diarrhea, immunocompromised:
  • Fluoroquinolones or macrolides tailored by stool culture
  • Specific treatments:
  • Giardia: Metronidazole 250 mg TID for 5–7 days; Tinidazole 2 g once
  • E. histolytica: Metronidazole 500–750 mg TID for 7–10 days; Tinidazole 2 g daily for 3–5 days
  • Shigella: Ciprofloxacin 500 mg BID 3–5 days; Ceftriaxone 1–2 g IM/IV daily 5 days
  • Campylobacter: Azithromycin 500 mg daily 3–5 days or erythromycin 500 mg QID 5 days
  • C. difficile: Fidaxomicin 200 mg BID 10 days preferred; Vancomycin 125–500 mg QID 10–14 days alternative; fecal transplant for recurrent infection
  • Traveler’s diarrhea: Ciprofloxacin 500 mg BID 1–3 days; Azithromycin 500 mg daily or 1 g daily 1–3 days; Rifamycin or rifaximin regimens; Loperamide can be combined in mild cases

General Considerations

  • Avoid antibiotics for Salmonella unless typhoid fever or immunocompromised
  • Avoid antibiotics for E. coli O157:H7 (risk of HUS)
  • Avoid antimotility agents in febrile, bloody diarrhea or C. difficile colitis due to toxic megacolon risk
  • Antimotility agents may speed recovery in mild TD if combined with antibiotics

Complementary Medicine

  • Bismuth subsalicylate may reduce diarrhea frequency
  • Probiotics recommended for prevention of antibiotic-associated diarrhea and C. difficile recurrence
  • Avoid probiotics in immunocompromised patients

Ongoing Care

Diet

  • Early refeeding encouraged
  • No evidence for BRAT diet superiority
  • Avoid coffee, alcohol, dairy, heavily seasoned foods during active diarrhea

Patient Education

  • Emphasize hygiene and prevention measures

Prognosis

  • Usually self-limited and not life-threatening with adequate hydration

Complications

  • Dehydration, shock, sepsis
  • Hemolytic uremic syndrome with E. coli O157:H7
  • Guillain-Barré syndrome with C. jejuni
  • Reactive arthritis with Salmonella, Shigella, and Yersinia
  • Postinfectious irritable bowel syndrome

References

  1. Hamilton KW, Cifu AS. Diagnosis and management of infectious diarrhea. JAMA. 2019;321(9):891-892.
  2. Ferris A, Gaisinskaya P, Nandi N. Approach to diarrhea. Prim Care. 2023;50(3):447-459.
  3. Khanna S, Shin A, Kelly CP. Management of Clostridium difficile infection in inflammatory bowel disease: expert review from the Clinical Practice Updates Committee of the AGA Institute. Clin Gastroenterol Hepatol. 2017;15(2):166-174.

See Also

Codes

  • ICD10: R19.7 Diarrhea, unspecified
  • ICD10: A09 Infectious gastroenteritis and colitis, unspecified
  • ICD10: A08.4 Viral intestinal infection, unspecified

Clinical Pearls

  • Viral causes are the most common etiology in the US
  • Consider broad infectious causes in immunocompromised patients
  • Oral rehydration remains the most effective treatment
  • Avoid antimotility agents in febrile, bloody diarrhea or antibiotic-associated colitis
  • Stool cultures should be reserved for dysentery, fever, severe or prolonged symptoms, or immunosuppression
  • Empiric antibiotics indicated in severe illness or immunocompromise only