INTRODUCTION

Section 2 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Background

Gastroenteritis is a nonspecific term for various pathologic states of the gastrointestinal tract. The primary manifestation is diarrhea, but it may be accompanied by nausea, vomiting, and abdominal pain. A universal definition of diarrhea does not exist, although patients seem to have no difficulty defining their own situation. Although most definitions center on the frequency, consistency, and water content of stools, the author prefers defining diarrhea as stools that take the shape of their container.

The severity of illness may vary from mild and inconvenient to severe and life threatening. Appropriate management requires extensive history and assessment and appropriate, general supportive treatment that is often etiology specific. Diarrhea associated with nausea and vomiting is referred to as gastroenteritis.

Diarrhea is one of the most common reasons patients seek medical care. In the developed world, it is the most common reason for missing work, while in the developing world, it is a leading cause of death. In developing countries, diarrhea is a seasonal scourge usually worsened by natural phenomena, as evidenced by monsoon floods in Bangladesh in 1998. An estimated 100 million cases of acute diarrhea occur every year in the United States. Of these patients, 90% do not seek medical attention, and 1-2% require admission. Diarrheal diseases can quickly reach epidemic proportions, rapidly overwhelming public health systems in even the most advanced societies.

Pathophysiology

Infectious agents usually cause acute gastroenteritis. These agents cause diarrhea by adherence, mucosal invasion, enterotoxin production, and/or cytotoxin production.

These mechanisms result in increased fluid secretion and/or decreased absorption. This produces an increased luminal fluid content that cannot be adequately reabsorbed, leading to dehydration and the loss of electrolytes and nutrients.

Diarrheal illnesses may be classified as follows:

• Osmotic, due to an increase in the osmotic load presented to the intestinal lumen, either through excessive intake or diminished absorption
• Inflammatory (or mucosal), when the mucosal lining of the intestine is inflamed
• Secretory, when increased secretory activity occurs
• Motile, caused by intestinal motility disorders

The small intestine is the prime absorptive surface. The colon then absorbs additional fluid, transforming a relatively liquid fecal stream in the cecum to well-formed solid stool in the rectosigmoid.

Disorders of the small intestine result in increased amounts of diarrheal fluid with a concomitantly greater loss of electrolytes and nutrients.

Microorganisms may produce toxins that facilitate infection. Enterotoxins are generated by bacteria (ie, enterotoxigenic Escherichia coli, Vibrio cholera) that act directly on secretory mechanisms and produce typical, copious watery (rice water) diarrhea. No mucosal invasion occurs. The small intestines are primarily affected, and elevation of the adenosine monophosphate (AMP) levels is the common mechanism.

Cytotoxin production by bacteria (ie, Shigella dysenteriae, Vibrio parahaemolyticus, Clostridium difficile, enterohemorrhagic E coli) results in mucosal cell destruction that leads to bloody stools with inflammatory cells. A resulting decreased absorptive ability occurs.

Enterocyte invasion is the preferred method by which microbes such as Shigella and Campylobacter organisms and enteroinvasive E coli cause destruction and inflammatory diarrhea. Similarly, Salmonella and Yersinia species also invade cells but do not cause cell death. Hence, dysentery does not usually occur. However, these bacteria invade the bloodstream across the lamina propria and cause enteric fever such as typhoid.

Diarrheal illness occurs when microbial virulence overwhelms normal host defenses. A large inoculum may overwhelm the host capacity to mount an effective defense. Normally, more than 100,000 E coli are required to cause disease, while only 10 Entamoeba or Giardia cysts may suffice to do the same. Some organisms (eg, V cholera, enterotoxigenic E coli) produce proteins that aid their adherence to the intestinal wall, thereby displacing the normal flora and colonizing the intestinal lumen.

In addition to the ingestion of pathogenic organisms or toxins, other intrinsic factors can lead to infection. An alteration of normal bowel flora can create a biologic void that is filled by pathogens. This occurs most commonly after antibiotic administration, but infants are also at risk prior to colonization with normal bowel flora.

The normally acidic pH of the stomach and colon is an effective antimicrobial defense. In achlorhydric states (ie, caused by antacids, histamine-2 [H2] blockers, gastric surgery, decreased colonic anaerobic flora), this defense is weakened.

Hypomotility states may result in colonization by pathogens, especially in the proximal small bowel, where motility is the major mechanism in the removal of organisms. Hypomotility may be induced by antiperistaltic agents (eg, opiates, diphenoxylate and atropine [Lomotil], loperamide) or anomalous anatomy (eg, fistulae, diverticula, antiperistaltic afferent loops) or is inherent in disorders such as diabetes mellitus or scleroderma.

The immunocompromised host is more susceptible to infection, as evidenced by the wide spectrum of diarrheal pathogens in patients with AIDS.

The exact mechanism of vomiting in acute diarrheal illness is not known, although serotonin release has been postulated as a cause, stimulating visceral afferent input to the chemoreceptor trigger zone in the lower brainstem. Preformed neurotoxins produced by Staphylococcus aureus and Bacillus cereus, when ingested, can cause severe vomiting.

Frequency

United States

Frequency is difficult to determine because of underreporting, especially of mild illness, resulting in wide variations of estimated numbers of cases, hospitalizations, and deaths. As many as 90 million cases occur per year with several million healthcare visits and thousands of hospitalizations. According to the Centers for Disease Control and Prevention (CDC), 3.5 million cases of acute diarrhea from rotavirus alone and at least 90,000 cases of food poisoning occur yearly. It is estimated that the norovirus is responsible for more than 70% of GI illnesses in the USA, probably more than 23 million cases a year and up to 93% of outbreaks. In Great Britain, it has been known as winter vomiting disease. Whether the increased incidence is real or simply a result of increased awareness, surveillance, and reporting is unclear.

The following are examples of sporadic common source outbreaks:

• Gastroenteritis associated with V parahaemolyticus infection from Gulf Coast oysters has been reported.
• Salmonella gastroenteritis from reptilian pets has been reported.
• A religious cult in Oregon intentionally contaminated salad with Salmonella typhimurium, which resulted in 751 victims who developed acute gastroenteritis.
• In July 1998, more than 60 persons in Wyoming were infected with E coli O157:H7 from a contaminated water supply.
• In 1993, E coli O157:H7–contaminated fast-food hamburger meat in the Pacific Northwest infected 500 persons, 4 of whom died.
• From 1981-1994, 333 cases of Vibrio vulnificus infection associated with raw oyster consumption were reported in Florida. Two persons died from gastroenteritis, and 50 persons died from septicemia.
• In January 1995, 322 cases of Norwalk virus (calicivirus) infection–associated acute gastroenteritis resulted from the consumption of raw oysters in Florida.
• In October 1996, 629 children and staff members at one elementary school in Florida were infected in a point-source outbreak of a Norwalk-like agent (calicivirus).
• In July 1995, 77 cases of cryptosporidiosis at a day camp in Florida were reported, most likely secondary to contamination involving a water hose.
• In April 1994, 96 cases of Campylobacter infection were reported in Florida. The common source was ingested, contaminated commercial ice cubes.
• In 1996, Norwalk virus–associated gastroenteritis resulted from the ingestion of raw oysters in Louisiana.
• From May 1996 to June 1996, E coli O157:H7 infections secondary to consumption of mesclun lettuce from a single producer were reported in multiple states (first identified in Connecticut and Illinois).
• In August and September of 1999, E coli O157:H7 infections secondary to contaminated well water at the Washington County Fair (New York) were reported.
• Norwalk virus is the leading cause of viral gastroenteritis in the United States.
• From January 1, 2002, to December 2, 2002, norovirus was attributed to 9 of the 21 outbreaks of acute gastroenteritis on cruise ships reported to the CDC's Vessel Sanitation Program in this period. Noroviruses cause approximately 23 million cases of acute gastroenteritis each year and are the leading cause of gastroenteritis outbreaks.
• Norovirus outbreaks have been reported in various locations, including casinos, airplanes, schools, hospitals, nursing homes, and cruise ships.
• In 2005, E coli O157:H7 infections secondary to contaminated animals were reported at Florida fairs.
• Between January 1996 and November 2000, 348 outbreaks of norovirus (also known as Norwalk virus or Norwalk-like virus) were reported to the CDC. 
• Amongst all cruise ship voyages under the auspices of the CDC's Vessel Sanitation Program (VSP), 11 reported outbreaks have been confirmed secondary to norovirus on cruise ships in 2007 through September and an additional 7 suspected. The CDC posts outbreaks as occurring on voyages from 3-21 days, on ships carrying 100 or more passengers in which 3% or more of passengers or crew reported symptoms of diarrheal disease to the ships medical staff during the voyage, and are gastrointestinal illness outbreaks of public health significance.
• While cruise ship outbreaks get the most publicity, outbreaks have also occurred at casinos, nursing homes, hospitals, amusement parks, camps, military facilities, and schools.

International

Three to five billion cases of acute diarrhea occur yearly, and it is the leading cause of death in many underdeveloped countries. Approximately 30-50% of visitors to developing countries develop, and perhaps return with, diarrhea. In 2001 and 2002, outbreaks of gastroenteritis caused by norovirus were reported in diverse locations such as the American Midwest; Boston; Northern Europe; St. Petersburg, Russia; Canada; and Alaska.

Mortality/Morbidity

• Estimates for mortality and morbidity widely vary. In the United States, 210,000 pediatric hospitalizations occur yearly, with as many as 10,000 deaths.
• Internationally, the mortality rate is 5-10 million deaths each year.

Age

• Pediatric gastroenteritis is discussed in Pediatrics, Gastroenteritis.
• Gastroenteritis may occur at any age. Morbidity and mortality are much higher in the very young and the very old.

CLINICAL

Section 3 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

History

A well-taken history, considering important epidemiologic factors, can help to identify not only the cause of diarrhea but also the patient at risk for complications. History in infectious cases and food poisoning varies depending upon the agent with variation in the onset; the frequency and nature of the stools; and the presence or absence of blood and mucus, vomiting, cramps, and fever. The history should also identify risk factors for unusual causes of acute gastroenteritis and possible reasons to suspect noninfectious etiologies. Indications of dehydration or sepsis should also be sought. As an example, norovirus is usually diagnosed by history. The incubation period for the norovirus is between 12 and 48 hours. Some of the early symptoms include nausea, a sudden onset of vomiting, moderate diarrhea, headache, fever (~50%), chills, and myalgia and will last 12-60 hours. The clinical factors suggestive of norovirus include the patient's presentation and the sudden onset of symptoms, with uncontrolled vomiting being a classic sign. Usually, more vomiting than diarrhea occurs. The natural course of this illness usually provides resolution within 36 hours. 

• Duration of illness
• • Duration and rapidity of symptom onset are important in determining the incubation period and possible infecting organism and in directing further care.
  • Diarrhea that lasts longer than a month requires consideration of a different spectrum of etiologic factors than diarrhea that lasts less than 1-2 weeks.
• Fever: The presence of fever (with or without chills) generally suggests that an invasive organism is the cause of diarrhea, although many extraintestinal illnesses can present with both fever and diarrhea, especially in children.
• Vomiting
• • Vomiting, a symptom common to a host of illnesses, implies proximal bowel involvement, especially with preformed neurotoxin, as elaborated by S aureus and B cereus.
  • Vomiting is a leading symptom of intestinal obstruction, usually coupled with distention; however, distention may not be significant if the obstructing lesion is very proximal. Vomiting without diarrhea must always prompt a search for noninfectious causes and cannot be referred to as gastroenteritis.
• Pain
• • The location and character of pain may be indicative of the area of infection because colonic involvement is usually associated with tenesmus and pain in either of the lower quadrants or the lower back, whereas jejunoileal infection may result in periumbilical pain.
  • Cramps may be caused by an electrolyte imbalance.
  • Pain, especially in patients older than 50 years, should raise the suspicion of an ischemic process.
• Stools
• • Ask about frequency, nature (amount, color, watery, semisolid, odor), and presence of blood and/or mucus.
  • Large volumes of stool are usually associated with enteric infection, whereas colonic infection results in many small stools.
  • The presence of blood indicates colonic ulceration (bacterial infection, inflammatory disease, ischemia).
  • White bulky feces that float (high fat content) are due to a small bowel pathology that leads to malabsorption.
  • Copious (rice water) diarrhea is a hallmark of cholera.
• Extraintestinal causes
• • A history of other nonintestinal illnesses that can lead to diarrhea may be obtained. Vomiting and/or diarrhea may be a manifestation of that illness or a result of its treatment. Obtaining a history of recent surgery or radiation, food or drug allergies, and endocrine or gastrointestinal disorders is extremely important. The patient should always be questioned regarding prior episodes.
  • Malaria, Whipple disease, irritable bowel, incomplete bowel obstruction, inflammatory disease, nutritional disease, and carcinoid and malabsorption syndromes can result in diarrhea.
  • Drugs such as colchicine, quinidine, antimicrobials, cancer chemotherapeutic agents, and magnesium-containing antacids frequently cause diarrhea.
• Dehydration
• • Orthostasis, lightheadedness, diminished urine formation, and a change in mentation herald marked dehydration and electrolyte loss, requiring aggressive treatment.
  • These symptoms are particularly important in elderly patients, a group that is most at risk from diarrhea.
• Epidemiologic factors
• • A number of historical questions may provide clues to the etiology of the illness, including foreign travel, recent camping, recent antibiotic use, daycare attendance, and/or ingestion of raw, possibly spoiled, or new marine products, as well as similar illnesses in family, friends, or contacts.
  • An epidemiologic factor may be travel to developing countries where bacterial or parasitic agents can cause infection or to campgrounds in developed regions, where agents such as Giardia lamblia, Aeromonas, and Cryptosporidium can contaminate untreated water.
  • Enterotoxigenic E coli is the most frequent cause of traveler's diarrhea. Symptoms usually begin within days of arrival in the region and can last from 5 days to 2 weeks.
  • Vibrio species are more common in Asia, although epidemics have occurred in Central America within the last 10 years.
  • As many as 12% of diarrheal illness cases may be caused by rotavirus in travelers to Asia, Africa, and South America.
  • Men who are homosexual are more prone to infection by usual pathogens via the fecal-oral route (ie, Shigella, Campylobacter jejuni, Salmonella, protozoalike Entamoeba). Anal receptive intercourse may result in the direct inoculation of Neisseria gonorrhoeae, Chlamydia trachomatis, Treponema pallidum, and herpes simplex virus. Severely immunocompromised states (CD4 cell count <200) increase the risk of infection by agents such as Mycobacterium avium complex, microsporidia, cytomegalovirus (CMV), and Isospora belli.
  • Recent use of antimicrobial drugs increases the risk of C difficile infection.
  • A common source outbreak from contaminated water and food may cause gastroenteritis either by infection (C jejuni, G lamblia) or by ingestion of a preformed toxin (E coli O157:H7, scombroid, ciguatera).
  • Infections via the fecal-oral route are prevalent in children who attend daycare centers. Rotavirus has an infection rate of nearly 100% in exposed children younger than 2 years. Other family members are also at risk for infection.

Physical

A thorough physical examination is essential to assess the general state of hydration and nutrition and to exclude extraintestinal causes of diarrhea. Often, the cause of diarrhea cannot be determined based on the physical findings present, which may be scarce.

• The most important element of the physical examination is the assessment of the patient's hydration status. (Dehydration in children, for example, is classified according to the degree of hydration/percentage deficit as <3%, none; 3-6%, mild; 6-9%, moderate; and >10%, severe.) Additionally, signs of bacteremia or sepsis should be sought. Patients with chronic diarrhea may need an evaluation of their nutritional status.
• A rectal examination should be performed, involving checking for blood and mucus. Rectal examination may reveal abscesses, fistulae, and fissures, which may indicate inflammatory bowel disease. A partially obstructing tumor or a fecal impaction may be discovered as a cause of diarrhea. Finally, the stool can be examined for the presence of blood and pus.
• Hydration and nutritional status
• • Diminished skin turgor, weight loss, resting hypotension and tachycardia, dry mucus membranes, decreased frequency of urination, changes in mental status, and orthostasis can be used to gauge dehydration.
  • In children, the absence of tears, poor capillary refill, sunken eyes, depressed fontanelles, increased axillary skin folds, and dry diapers all may reflect a dehydrated state.
  • Muscle wasting and signs of neural dysfunction due to nutritional depletion may be observed in patients with chronic diarrhea.
• Abdominal examination
• • A careful abdominal examination is necessary to exclude causes of diarrhea that may require surgical intervention, such as pelvic abscesses close to the rectosigmoid that are causing tenesmus.
  • The examiner should look for signs of an acute abdomen, listening for bowel sounds, determining the location of any tenderness, and palpating for masses or organomegaly.
  • Appendicitis in children may manifest as diarrhea.

Causes

• Viral (50-70%)
• • Norovirus
  • • This is the leading cause of viral gastroenteritis in the United States. Noroviruses (formerly known as Norwalk virus in the United States and as small round structured virus [SRSV] in the United Kingdom), along with the sapoviruses (formerly known as Sapporo-like viruses), are members of the Caliciviridae family of viruses. The norovirus is a small, 26-40 nm, nonenveloped, single-stranded RNA virus classified as a Calicivirus. Sapoviruses, a cause of gastroenteritis, predominantly in children, are also in the Caliciviridae family. Five norovirus genogroups have been identified: GI, GII, GIII, GIV, and GV; 27 clusters (genotypes) have also been identified. In 2006, the land-based experience was slightly busier than usual. The dominating strain was GII-4 (Bristol).
    • It is a highly infectious virus—with as few as 10-100 particles necessary for transmission—and is quite resistant to quaternary ammonia compounds, alcohol, detergent-based compounds, freezing, and heat (to 60^oC). It is a very difficult virus to culture and measure; thus, studies on norovirus are limited, with researchers using a "surrogate," nonenveloped virus, Feline Calicivirus (FCV), to assess the efficacy of disinfectants and other mitigation strategies. Recently, some researchers have questioned the use of FCV as a surrogate since FCV is a respiratory virus and norovirus is a GI virus and likely is more resilient than FCV due to the need for norovirus to survive in the hostile environment of the gut. Therefore, the results of testing performed to validate the efficacy of disinfectants and hand sanitizers possibly overestimate the actual effectiveness of these products on human norovirus.
  • • Various modes of transmission exist including fecal-oral transmission (predominant), person to person, fecal contamination of food and/or water, fomite transmission, and even potential airborne spread when in close proximity of someone vomiting
    • Between January 1996 and November 2000, 348 outbreaks of norovirus were reported to the CDC. Out of these, 54% patients were contaminated by food, 17% by person to person, 4% by water, and 25% by unidentified sources. Most of the food sources responsible were identified as oysters, salads, salad dressing, sandwiches, deli meats, cake and frosting, raspberries, drinking water, and ice. Shellfish have been implicated in some outbreaks, but it is not a frequent source on cruise ships, where the predominant mode of infection is believed to be fecal-oral and person to person from individuals who come onto the ships ill and do not report the illness or quarantine themselves in their cabins. The same study reveals that 39% contracted the disease in restaurants, 30% in nursing homes, 12% at school, 10% on vacation, and 9% remain unidentified.  
    • The incubation period for the norovirus is between 12 and 48 hours. Some of the early symptoms include nausea, a sudden onset of vomiting, moderate diarrhea, headache, fever (~50%), chills, and myalgia and will last 12-60 hours. The clinical factors suggestive of norovirus include the patient's presentation and the sudden onset of symptoms, with uncontrolled vomiting being a classic sign. Usually, more vomiting than diarrhea occurs. The natural course of this illness usually provides resolution within 36 hours. Unless the patient is very young, very old, debilitated with severe underlying disease, or immunocompromised, they usually do very well with this self-limited illness, responding to oral rehydration and a rapid return to normal diet once the vomiting has ceased. The only therapy is oral and/or intravenous hydration with occasional need for antiemetics. The usual cautions concerning the use of antiemetics in very young patients apply. Although viral shedding has been reported for up to 2 weeks, the polymerase chain reaction (PCR) testing used to determine this may just be detecting inactivated RNA. 
  • Caliciviruses (Various caliciviruses, other than norovirus, are likely responsible for many outbreaks of previously unidentified viral gastroenteritis.)
  • Rotavirus (This is the leading cause of gastroenteritis in children, but rotavirus can also be found in adults. Rotavirus may cause severe dehydration.)
  • Adenovirus
  • Parvovirus
  • Astrovirus
  • Coronavirus
  • Pestivirus
  • Torovirus
• Bacterial (15-20%)
• • Shigella
  • Salmonella
  • C jejuni
  • Yersinia enterocolitica
  • E coli - Enterohemorrhagic O157:H7, enterotoxigenic, enteroadherent, enteroinvasive
  • V cholera
  • Aeromonas
  • B cereus
  • C difficile
  • Clostridium perfringens
  • Listeria
  • M avium-intracellulare (MAI), immunocompromised
  • Providencia
  • V parahaemolyticus
  • V vulnificus
• Parasitic (10-15%)
• • Giardia
  • Amebiasis
  • Cryptosporidium
  • Cyclospora
• Food-borne toxigenic diarrhea  
• • Preformed toxin - S aureus, B cereus
  • Postcolonization - V cholera, C perfringens, enterotoxigenic E coli, Aeromonas
• Shellfish poisoning and poisoning from other marine animals
• • Paralytic shellfish poisoning (PSP) - Saxitoxin
  • Neurologic shellfish poisoning (NSP) - Brevetoxin
  • Diarrheal shellfish poisoning (DSP) - Okadaic acid
  • Amnesic shellfish poisoning - Domoic acid
  • Ciguatera (ciguatoxins)
  • Scombroid (conversion of histidine to histamine)
• Drug-associated diarrhea
• • Antibiotics, due to alteration of normal flora
  • Laxatives, including magnesium-containing antacids
  • Colchicine
  • Quinidine
  • Cholinergics
  • Sorbitol
• Pseudomembranous colitis
• • Overgrowth of C difficile
  • Positive C difficile assay findings
• Other causes
• • Unknown agents, especially in developing countries
  • Ischemic colitis
  • Ulcerative colitis
  • Crohn disease
  • Carcinoid tumor or vasoactive intestinal peptide tumor (VIPoma)
  • AIDS
  • Dumping or short bowel syndrome
  • Radiation or chemotherapy

DIFFERENTIALS

Section 4 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Other Problems to be Considered

Various infectious etiologies
Pseudomembranous colitis
Food-borne toxigenic diarrhea
Toxins
Hormonal (vasoactive intestinal peptides)
Drugs (ie, sorbitol, cholinergics, caffeine)
Surgery
Radiation colitis
Carcinoid
Pediatrics - Adrenogenital/cystic fibrosis

WORKUP

Section 5 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Lab Studies

• Determination of laboratory tests: The patient's evaluation should be based on the clinical assessment and the need to do the following:
• • Further evaluate the seriousness of the condition (degree of dehydration and electrolyte derangement).
  • Determine a specific etiologic agent.
  • Evaluate the patient for noninfectious etiologies.
  • Patients who require further workup include those who appear seriously ill or dehydrated; those who have high fevers, bloody stools, severe abdominal pain, or persistent diarrhea; and those who are immunocompromised or whose condition is suspected of having an epidemic diarrheal etiology.
  • History, epidemiologic considerations, and the physical examination should be the primary guides in determining whether any further diagnostic evaluation is necessary, followed by microscopic examination of the stool.
• Stool studies and culture
• • The presence of blood or leukocytes in stool is a strong indicator of inflammatory diarrhea.
  • Stool studies can be performed efficiently and inexpensively by using a Wright stain or methylene blue and directly observing for leukocytes and performing an occult blood test.
  • Fecal leukocytes are present in 80-90% of all patients with Salmonella or Shigella infections but are less common with other infecting organisms such as Campylobacter and Yersinia. They may also be present in ulcerative colitis and Crohn disease but are usually absent in viral infections, Giardia infection, enterogenic E coli infection, and toxigenic bacterial food poisoning.
  • A stool culture is not necessary or cost-effective in all cases of diarrhea unless a bacterial cause is suspected.
  • Fever, bloody stools, leukocytes in stool, pain resembling that associated with appendicitis (Yersinia), and diarrheal illness associated with partially cooked hamburger (cytotoxigenic E coli O157:H7) are all indications for culture.
  • Frequently, stool cultures are obtained inappropriately in the United States. Consider whether obtaining a culture would change the therapy.
  • Specific indications for stool cultures include bloody stools, stools that test positive for occult blood or leukocytes, prolonged course of diarrhea that has not been treated with antibiotics, immunocompromised host, or for epidemiologic purposes, such as cases involving food handlers.
  • Routine stool cultures identify only Campylobacter, Shigella, Salmonella, Aeromonas, and Yersinia species.
  • Testing for other pathogens, such as Vibrio species, enterohemorrhagic E coli O157:H7, and other Shigatoxin-producing bacteria require special media. The laboratory should be informed regarding appropriate media for suspected organisms (eg, MacConkey sorbitol agar for E coli O157:H7). Additionally, the laboratory may need to perform specialized testing to specifically identify the organism.
  • Studies of selected centers have shown that only 2% of stool culture results are positive as routinely obtained. The cost per positive stool culture result has been estimated to be at least $900-1200.
  • Similarly, if parasitic illness is in the differential or if the patient has recently traveled to an endemic region or has chronic diarrhea, the stool should be examined for parasites or their ova with the caveat that several samples may be required to make the diagnosis. Ova and parasite studies are indicated for patients who are immunocompromised, who have a persistent or prolonged course, or whose conditions are unresponsive to antibiotics.
  • Travel to endemic regions followed by chronic diarrhea without signs of acute bacterial diarrhea should prompt a search for a parasitic etiology.
  • Entamoeba histolytica can result in bloody stools, but a smear reveals a lack of leukocytes due to exotoxin produced by the parasite that lyses the cells.
• Routine laboratory tests
• • Routine laboratory tests (CBC, electrolytes, renal function) may not be helpful or indicated in making a diagnosis. These tests may be useful as indicators of severity of disease, especially in elderly or very young patients, although that determination is best made clinically.
  • Electrolytes and BUN tests are indicated in patients with severe diarrhea or dehydration to rule out hyponatremia or hypernatremia. Decreased serum bicarbonate suggests severe dehydration, especially in children. Acidosis secondary to bicarbonate loss in the stools and/or from hypovolemia-induced lactic acidosis may be present. Hypokalemia may also occur.
  • A CBC may be indicated with a prolonged course, severe diarrhea, or toxicity. The WBC count is usually increased in Salmonella infections but normal or low with significant left shift in Shigella infections. The WBC count is otherwise variable. Eosinophilia may be present in parasitic infections.
• Enzyme-linked immunosorbent assay
• • Commercially available immunofluorescent antibody and enzyme immunoassays are also available for Giardia and Cryptosporidium organisms. C difficile toxin assays can be performed when antibiotic-associated diarrhea is suspected.
  • Rotavirus: Enzyme-linked immunosorbent assay (ELISA) is available in less than 2 hours but is not sensitive enough in adults.
  • Giardia: ELISA is more than 90% sensitive in susceptible populations (eg, people who camp or travel to endemic areas). Consider ELISA prior to ova and parasite examination or string test.

Imaging Studies

• An acute abdominal series is indicated only when bowel obstruction, toxic megacolon, or perforation is suspected.

Procedures

• Sigmoidoscopy may be indicated if pseudomembranous colitis or inflammatory bowel disease is suspected. Sigmoidoscopy is useful in obtaining tissue for culture in patients with AIDS who have undiagnosed diarrhea or wasting syndrome.

TREATMENT

Section 6 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Prehospital Care

• Prehospital care is directed toward early and aggressive fluid therapy in patients who are unstable.

Emergency Department Care

• Goals of ED therapy
• • Rehydrate orally or intravenously as needed.
  • Treat symptoms (eg, fever, pain) as indicated.
  • Identify complications.
  • Prevent the spread of infections.
  • Identify public health concerns and treat certain specific cases with specific or empiric antibiotic therapy.
• Rehydration
• • Administration of 1-2 L dextrose 5% in 0.5 isotonic sodium chloride solution with 50 mEq NaHCO₃ and 10-20 mEq KCl over 30-45 minutes may be necessary in patients who are severely dehydrated.
  • Clinical assessment and serum electrolyte concentrations should guide therapy.
  • To give fluids more rapidly, KCl may be given orally or in the second or third liter bag or as a supplemental IV of 20 mEq KCl in 100 mL of isotonic sodium chloride solution over 1 hour.
  • Rehydrate patients until mental status and signs of perfusion and pulse are normal (caution in elderly patients with congestive heart failure [CHF]).
  • For pediatric patients, administer 20 mL/kg of isotonic sodium chloride solution initially for resuscitation. Repeat as necessary and add KCl as indicated.
  • Indications for IV rehydration include severe intractable vomiting, altered consciousness, severe dehydration, ileus, excessive choleralike stools, and time or environment not conducive to oral rehydration therapy (ORT).
  • Solutions for oral rehydration
    • The World Health Organization solution is 90 mEq/L Na⁺, 20 mEq/L K⁺, 80 mEq/L Cl^-, 20 g/L glucose; osmolarity is 310; CHO:Na = 1.2:1; administer 250 mL (approximately 8 oz) every 15 minutes until fluid balance is clinically restored, then 1.5 L of oral fluid per liter of stool.
    • Other products include Naturalyte, Cera Lyte, Rehydralyte, and Pedialyte.
    • Oral rehydration may not decrease the duration or volume of diarrhea.
    • Small amounts of oral fluids may be given repeatedly while the patient is still vomiting.
    • Oral rehydration has been largely responsible for the tremendous decrease in the death rate in underdeveloped countries from infectious diarrhea, including cholera.
    • The glucose/sodium transport mechanism remains intact despite enterotoxigenic illness. Coupled transport is one of several mechanisms of sodium and water absorption in the bowel. It is the direct entry of sodium and water across the cell at the intestinal brush border membrane via the linking (coupling) of 1 organic molecule, such as glucose, to 1 sodium molecule. This is the principle upon which ORT is based. Optimally, therefore, the ratio of carbohydrate to sodium should approach 1:1. Glucose is necessary to stimulate the absorption of water and electrolytes by the small intestines.
  • The solution must be iso-osmolar or hypo-osmolar to avoid an increased osmotic load in the small intestines contributing to an osmotic diarrheal effect, pulling fluid into the lumen.
  • Studies have shown oral and IV rehydration to be equivalent therapies in patients who can tolerate the oral fluid.
  • Although standard glucose-electrolyte solutions achieve and maintain rehydration, they may not reduce stool volume or duration of diarrheal illness, affecting compliance.
  • Newer solutions with complex carbohydrates and short chain polypeptides of cereals and legumes are now available to provide additional organic cotransport molecules with no increase in osmolarity. These appear to offer the advantage of decreased stool volumes and shortened duration of illness.
  • Early age-appropriate refeeding in children (and adults) is important to initiate as soon as rehydration is complete.
    • Early refeeding with complex carbohydrates provides additional cotransport molecules without osmotic penalty and stimulates mucosal repair.
    • Consider rice, wheat, bread, potatoes, and lean meats, especially chicken.
    • Milk can be safely given early. Despite the potential for lactose intolerance, clinical evidence of lactase deficiency is uncommon, and most children can tolerate nonhuman milk without difficulty during acute diarrheal illnesses.
    • What has been learned from studies of early pediatric refeeding probably can be generalized to the adult population. Initiate early feeding with the above dietary recommendations once rehydration has been accomplished and vomiting is controlled.
• Empiric therapy for infectious diarrhea is sometimes indicated. Food-borne toxigenic diarrhea usually requires only supportive treatment, not antibiotics.
  • The duration of traveler's diarrhea (E coli, Shigella) can be shortened by half or more with trimethoprim-sulfamethoxazole (TMP/SMZ) or ciprofloxacin administered for 3 days. Single doses have been used effectively. The duration of treatment may be extended by 2-3 days for moderate-to-severe cases.
  • Generally, fluoroquinolones are the drugs of choice for acute infectious gastroenteritis when used empirically. They do not appear to increase carrier states; however, they are contraindicated in pregnant women and in children.
  • Erythromycin or azithromycin is effective in Campylobacter infections, although erythromycin is not well tolerated in the patient who is vomiting.
  • Metronidazole (oral or parenteral) is effective in mild-to-moderate cases of C difficile diarrhea (in addition to discontinuance of the causative agent). Patients who are severely ill may require orally administered vancomycin, which may require delivery via nasogastric tube or colonoscope.
  • Mild cases of suspected Yersinia infection should be treated with TMP/SMZ or a fluoroquinolone, while patients who are more ill and require admission benefit from IV ceftriaxone.
  • Intestinal salmonellosis in an immunocompetent host does not require antimicrobials because they may prolong fecal shedding of organisms.
  • Metronidazole is effective against parasitic infestations with Giardia or Entamoeba.
• Antiemetics may be useful in the treatment of nausea and vomiting in adults. They are usually not recommended in children.
• Antidiarrheals (antimotility agents)
  • These agents have traditionally been discouraged because of concerns with causing bacteremia; however, they appear to have a role in the symptomatic treatment of mild-to-moderate diarrhea, especially with nonbloody and traveler's diarrhea.
  • The most common agents include bismuth subsalicylate (Pepto-Bismol). For patients older than 14 years, give 2 tablets or 20 mL PO q30min as needed to a maximum of 8 doses and loperamide (Imodium), which is useful as an adjunct to rehydration for symptomatic relief. The American Academy of Pediatrics (AAP) does not recommend this for children.
  • Octreotide (Sandostatin), an analog of somatostatin, may be used subcutaneously and intravenously to control severe secretory diarrhea. It has been approved for this purpose in the treatment of carcinoid tumors and VIPomas. Octreotide is under investigation for other uses, including secretory diarrhea associated with AIDS, short bowel syndrome, dumping syndrome, radiation, and chemotherapy.

Consultations

• A consultation to an infectious diseases specialist may be necessary for patients with chronic diarrhea, patients whose conditions have parasitic etiologies, patients infected with C difficile when vancomycin use is contemplated, patients who relapse, and patients with AIDS who have diarrhea.
• A consultation to a gastroenterologist may also be indicated in the above circumstances and when pseudomembranous colitis, ulcerative colitis, or Crohn disease are in the differential diagnosis.

MEDICATION

Section 7 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

The goals of pharmacotherapy are to reduce morbidity, to prevent complications, and to possibly decrease the duration of illness.

In February 2006, the United States Food and Drug Administration (FDA) approved an oral vaccine for rotavirus (RotaTeq). It is currently the only vaccine approved in the United States for prevention of rotavirus gastroenteritis as of the date of this publication. RotaTeq is administered in a 3-dose series starting between age 6-12 weeks and completed before age 32 weeks.

Drug Category: Antibiotics

Therapy must cover all likely pathogens in the context of the clinical setting.

Drug Category: Antiemetics

All these drugs are indicated in the control of nausea and vomiting. All have been associated with extrapyramidal adverse effects, especially in patients who are acutely ill, dehydrated, or children. They should be used with caution and only in the lowest effective dose. A weak association with Reye syndrome exists, and all may mask the vomiting associated with underlying CNS lesions.

Drug Category: Antidiarrheal agents

These agents are used to decrease the frequency of diarrheal stools and possibly the duration. They should be used with caution in children and in patients with dysentery, as some reports of prolonged illness and development of toxic megacolon exist.

Drug Category: Vaccines

Elicit active immunization to increase resistance to infection. Vaccines consist of microorganisms or cellular components, which act as antigens. Administration of the vaccine stimulates the production of antibodies with specific protective properties.

FOLLOW-UP

Section 8 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Further Inpatient Care

• Continue rehydration and management of electrolytes if ED response is inadequate.
• Manage sepsis in the toxic-appearing patient.
• Evaluate for underlying etiology if the diagnosis is uncertain.
• Manage complications.

Further Outpatient Care

• Rehydrate orally with balanced sodium and glucose solutions.
• Ensure appropriate early oral refeeding.
• Ensure appropriate deterrence and infection control procedures and activities, including notification of common source or close contact exposures, as appropriate.
• Administer antibiotic, antimotility, and antiemetic treatment only as indicated and directed.
• Wash buttocks after each diarrheal stool to avoid effects of stool enzyme on the skin.
• Instruct the patient to return upon experiencing bloody stools, worsening abdominal pain, severe vomiting, and/or concerns regarding dehydration.
• Instruct the patient to seek follow-up care if diarrhea persists longer than 10 days.

In/Out Patient Meds

• Antibiotics
• Antiemetics
• Antimotility agents

Transfer

• Transfer of the unstable patient is inappropriate under Emergency Medical Treatment and Active Labor Act (EMTALA) regulations unless benefits clearly outweigh risks.
• Unless the patient requires admission and has a complicated medical condition that would be better managed in another facility, transfer is neither necessary nor recommended.

Deterrence/Prevention

• The following are factors to consider with breastfeeding:
• • Decreased incidence of rotavirus but does not eliminate this diagnosis
  • Formula supplementation with nonpathogenic bacteria such as Bifidobacterium bifidum
• Take enteric precautions to avoid spread to family members, especially by washing hands before eating and after each stool or diaper change.
• Avoid shellfish served in unregulated environments, in areas with known red tides, or areas of recently reported outbreaks, including Vibrio species and Norwalk virus. Individuals with a history of any liver disease should avoid raw shellfish.
• Wash all produce prior to consumption, especially if imported.
• Avoid cross-contamination of foods during preparation (eg, cutting boards).
• Avoid raw or undercooked eggs or poultry.
• As many as 40% of travelers to high-risk areas (South and Southeast Asia, Africa, and Latin America) contract diarrhea. Dietary precautions, in addition to the above, which will reduce this risk are as follows:
• • Eat steaming hot foods (cooked foods) and drink steaming hot beverages (eg, coffee, tea).
  • Consume acidic foods, such as citrus.
  • Consume dry foods, such as bread and nuts.
  • Drink carbonated beverages.
  • Avoid water, ice, raw fruits without a skin or peel, raw vegetables, unpasteurized milk and dairy products, and foods sold in the streets.
  • Avoid moist foods served at room temperature, leafy green vegetables, and ripened fruit with broken skin.
  • Take the above precautions when aboard the aircraft leaving the high-risk area.
  • Travelers who request prophylaxis can take 2 tablets of Pepto-Bismol with each meal and at bedtime, not exceeding a daily dose of 8 tablets.
  • Although prophylactic antimicrobial therapy generally should be discouraged in the young and healthy traveler, if chemoprophylaxis is requested, a daily single dose of TMP/SMZ or a fluoroquinolone can be provided.
  • Travelers with certain underlying conditions should be encouraged to use prophylactic antibiotics. These include patients with AIDS, inflammatory bowel disease, systemic malignancy, insulin dependency, or achlorhydria and patients taking omeprazole or chronically using H2 antagonists. Sporadic or intermittent H2 antagonist use is not an indication for prophylaxis.
  • Avoid drinking from unfamiliar fresh water sources, such as lakes and rivers.
• Norovirus
• • There are very few ways to entirely eliminate norovirus. Alcohol-based hand sanitizers, used by a number of cruise lines and recommended by hospital-based practices, need a minimum of 30-60 seconds of contact time to be effective and should not be considered a substitute for aggressive handwashing and mechanical drying. In addition, sanitizing the finger tips and under the finger nails with alcohol hand gels is difficult, and this may be another factor in their relative infectiveness in comparison to handwashing with soap and water. Because norovirus is an unencapsulated virus, alcohol-containing products are less effective and require higher concentrations of alcohol. Two popular commercially available products containing 62% and 70% alcohol are not especially effective showing approximately a 2.0 log reduction.
  • Alcohol-based hand gels are relatively ineffective in the disinfection and/or removal of norovirus from the hands. The recent increase in norovirus infection in acute care hospitals may be the result of the