Acute Diarrhea in Adults

Acute Diarrhea in AdultsAcute Diarrhea in Adults


Acute diarrheal disease is a common condition encountered in the acute setting. Acute Diarrhea is defined as the presence of three or more loose or watery stools in a period of a day lasting seven days. Acute diarrhea can be classified into inflammatory or non-inflammatory according to the characteristics of the depositions and the patient’s clinical condition.

Diagnosis of acute diarrhea in adults is mainly clinical, with ancillary tests performed for assessing hydration status, electrolyte balance, and complications associated with the acute infection. Microbiological studies are performed in selected cases, such as that of Clostridium difficile diarrhea.

Treatment is mainly symptomatic, addressing the rehydration of the patient by oral or intravenous rehydration strategies. Antibiotic treatment is reserved for selected cases.

Acute Diarrhea in Adults – Introduction

Acute diarrheal disease is a common and very frequent cause of outpatient clinic visits and hospitalizations. Every year, almost 2 billion cases of diarrheal disease occur worldwide, according to UNICEF and the World Health Organization (WHO). (1, 2)

In the United States alone, there are approximately 179 million outpatient visits, 500.000 hospitalizations, and around 5.000 deaths from acute diarrheal disease per year. (3-5)

Causes of diarrhea can include either infectious or noninfectious causes and can be further classified as inflammatory or noninflammatory. The most common presentation of diarrheal disease is infectious noninflammatory diarrhea, which usually has a viral etiology; nonetheless, bacterial and parasitic causes are also frequent and often related to travel or foodborne illness. (2, 3)

Definition of Acute Diarrhea

Diarrhea is characterized by the passage of three or more loose or watery stools in a period of 24 hours. (2-4)

According to its duration, diarrhea can be classified as:

  • Acute: when symptoms last fewer than two weeks. It is important to note that some bibliographies define diarrhea that lasts less than seven days as acute, while diarrhea that lasts seven to fourteen days is considered prolonged. (3, 4, 6)
  • Persistent: when symptoms of diarrhea last fourteen to thirty days. (3, 4)
  • Chronic: when diarrhea symptoms last longer than one month. (3, 4)

Diarrhea can also be categorized as:

  • Inflammatory: also called dysentery, is generally accompanied by blood or mucus and is usually caused by invasive microorganisms or processes. (3, 7)
  • Noninflammatory: usually watery; it is often caused by either decreased water reabsorption or increased water secretion into the intestinal lumen. (3, 7)

Etiology of Acute Diarrhea

In the United States, the burden of foodborne illness is around 48 million cases each year, constituting around 36% of all cases of diarrhea. The most common source of foodborne-infection diarrhea is produced, usually by contaminated leafy green vegetables. (4)

Noroviruses are the main cause of diarrhea due to foodborne infection, and they are responsible for roughly 50% of diarrhea outbreaks, 26% of diarrhea cases in emergency rooms, and 13% of office visits due to diarrhea. (4, 8, 9)

The most prevalent cause of nosocomial infectious diarrhea is Clostridium difficile infection, which can result in severe complications, including death. (4, 10)

Risk Factors for Acute Diarrhea

Factors that increase the risk of developing infectious diarrhea include:

  • Advanced age, which is also an independent risk factor for the severity of diarrhea. In the United States, adults 65 years of age or older account for approximately 83% of deaths due to acute diarrhea. (10)
  • Decrease in immune function, either due to drugs or disease.
  • Use of medications that alter the intestinal flora and gut homeostasis, including proton-pump inhibitors, acid-reducing agents, chemotherapy, and antibiotics. (4, 11)
  • Recent international travel.
  • Unsafe sexual practices.
  • Day-care center workers.
  • Working or living in closed populations, such as nursing homes, cruise ships, hospitals, or dormitories. (1, 4, 12)

Diagnosis and Management of Acute Diarrhea

In countries with appropriate food and water sanitation, most acute diarrhea episodes are self-limited and uncomplicated; therefore, supportive treatment is usually the only warranted intervention. However, when mucus or blood (bright red from blood or black from melena) is detected or when a risk factor is present, additional diagnostic evaluation and management may be necessary. (3, 4)

Initial evaluation of patients with acute diarrhea should include the onset of symptoms, stool character, frequency of episodes, a focused review of systems, and evaluation of risk factors. Physical examination of these patients must include evaluation for signs of dehydration, infectious processes, or potential surgical complications; it is imperative to evaluate the patient’s vital signs, mucous membranes, sensorium, presence of fever or postural hypotension, and perform a rectal examination to assess for gross and occult blood in the feces. (3, 4, 7, 12)

The presence of grossly bloody stools accompanied by fever and systemic toxicity should be considered a warning sign of complicated illness or bacteriemia, as this generally points to infections due to invasive pathogens, such as Salmonella, Entamoeba histolytica, Shigella, or Campylobacter jejuni. (1, 4)

If vomiting is present, the most likely cause is viral gastroenteritis or food poisoning. In outbreaks, the incubation period can be useful to determine the possible etiology and differentiate between food poisoning (2 to 7 hours) and viral infection (more than 14 hours, usually 24 to 48 hours). (4)

Management of acute diarrhea must begin with rehydration and replenishment of electrolytes and nutrients. If tolerated, oral hydration is preferred, but in the case of frequent and persisting vomiting (>4 episodes per hour) or if signs of severe dehydration or sepsis are present, intravenous hydration is warranted. Nevertheless, if intravenous hydration is not possible, nasogastric administration of oral rehydration solution is a potentially lifesaving alternative until the patient can receive appropriate treatment. (1, 4, 11, 13, 14)

In the initial stages of rehydration therapy, adults can drink up to 750 ml of oral rehydration solution (ORS) per hour and up to roughly 4000 ml in 4 hours. (15)

If severe dehydration or hypovolemic shock ensues and intravenous hydration is necessary, start administering Ringer’s Lactate Solution (also called Hartmann’s Solution for Injection) as follows: first, give 30 ml/kg in a 30-minute period (repeating once if the radial pulse is weak or not detectable), then give 70 ml/kg in 2 and a half hours. Reevaluate the patient every 1 to 2 hours. Administer the IV drip more rapidly if the hydration status is not improving. (15)

Normal feeding should be encouraged for patients with no overt signs of dehydration, and feeding should be established as soon as possible after correction of moderate and severe dehydration. Even though the avoidance of dairy and the BRAT diet (bananas, rice, applesauce, and toast) is a common recommendation, supporting evidence for these interventions is limited. (13,16)

Antibiotic therapy is rarely needed but may be appropriate following a microbiologic stool examination. To help decrease inappropriate antibiotic use, antimotility agents can be useful as a symptomatic therapy for acute watery diarrhea but must be avoided when bloody diarrhea is present. (3, 7, 12, 16)

In the case of travelers’ diarrhea, antibiotic treatment and the addition of loperamide decreases the duration of symptoms and increase the probability of a cure. Simethicone, along with loperamide, may provide a resolution to watery diarrhea and abdominal pain compared to each treatment alone. (3)

Complementary Studies

Since most cases of acute diarrhea are self-limited, testing is usually not indicated. Complementary tests should be reserved for outbreaks or suspected nosocomial infections; further studies may also be warranted for patients with bloody stool, persistent fever, severe dehydration, severe illness, or immunosuppression. (1, 4, 14, 16)

Stool cultures are usually unnecessary except in case of clinical or epidemiological suspicion of cholera and to identify the pathogen causing dysentery. (1, 16)

Fecal occult blood is a rapid and inexpensive test that is highly specific and sensitive for inflammatory diarrhea, while a lactoferrin test is a fast and simple method to identify the presence of leukocytes in the stool, which increases in the setting of bacterial infections. (1, 16)

Indications for Clostridium difficile toxins testing include suspected nosocomial diarrhea and cases where patients develop diarrhea in the context of current antibiotic use or in the last three months of antibiotic treatment. (16)

Testing for ova and parasites is suggested in cases of persistent diarrhea lasting more than one week, patients with AIDS, men who have sex with men, community waterborne outbreaks, and in cases of bloody diarrhea with few fecal leukocytes. (16)

Differential Diagnosis of Acute Diarrhea

Several specific exposures or conditions can be closely related to certain pathogens, such as: (13)

  • Foodborne outbreaks in crowded places such as restaurants, hotels, resorts, cruise ships, etc.: Norovirus, shigella, Listeria, non-typhoidal Salmonella, Staphylococcus aureus, Campylobacter spp, Cryptosporidium spp, Clostridium perfringens, Bacillus cereus, enterotoxigenic Escherichia coli, Shiga toxin-producing Escherichia coli, Cyclospora cayetanensis.
  • Eating or drinking unpasteurized milk or dairy products: Salmonella, S. aureus toxin, Yersinia enterocolitica, Campylobacter, Cryptosporidium, and Shiga toxin–producing Escherichia coli. Brucella (goat milk cheese), Coxiella burnetii, Mycobacterium bovis.
  • Eating raw or undercooked meat, poultry, eggs, or shellfish: Salmonella, Shiga toxin–producing Escherichia coli, Yersinia, C. perfringens, Campylobacter, S. aureus, and Trichinella spp. (meat or poultry); Salmonella or Shigella (eggs); and Vibriospecies, Norovirus, Hepatitis A virus, and Plesiomonas (shellfish).
  • Eating or drinking vegetables, sprouts, fruits, or unpasteurized fruit juices: Hepatitis A virus, Shiga toxin–producing Escherichia coli, Cryptosporidium, Norovirus, non-typhoidal Salmonella, Cyclospora, and Listeria monocytogenes.
  • Swimming in or drinking untreated fresh water: Giardia, Salmonella, Shigella, Campylobacter, Cryptosporidium, Shiga toxin–producing Escherichia coli, and Plesiomonas shigelloides.
  • Healthcare, long-term care, childcare center attendance or employment, prison exposure or employment: Norovirus, Clostridium difficile, Shigella, Cryptosporidium, Giardia, Shiga toxin–producing Escherichia coli, Rotavirus.
  • Recent travel to resource-challenged countries: Escherichia coliVibrio choleraeGiardia, Cyclospora, Entamoeba histolytica, ShigellaBlastocystis, Typhi and non-typhoidal Salmonella, Campylobacter, Cystoisospora, and
  • Visiting a farm or petting zoo: Shiga toxin–producing Escherichia coli, Cryptosporidium, Campylobacter.
  • Exposure to pets with diarrhea: Campylobacter, Yersinia.

Inflammatory and noninflammatory diarrhea can have infectious and noninfectious causes. Characteristics of inflammatory and noninflammatory diarrhea can be resumed as follows:

  • Inflammatory diarrhea, infectious:

Infectious inflammatory diarrhea is usually severe and is frequently caused by invasive or toxin-producing bacteria, such as Salmonella, Shigella, Yersinia, Campylobacter, entero-invasive E. coli, Shiga toxin–producing E. coli, or Clostridioides difficile. Entamoeba histolytica is also a frequent parasitic cause. Physical examination can reveal abdominal pain, fever, tenesmus, bloody stools, and systemic signs and symptoms. Laboratory findings include positive PCR or NAAT results.

  • Inflammatory diarrhea, noninfectious:

Noninfectious inflammatory diarrhea can happen due to Crohn’s disease, ulcerative colitis, or radiation enteritis, among others. Physical findings include fatigue, abdominal pain, tenesmus, and weight loss. Laboratory tests include negative PCR or NAAT results and positive fecal calprotectin (recommended only if inflammatory bowel disease is suspected).

  • Noninflammatory diarrhea, infectious:

This is the most common type of diarrheal disease, and its etiology is often viral (Rotavirus, Norovirus) but may also be caused by bacteria (Vibrio cholerae, enterotoxigenic Escherichia Coli, Clostridium perfringens, Staphylococcus aureus, Bacillus cereus) or less frequently by parasites (Giardia, Cryptosporidium). Physical findings are mostly abdominal discomfort, nausea, and vomiting. PCR or NAAT results are positive, but testing is not usually necessary or recommended.

  • Noninflammatory diarrhea, noninfectious:

Noninfectious, noninflammatory diarrhea usually happens due to dietary intolerance or psychosocial stressors. Physical findings include nausea and abdominal discomfort, but vomiting is not frequent. PCR or NAAT laboratory tests are negative, but specific tests -such as anti-tissue transglutaminase antibody may be positive.

Specific Treatment of Acute Diarrhea

When properly used, antimicrobials are effective for traveler’s diarrhea, shigellosis, C. difficile, campylobacteriosis, and protozoal infections. In the cases of suspected Shiga toxin–producing E. coli, antibiotic use should be avoided since it may increase the risk of hemolytic uremic syndrome. (17)

The choice of an antimicrobial should be determined according to the susceptibility patterns of pathogens in the patient’s geographical region.

Cause Preferred medication Alternative medications Comments
Cholera Doxycycline, 300 mg once Erythromycin, 250 mg four times per day for three days Selection of an antimicrobial should be based on sensitivity patterns of strains of Vibrio Cholerae recently isolated in the area.
Tetracycline, 500 mg four times a day for three days
Shigella dysentery Ciprofloxacin, 500 mg two times per day for three days Pivmecillinam, 400 mg, four times a day for five days Selection of an antimicrobial should be based on sensitivity patterns of strains of Shigella recently isolated in the area.
Amoebiasis Metronidazole, 750 mg three times per day for five days Treatment should be prolonged for ten days in case of severe disease
Giardiasis Metronidazole, 250 mg three times per day for five days

Clinical guidelines obtained from the World Health Organization (WHO). (15)

Management algorithm in adults with acute diarrhea:

  1. Perform an initial assessment of the patient.
  2. If signs of dehydration are present, correct electrolyte and fluid balance using oral rehydration solution (ORS) or intravenous fluids accordingly.
  3. If no signs of dehydration are present, use home-based fluids or ORS solution to prevent it. ORS can be doubled by mixing 1 liter of potable water, 1/2 teaspoon of salt, and 6 teaspoons of sugar. (16)
  4. Get additional information for further management:
    1. Epidemiological information: food, antibiotics, travel, outbreaks, season, comorbidities, sexual activity, etc.
    2. Clinical signs and symptoms: stool characteristics, abdominal pain, dysentery, vomiting, etc.
  5. Manage symptoms (in the case of non-dysenteric traveler’s diarrhea, consider bismuth subsalicylate or loperamide if needed).
  6. If the diagnosis remains unclear, send a fecal sample for analysis.
  7. Consider antimicrobial treatment for specific pathogens.
  8. Notify the public health authorities in case of Shiga toxin–producing  coli., giardiasis, salmonellosis, cholera, cryptosporidiosis, and shigellosis.

Prevention of Acute Diarrhea

Prevention of acute diarrheal disease is promoted through good hygiene, adequate hand washing, access to clean water, safe food preparation, and vaccinations. (1, 16)

Effective and safe vaccines are approved for cholera, rotavirus, and typhoid fever. Vaccines for enterotoxigenic Escherichia coli, Campylobacter, and Shigella infections are currently under investigation. (13, 16)


The author does not report any conflict of interest.


This information is for educational purposes and is not intended to treat disease or supplant professional medical judgment. Physicians should follow local policy regarding the diagnosis and management of medical conditions.

See Also

Acute Otitis

Acute Upper Respiratory Tract Infections

Acute Abdomen

Approach to the Patient With Acute Vestibular Symptoms

Nephrolithiasis in Adults

Distal Radius Fractures in Adults


  1. Farthing, Michael, Salam, Mohammed A., Lindberg, Greger, Dite, Petr, Khalif, Igor, Salazar-Lindo, Eduardo, et al. Acute Diarrhea in Adults and Children: A Global Perspective. Journal of Clinical Gastroenterology. January 2013. Available from:
  2. World Health Organization. Fact Sheets: Diarrhoeal disease. 2017. Available from:
  3. Meisenheimer ES, Epstein C, Thiel D. Acute diarrhea in adults. American Family Physician. 2022. Available from:
  4. DuPont HL. Acute infectious diarrhea in immunocompetent adults: Nejm. New England Journal of Medicine. 2014. Available from:
  5. Scallan E, Griffin PM, Angulo FJ, Tauxe RV, Hoekstra RM. Foodborne illness acquired in the United States-unspecified agents. Emerg Infect Dis. 2011. Available from:
  6. Laurent Beaugerie, Harry Sokol. Diarrhées infectieuses aiguës de l’adulte : épidémiologie et prise en charge. Acute infectious diarrhea in adults: Epidemiology and management. La Presse Médicale. 2013. Available from:
  7. Jaime Aranda-Michel, Ralph A Giannella. Acute diarrhea: a practical review. The American Journal of Medicine. 1999. Available from:
  8. Belliot G, Lopman BA, Ambert-Balay K, Pothier P. The burden of norovirus gastroenteritis: an important foodborne and healthcare-related infection. Clin Microbiol Infect. 2014. Available from:
  9. Joseph S. Bresee, Ruthanne Marcus, Richard A. Venezia, William E. Keene, Dale Morse, Mark Thanassi, et al,: The Etiology of Severe Acute Gastroenteritis Among Adults Visiting Emergency Departments in the United States. The Journal of Infectious Diseases. 2012. Available from:
  10. Xiao H-L, Ma S-X, Qi H-Y, Li X, Wang Y, Yin C-H. A scoring system for assessing the severity of acute diarrhea of adult patients. World journal of emergency medicine. U.S. National Library of Medicine; 2016. Available from:
  11. Casburn-Jones AC, Farthing MJ. Management of infectious diarrhoea. Gut. 2004. Available from:
  12. Guerrant RL, Van Gilder T, Steiner TS, Thielman NM, Slutsker L, Tauxe RV, et al.; Infectious Diseases Society of America. Practice guidelines for the management of infectious diarrhea. Clin Infect Dis. 2001. Available from:
  13. Shane AL, Mody RK, Crump JA, Tarr PI, Steiner TS, Kotloff K, et al. 2017 Infectious Diseases Society of America Clinical Practice Guidelines for the diagnosis and management of infectious diarrhea. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. U.S. National Library of Medicine; 2017. Available from:
  14. McMahan ZH, DuPont HL. Review article: the history of acute infectious diarrhoea management—from poorly focused empiricism to fluid therapy and modern pharmacotherapy. Aliment Pharmacol Ther. 2007. Available from:
  15. World Health Organization. The Treatment of diarrhoea: a manual for physicians and other senior health workers. 4th rev. 2005. Available from:
  16. Barr W, Smith A. Acute diarrhea in adults. American Family Physician. 2014. Available from:
  17. Wong CS, Jelacic S, Habeeb RL, Watkins SL, Tarr PI. The risk of the hemolytic-uremic syndrome after antibiotic treatment of Escherichia coli O157:H7 infections. Nejm. New England Journal of Medicine. 2000. Available from:

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