The first step for managing any patient with diarrhea is to determine the severity of dehydration according to the estimated volume loss and the symptoms and signs noted on physical examination. The following discussion applies only to adults with acute diarrhea; children and the elderly are managed differently.
Oral rehydration is recommended to alleviate mild dehydration, which often causes minimal to no signs or symptoms. Although not always clinically apparent, volume deficiency is still present to a small degree because of fluid loss through diarrhea. Rehydration should be accomplished with oral rehydration salts mixed with water to ensure that electrolytes are also replenished; Pedialyte is an acceptable alternative to oral rehydration salts. The patient should sip these gradually, consuming 1.5 to 2 times the estimated volume of stool lost per day.10 Sports drinks such as Gatorade and Powerade are designed to replace electrolytes lost in sweat during workout and are not adequate to replace fluid lost during acute diarrhea. Fruit juices and chicken broth are also inadequate sources of rehydration.
Moderate to severe dehydration, hypovolemic shock, or mild dehydration with the inability to tolerate oral rehydration should be managed with intravenous lactated Ringer solution. Lactated Ringer solution is preferred to normal saline because it can quickly correct the potassium deficit that develops during diarrhea. At least half of the estimated volume deficit should be replaced in the first 4 hours after presentation and the rest in 24 hours, with oral rehydration added whenever possible to make up for ongoing losses. For patients with ongoing bouts of heavy diarrhea, fluids should be continued to match the amount of loss, in addition to oral potassium supplements.10
The further treatment of acute infectious diarrhea should depend on the suspected etiology, with viral illness requiring symptomatic management and bacterial illness requiring antibiotics in certain instances. Typically, diarrhea with a viral cause is self-limited, and therapy is focused on rehydration and symptomatic relief. The most commonly used agents to relieve symptoms include loperamide and bismuth subsalicylate.11 Loperamide is an antimotility agent that antagonizes the opioid receptors of smooth muscle in the gastrointestinal tract to decrease peristalsis and increase gut transit time; it also has an antisecretory function. Bismuth subsalicylate functions as both an antimicrobial and an antisecretory agent. Studies have shown that loperamide is more effective and relieves symptoms faster than does bismuth subsalicylate.31
According to the IDSA practice guidelines, bacterial gastroenteritis may be treated empirically or specifically with antibiotics, depending on the etiology. If the patient has been traveling internationally and the symptoms consist of watery, nonbloody stool in an afebrile patient, the illness may be classified as traveler’s diarrhea. Traveler’s diarrhea is most often caused by ETEC or EAEC32 but may also be caused by a number of noninvasive bacterial or viral pathogens. In mild cases, defined as the passage of one to three loose stools per day that does not limit activity, symptomatic therapy with loperamide or bismuth subsalicylate is sufficient, without the need for antibiotics; ondansetron and promethazine are other agents that may be administered for travelers who will be traveling for long periods of time with little access to care.32 For more severe cases, empirical antibiotic therapy is indicated and can limit the duration of illness to as little as 1.5 days if taken at the first sign of illness.8 Fluoroquinolones for adults and trimethoprim-sulfamethoxazole for children cover most of the bacteria causing traveler’s diarrhea, with the exception of bacteria in certain areas of Asia.9,33 For adult visitors to South and Southeast Asia, macrolides should be administered instead. In these areas, Campylobacter jejuni is another common cause of diarrhea and is often fluoroquinolone-resistant.32 Symptomatic therapy may be used concurrently with antibiotics in more severe cases to limit the severity and duration of illness.8
For patients traveling internationally with limited access to medical care, it is often impractical to visit a doctor after an uncomplicated diarrhea develops; in these instances, self-therapy with symptomatic agents and empirical antibiotics brought in traveler kits has been shown to be effective.32,34 Of course, travelers should be educated about the presentation of traveler’s diarrhea and the importance of rehydration and electrolyte repletion in such scenarios.32 Emphasis should be placed on using the provided drugs only if the stool is not bloody and the patient is afebrile. Patients should also be instructed to take sanitary precautions, such as frequently washing their hands and avoiding street food while traveling, to lower the likelihood of acquiring a diarrheal illness.32
In invasive cases of bacterial diarrhea, specific antibiotic therapy based on culture results is safer to use than empirical therapy because it reduces the risk for the development of multidrug resistance of the offending organism or gut colonization by other multidrug-resistant strains; for example, the use of vancomycin to treat C. difficile colitis increases the risk for colonization with vancomycin-resistant enterococci. For these reasons, the antimicrobial spectrum should be narrowed whenever possible and the duration of antibiotic therapy minimized.11 Specific antibiotics are also indicated for parasitic acute diarrhea.
The following table, adapted from the practice guidelines of the IDSA, provides examples of antibiotics and dosages indicated for acute diarrhea caused by specific pathogens. It should be noted that the dosages listed apply only to immunocompetent adults and should not be the recommended therapy for children and immunocompromised adults. Additional options for antibiotic therapy and the indications for children, the immunocompromised, and patients with comorbidities and severe illness can be found in the IDSA practice guidelines.
Exceptions to antibiotic therapy
Antibiotics are not always indicated for invasive bacterial diarrhea, most notably in cases of nontyphoidal Salmonella gastroenteritis. Nontyphoidal Salmonella gastroenteritis in immunocompetent patients usually causes self-limited diarrhea, and antibiotics do not significantly shorten the course. In addition, antibiotics prolong fecal shedding of this pathogen, increasing the risk for transmission. Antibiotic treatment should be undertaken only in newborns up to 6 months old, individuals older than 50 years of age, and persons with a prosthesis, valvular heart disease, severe atherosclerosis, cancer, or uremia. Infection with EHEC strain O157, also known as STEC, is another exception to antibiotic therapy; data indicate that antibiotic therapy may be associated with an increased risk for HUS,9,33 and a consensus has not been reached regarding any benefit of antibiotic therapy. Yersinia infections are also usually self-limited, and only patients with severe infection or bacteremia require antibiotics.9
Agents to relieve symptoms must be used with caution in cases of invasive diarrhea, and loperamide must be avoided completely when fever or bloody diarrhea is present because of the risk for fulminant colitis in patients with severe bacterial gastroenteritis. In suspected cases of EHEC or STEC, antimotility agents must be avoided because of the increased risk for HUS.9
Sharmistha Saha, MD, is a pediatric resident at the Baylor College of Medicine in Houston, Paul Hobbs, MD, is a physician at Barnes Jewish Hospital, Washington University in St. Louis, and Maura Holcomb, MD, is a dermatologist at the Memorial Hermann Sugar Land Hospital in Texas.
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- Manatsathit S, Dupont HL, Farthing M, et al; Working Party of the Program Committ of the Bangkok World Congress of Gastroenterology 2002. Guideline for the management of acute diarrhea in adults. J Gastroenterol Hepatol. 2002;17 Suppl:S54-S71.
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- Adachi JA, Jiang ZD, Mathewson JJ, et al. Enteroaggregative Escherichia coli as a major etiologic agent in traveler’s diarrhea in 3 regions of the world. Clin Infect Dis. 2001;32:1706-1709. doi: 10.1086/320756
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