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(See also Allergic and Other Hypersensitivity Disorders: Food Allergy and see Poisoning: Mushroom Poisoning.)
Gastroenteritis is inflammation of the lining of the stomach and small and large intestines. Most cases are infectious, although gastroenteritis may occur after ingestion of drugs and chemical toxins (eg, metals, plant substances). Symptoms include anorexia, nausea, vomiting, diarrhea, and abdominal discomfort. Diagnosis is clinical or by stool culture, although immunoassays are increasingly used. Treatment is symptomatic, although parasitic and some bacterial infections require specific anti-infective therapy.
Gastroenteritis is usually uncomfortable but self-limited. Electrolyte and fluid loss is usually little more than an inconvenience to an otherwise healthy adult but can be grave for people who are very young (see Dehydration and Fluid Therapy in Children: Dehydration in Children), elderly, or debilitated or who have serious concomitant illnesses. Worldwide, an estimated 3 to 6 million children die each year from infectious gastroenteritis.
Etiology
Infectious gastroenteritis may be caused by viruses, bacteria, or parasites. Many specific organisms are discussed further in the Infectious Diseases section.
Viruses:
The viruses most commonly implicated are
Viruses are the most common cause of gastroenteritis in the US. They infect enterocytes in the villous epithelium of the small bowel. The result is transudation of fluid and salts into the intestinal lumen; sometimes, malabsorption of carbohydrates worsens symptoms by causing osmotic diarrhea. Diarrhea is watery. Inflammatory diarrhea (dysentery), with fecal WBCs and RBCs or gross blood, is uncommon. Four categories of viruses cause most gastroenteritis: rotavirus and calicivirus (predominantly the norovirus [formerly Norwalk virus]) cause the majority of viral gastroenteritis, followed by astrovirus and enteric adenovirus.
Rotavirus is the most common cause of sporadic, severe, dehydrating diarrhea in young children (peak incidence, 3 to 15 mo). Rotavirus is highly contagious; most infections occur by the fecal-oral route. Adults may be infected after close contact with an infected infant. The illness in adults is generally mild. Incubation is 1 to 3 days. In temperate climates, most infections occur in the winter. Each year in the US, a wave of rotavirus illness begins in the Southwest in November and ends in the Northeast in March.
Norovirus most commonly infects older children and adults. Infections occur year-round. Norovirus is the principal cause of sporadic viral gastroenteritis in adults and of epidemic viral gastroenteritis in all age groups; large waterborne and food-borne outbreaks occur. Person-to-person transmission also occurs because the virus is highly contagious. Incubation is 24 to 48 h.
Astrovirus can infect people of all ages but usually infects infants and young children. Infection is most common in winter. Transmission is by the fecal-oral route. Incubation is 3 to 4 days.
Adenoviruses are the 4th most common cause of childhood viral gastroenteritis. Infections occur year-round, with a slight increase in summer. Children < 2 yr are primarily affected. Transmission is by the fecal-oral route. Incubation is 3 to 10 days.
In immunocompromised patients, additional viruses (eg, cytomegalovirus, enterovirus) can cause gastroenteritis.
Bacteria:
The bacteria most commonly implicated are
Bacterial gastroenteritis is less common than viral. Bacteria cause gastroenteritis by several mechanisms. Certain species (eg, Vibrio cholerae, enterotoxigenic strains of E. coli) adhere to intestinal mucosa without invading and produce enterotoxins. These toxins impair intestinal absorption and cause secretion of electrolytes and water by stimulating adenylate cyclase, resulting in watery diarrhea. Clostridium difficile produces a similar toxin when overgrowth follows antibiotic use (see Anaerobic Bacteria: Clostridium difficile–Induced Diarrhea).
Some bacteria (eg, Staphylococcus aureus, Bacillus cereus, Clostridium perfringens) produce an exotoxin that is ingested in contaminated food. The exotoxin can cause gastroenteritis without bacterial infection. These toxins generally cause acute nausea, vomiting, and diarrhea within 12 h of ingestion of contaminated food. Symptoms abate within 36 h.
Other bacteria (eg, Shigella, Salmonella, Campylobacter, some E. coli subtypes) invade the mucosa of the small bowel or colon and cause microscopic ulceration, bleeding, exudation of protein-rich fluid, and secretion of electrolytes and water. The invasive process and its results can occur whether or not the organism produces an enterotoxin. The resulting diarrhea contains WBCs and RBCs and sometimes gross blood.
Salmonella and Campylobacter are the most common bacterial causes of diarrheal illness in the US. Both infections are most frequently acquired through undercooked poultry; unpasteurized milk is also a possible source. Campylobacter is occasionally transmitted from dogs or cats with diarrhea. Salmonella can be transmitted by undercooked eggs and by contact with reptiles. Species of Shigella are the 3rd most common bacterial cause of diarrhea in the US and are usually transmitted person to person, although food-borne epidemics occur. Shigella dysenteriae type 1 (not present in the US) produces Shiga toxin, which can cause hemolytic-uremic syndrome (see Thrombocytopenia and Platelet Dysfunction: Thrombotic Thrombocytopenic Purpura (TTP) and Hemolytic-Uremic Syndrome (HUS)).
Several different subtypes of E. coli cause diarrhea. The epidemiology and clinical manifestations vary greatly depending on the subtype: (1) Enterohemorrhagic E. coli is the most clinically significant subtype in the US. It produces Shiga toxin, which causes bloody diarrhea (hemorrhagic colitis). E. coli O157:H7 is the most common strain of this subtype in the US. Undercooked ground beef, unpasteurized milk and juice, and contaminated water are possible sources. Person-to-person transmission is common in the day care setting. Hemolytic-uremic syndrome is a serious complication that develops in 2 to 7% of cases, most commonly among the young and old. (2) Enterotoxigenic E. coli produces two toxins (one similar to cholera toxin) that cause watery diarrhea. This subtype is the most common cause of traveler's diarrhea. (3) Enteropathogenic E. coli causes watery diarrhea. Once a common cause of diarrhea outbreaks in nurseries, this subtype is now rare. (4) Enteroinvasive E. coli causes bloody or nonbloody diarrhea, primarily in the developing world. It is rare in the US.
Several other bacteria cause gastroenteritis, but most are uncommon in the US. Yersinia enterocolitica can cause gastroenteritis or a syndrome that mimics appendicitis. It is transmitted by undercooked pork, unpasteurized milk, or contaminated water. Several Vibrio species (eg, V. parahaemolyticus) cause diarrhea after ingestion of undercooked seafood. V. cholerae sometimes causes severe dehydrating diarrhea in the developing world. Listeria causes food-borne gastroenteritis. Aeromonas is acquired from swimming in or drinking contaminated fresh or brackish water. Plesiomonas shigelloides can cause diarrhea in patients who have eaten raw shellfish or traveled to tropical regions of the developing world.
Parasites:
The parasites most commonly implicated are
Certain intestinal parasites, notably Giardia intestinalis (lamblia—see Intestinal Protozoa: Giardiasis), adhere to or invade the intestinal mucosa, causing nausea, vomiting, diarrhea, and general malaise. Giardiasis occurs in every region of the US and throughout the world. The infection can become chronic and cause a malabsorption syndrome. It is usually acquired via person-to-person transmission (often in day care centers) or from contaminated water.
Cryptosporidium parvum causes watery diarrhea sometimes accompanied by abdominal cramps, nausea, and vomiting. In healthy people, the illness is self-limited, lasting about 2 wk. In immunocompromised patients, illness may be severe, causing substantial electrolyte and fluid loss. Cryptosporidium is usually acquired through contaminated water.
Other parasites that can cause symptoms similar to those of cryptosporidiosis include Cyclospora cayetanensis and, in immunocompromised patients, Cystoisospora (Isospora) belli, and a collection of organisms referred to as microsporidia (eg, Enterocytozoon bieneusi, Encephalitozoon intestinalis). Entamoeba histolytica (amebiasis) is a common cause of subacute bloody diarrhea in the developing world and occasionally occurs in the US.
Symptoms and Signs
The character and severity of symptoms vary. Generally, onset is sudden, with anorexia, nausea, vomiting, borborygmi, abdominal cramps, and diarrhea (with or without blood and mucus). Malaise, myalgias, and prostration may occur. The abdomen may be distended and mildly tender; in severe cases, muscle guarding may be present. Gas-distended intestinal loops may be palpable. Borborygmi are present even without diarrhea (an important differential feature from paralytic ileus). Persistent vomiting and diarrhea can result in intravascular fluid depletion with hypotension and tachycardia. In severe cases, shock, with vascular collapse and oliguric renal failure, occurs.
If vomiting is the main cause of fluid loss, metabolic alkalosis with hypochloremia can occur. If diarrhea is more prominent, acidosis is more likely. Both vomiting and diarrhea can cause hypokalemia. Hyponatremia may develop, particularly if hypotonic fluids are used in replacement therapy.
In viral infections, watery diarrhea is the most common symptom; stools rarely contain mucus or blood. Rotavirus gastroenteritis in infants and young children may last 5 to 7 days. Vomiting occurs in 90% of patients, and fever > 39° C (> 102.2° F) occurs in about 30%. Norovirus typically causes acute onset of vomiting, abdominal cramps, and diarrhea, with symptoms lasting only 1 to 2 days. In children, vomiting is more prominent than diarrhea, whereas in adults, diarrhea usually predominates. Patients may also experience fever, headache, and myalgias. The hallmark of adenovirus gastroenteritis is diarrhea lasting 1 to 2 wk. Affected infants and children may have mild vomiting that typically starts 1 to 2 days after the onset of diarrhea. Low-grade fever occurs in about 50% of patients. Astrovirus causes a syndrome similar to mild rotavirus infection.
Bacteria that cause invasive disease (eg, Shigella, Salmonella) are more likely to result in fever, prostration, and bloody diarrhea. Bacteria that produce an enterotoxin (eg, S. aureus, B. cereus, C. perfringens) usually cause watery diarrhea.
Parasitic infections typically cause subacute or chronic diarrhea. Most cause nonbloody diarrhea; an exception is E. histolytica, which causes amebic dysentery. Fatigue and weight loss are common when diarrhea is persistent.
Diagnosis
Other GI disorders that cause similar symptoms (eg, appendicitis, cholecystitis, ulcerative colitis) must be excluded. Findings suggestive of gastroenteritis include copious, watery diarrhea; ingestion of potentially contaminated food (particularly during a known outbreak), untreated surface water, or a known GI irritant; recent travel; or contact with similarly ill people. E. coli O157:H7–induced diarrhea is notorious for appearing to be a hemorrhagic rather than an infectious process, manifesting as GI bleeding with little or no stool. Hemolytic-uremic syndrome may follow as evidenced by renal failure and hemolytic anemia (see Thrombocytopenia and Platelet Dysfunction: Thrombotic Thrombocytopenic Purpura (TTP) and Hemolytic-Uremic Syndrome (HUS)). Recent oral antibiotic use (within 3 mo) must raise suspicion for C. difficile infection (see Anaerobic Bacteria: Clostridium difficile–Induced Diarrhea).
Stool testing:
If a rectal examination shows occult blood or if watery diarrhea persists > 48 h, stool examination (fecal WBCs, ova, parasites) and culture are indicated. However, for the diagnosis of giardiasis or cryptosporidiosis, stool antigen detection using an enzyme immunoassay has a higher sensitivity. Rotavirus and enteric adenovirus infections can be diagnosed using commercially available rapid assays that detect viral antigen in the stool, but these are usually done only to document an outbreak.
All patients with grossly bloody diarrhea should be tested for E. coli O157:H7, as should patients with nonbloody diarrhea during a known outbreak. Specific cultures must be requested because this organism is not detected on standard stool culture media. Alternatively, a rapid enzyme assay for the detection of Shiga toxin in stool can be done; a positive test indicates infection with E. coli O157:H7 or one of the other serotypes of enterohemorrhagic E. coli. (Note: Shigella species in the US do not produce Shiga toxin.)
Adults with grossly bloody diarrhea should usually have sigmoidoscopy with cultures and biopsy. Appearance of the colonic mucosa may help diagnose amebic dysentery, shigellosis, and E. coli O157:H7 infection, although ulcerative colitis may cause similar lesions. Patients with recent antibiotic use should have a stool assay for C. difficile toxin.
General tests:
Serum electrolytes, BUN, and creatinine should be obtained to evaluate hydration and acid-base status in patients who appear seriously ill. CBC is nonspecific, although eosinophilia may indicate parasitic infection.
Treatment
Supportive treatment is all that is needed for most patients. Bed rest with convenient access to a toilet or bedpan is desirable. Oral glucose-electrolyte solutions, broth, or bouillon may prevent dehydration or treat mild dehydration. Even if vomiting, the patient should take frequent small sips of such fluids: vomiting may abate with volume replacement. For patients with E. coli O157:H7 infection, rehydration with isotonic IV fluids may attenuate the severity of any renal injury should hemolytic-uremic syndrome develop. Children may become dehydrated more quickly and should be given an appropriate rehydration solution (several are available commercially—see also Dehydration and Fluid Therapy in Children: Solutions). Carbonated beverages and sports drinks lack the correct ratio of glucose to Na and thus are not appropriate for children < 5 yr. If the child is breastfed, breastfeeding should continue. If vomiting is protracted or if severe dehydration is prominent, IV replacement of volume and electrolytes is necessary (see Shock and Fluid Resuscitation: Intravenous Fluid Resuscitation).
When the patient can tolerate fluids without vomiting and the appetite has begun to return, food may be gradually restarted. There is no demonstrated benefit from restriction to bland food (eg, cereal, gelatin, bananas, toast). Some patients have temporary lactose intolerance.
Antidiarrheal agents are safe for patients > 5 yr with watery diarrhea (as shown by heme-negative stool). However, antidiarrheals may cause deterioration of patients with C. difficile or E. coli O157:H7 infection and thus should not be given to any patient with recent antibiotic use or heme-positive stool, pending specific diagnosis. Effective antidiarrheals include loperamide 4 mg po initially, followed by 2 mg po for each subsequent episode of diarrhea (maximum of 6 doses/day or 16 mg/day), or diphenoxylate 2.5 to 5 mg tid or qid in tablet or liquid form.
If vomiting is severe and a surgical condition has been excluded, an antiemetic may be beneficial. Agents useful in adults include prochlorperazine 5 to 10 mg IV tid or qid, or 25 mg per rectum bid; and promethazine 12.5 to 25 mg IM tid or qid, or 25 to 50 mg per rectum qid. These drugs are usually avoided in children because of lack of demonstrated efficacy and the high incidence of dystonic reactions.
Antimicrobials:
Empiric antibiotics are generally not recommended except for certain cases of traveler's diarrhea or when suspicion of Shigella or Campylobacter infection is high (eg, contact with a known case). Otherwise, antibiotics should not be given until stool culture results are known, particularly in children, who have a higher rate of infection with E. coli O157:H7 (antibiotics increase the risk of hemolytic-uremic syndrome in patients infected with E. coli O157:H7).
In proven bacterial gastroenteritis, antibiotics are not always required. They do not help with Salmonella and prolong the duration of shedding in the stool. Exceptions include immunocompromised patients, neonates, and patients with Salmonella bacteremia. Antibiotics are also ineffective against toxic gastroenteritis (eg, S. aureus, B. cereus, C. perfringens). Indiscriminate use of antibiotics fosters the emergence of drug-resistant organisms. However, certain infections do require antibiotics (see Table 1: Gastroenteritis: Selected Oral Antibiotics for Infectious Gastroenteritis* ).
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Table 1
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| Selected Oral Antibiotics for Infectious Gastroenteritis* |
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Organism
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Antibiotic
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Adult Dosage
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Pediatric Dosage
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Vibrio cholerae
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Ciprofloxacin
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1 g once
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NA
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Doxycycline†
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300 mg single dose
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6 mg/kg x 1 dose
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TMP‑SMX
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1 DS tablet bid for 3 days
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4–6 mg‡/kg bid for 5 days
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Clostridium difficile
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Metronidazole
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250 mg qid or 500 mg tid for 10 days
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7.5 mg/kg qid for 10 days
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Vancomycin (if fails, metronidazole)
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125–250 mg qid for 10 days
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10 mg/kg qid for 10 days
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Shigella
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Ciprofloxacin
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500 mg po bid for 5 days
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NA
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TMP‑SMX
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1 DS tablet bid
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4–6 mg‡/kg bid for 5 days
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Giardia intestinalis (lamblia)
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Metronidazole
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250 mg tid for 5 days
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5 mg/kg tid for 5 days (maximum 750 mg/day)
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Nitazoxanide
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500 mg bid for 3 days
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1–3 yr: 100 mg bid for 3 days
4–11 yr: 200 mg bid for 3 days
≥ 12 yr: 500 mg bid for 3 days
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Entamoeba histolytica
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Metronidazole§
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750 mg tid for 5–10 days
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12–16 mg/kg tid for 10 days (maximum 750 mg/day)
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Campylobacter jejuni
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Ciprofloxacin
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500 mg bid for 5 days
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NA
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Azithromycin
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500 mg once/day for 3 days
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10 mg/kg once/day for 3 days
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*Antibiotics are not indicated in most cases but may be used supportively with IV fluids to treat infections caused by specific organisms.
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†This drug should not be given to children aged < 8 yr or to pregnant women.
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‡Dose is based on trimethoprim component.
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§Treatment should be followed by iodoquinol 10–13 mg/kg tid for 20 days or paromomycin 500 mg po tid for 7 days.
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DS = double-strength; NA = not applicable; TMP/SMX = trimethoprim/sulfamethoxazole.
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The use of probiotics, such as lactobacillus, is generally safe and may have some benefit in relieving symptoms. They can be given in the form of yogurt with active cultures.
For cryptosporidiosis, nitazoxanide may be helpful in immuno competent patients. The dose is 100 mg po bid for children 1 to 3 yr, 200 mg po bid for children 4 to 11 yr, and 500 mg po bid for children ≥ 12 yr and adults.
Prevention
A new oral pentavalent rotavirus vaccine is available that is safe and effective against the majority of strains responsible for disease. This vaccine is now part of the recommended infant vaccination schedule and is given at 2, 4, and 6 mo of age (see Table 12: Approach to the Care of Normal Infants and Children: Recommended Immunization Schedule for Ages 0–6 yr).
Prevention of infection is complicated by the frequency of asymptomatic infection and the ease with which many agents, particularly viruses, are transmitted from person to person. In general, proper procedures for handling and preparing food must be followed. Travelers (see Gastroenteritis: Traveler's Diarrhea) must avoid potentially contaminated food and drink.
Breastfeeding affords some protection to neonates and infants. Caregivers should wash their hands thoroughly with soap and water after changing diapers, and diaper-changing areas should be disinfected with a freshly prepared solution of 1:64 household bleach (¼ cup diluted in 1 gallon of water). Children with diarrhea should be excluded from child care facilities for the duration of symptoms. Children infected with enterohemorrhagic E. coli or Shigella should also have two negative stool cultures before readmission to the facility.
Last full review/revision September 2007 by Thomas G. Boyce, MD, MPH
Content last modified September 2007
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