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Michael A. Davis, MD


Acute gastroenteritis is defined as diarrheal disease of rapid onset, often with nausea, vomiting, fever, or abdominal pain. It occurs an average of 1.3-2.3 times per year between the ages of 0 and 5 years. Rates among children in child care centers are three times higher. Most episodes of acute gastroenteritis will resolve within 3 to 7 days.


Gastroenteritis in children is caused by viral, bacterial, and parasitic organisms, although the vast majority of cases are viral or bacterial in origin. Twenty five percent of cases may be reported as having "no pathogen," depending on the quality of the laboratory techniques used.

Oral ingestion is the primary route of infection, although rotavirus is transmitted by respiratory or mucous membrane contact as well.

Viral Gastroenteritis

All of the viruses produce watery diarrhea often accompanied by vomiting and fever, usually not associated with blood or leukocytes in the stool or with prominent cramping.

Rotavirus is the predominant viral cause of dehydrating diarrhea. Rotaviral infections tend to produce severe diarrhea, causing up to 70% of episodes in children under 2 years of age who require hospitalization. Rotavirus infection tends to occur in the fall in the southwest of the US, then sweeping progressively eastward, reaching the northeast by late winter and spring.

Norwalk viruses are the major cause of large epidemics of acute nonbacterial gastroenteritis. In schools, camps, nursing homes, cruise ships, and restaurants.

Enteric adenovirus is the third most common organism isolated in infantile diarrhea.

Bacterial Gastroenteritis

The bacterial diarrheas work through the elaboration of toxin (enterotoxigenic pathogens) or through invasion and inflammation of the mucosa (invasive pathogens).

Secretory diarrheas are modulated through an enterotoxin, and the patient does not have systemic symptoms (fever, myalgias) or signs of local irritation of the bowel (tenesmus), or evidence of gut inflammation in the stool (white or red blood cells). The diarrhea is watery, often is large in volume, and often associated with nausea and vomiting.

Invasive diarrhea is caused by bacterial enteropathogens, and is accompanied by systemic signs, such as fever, myalgias, arthralgias, irritability, and loss of appetite. Cramps and abdominal pain are prominent. The diarrhea consists of the frequent passing of small amounts of "mucousy" stool. Stool examination reveals leukocytes, red blood cells, and often gross blood.

The same organisms that typically cause an invasive or inflammatory pattern of illness also may cause a secretory or viral pattern.

Acute Diarrhea Patterns and Associated Pathogens



Characterized by watery diarrhea and absence of fecal leukocytes

Characterized by dysentery (ie, symptoms and bloody stools), fecal leukocytes, and erythrocytes

Food poisoning (toxigenic)

Staphylococcus aureus

Bacillus cereus

Clostridium perfringens


Invasive E coli




Escherichia coli

Vibrio cholera

Giardia lamblia



Norwalk-like virus

C difficile

Entameba histolytica

General Approach to the Patient with Gastroenteritis

Rapidly determining and managing the fluid losses, dehydration and electrolyte abnormalities is significantly more important than ascertaining the specific microbiologic cause.

History should include questions regarding recent antibiotic use, underlying diseases, other illnesses in the family, travel, untreated water, raw shellfish, attendance at a child care center, and foods eaten recently.


Clinical Evaluation and Treatment of Acute Diarrhea

Step One--Assess child for degree of dehydration

No dehydration

Continue oral hydration and feeding

Some/severe dehydration--------->

Initiate rehydration by oral route (intravenous for severely dehydrated patients)

Step Two--Assess Clinical History for Etiologic Clues

Etiologic Clue

Etiology Suggested

Fever, crampy abdominal pain, tenesmus

Inflammatory colitis or ileitis

History of bloody stool

Shigella, enteroinvasive EC, amebiasis, other bacterial causes

Fever and abdominal pain and like appendicitis

Yersinia enterocolitis

Current or previous antibiotic use

Antibiotic-associated enteritis or pseudomembranous colitis

Multiple cases and common food source

Incubation <6 hours: Staphylococcus aureus, Bacillus cereus

Incubation >6 hours: Clostridium perfringens

Ingestion of inadequately cooked seafood

Vibrio sp

Recent measles, severe malnutrition, AIDS, other causes of immunosuppression

Bacterial (Salmonella), viral (rotavirus), or parasitic (isosporiasis, Cryptosporidium)

Step Three--Examine Stool:

Indicated for:


Etiology Suggested:

Visual examination of specimen

All patients

Gross blood

Dysentery, colitis, invasive organism


examination for

white/red blood cells

Patients who have had diarrhea >3 days, fever, blood in stool, weight loss beyond fluid deficit

Red cells and leukocytes

Red cells without leukocytes

Shigella, enterohemorrhagic EC, enteroinvasive EC, Campylobacter, Clostridium, E histolytica

Parasitic examination (wet mount, acid-fast staining, or concentration)

Diarrhea >10 days


Giardia, Amoeba, Cryptosporidium, Isospora, Strongyloides

Clostridium difficile toxin

Especially patients taking antibiotics


C difficile colitis




Assessment of Diarrheal Dehydration

Clinical Finding


(10-40 mL/ kg)


(50-90 mL/kg)


(100-130 mL/ kg)









Deeply sunken

Mucous membrane



Very dry

Tears when crying









++++ or unresponsive

Skin turgor (capillary refill)


Reduced (<1 sec)

Very reduced (2-3 sec)




Severely depressed





Feeble or absent

Pulse rate



Very rapid

Blood pressure



Low or absent

Fluid Therapy

Mild-to-moderate dehydration

Oral rehydration therapy (ORT) is the preferred method. ORT is a glucose-electrolyte solution.

Mildly or moderately dehydrated children should receive ORT at 50 mL/kg (mild dehydration) or 100 mL/kg (moderate dehydration) over a 4-hour period. Replacement of stool losses (at 10 mL/kg for each stool) and of emesis (estimated volume) will require adding appropriate amounts of solution to the total.

If all but sips of fluid are vomited, oral hydration can be achieved by administering a teaspoonful of solution every 2 to 5 minutes.

Use of cola, fruit juice and sports beverages are not recommended; their electrolyte content is inappropriate, and they contain too much carbohydrate.

Prevention of Dehydration. Children who have diarrhea, but not dehydrated, may be given glucose-electrolyte solution in addition to their regular diets to replace stool losses; however, special solutions are not necessary as long as the well-hydrated child can consume an age-appropriate diet and is encouraged to drink more than the usual amounts of the normal fluids in his diet.

Severely dehydrated children who are in a state of shock must receive immediate and aggressive intravenous (IV) therapy. When the patient is stable, hydration may be continued orally.

Intravenous Rehydration

When intravenous rehydration is required, it should begin with an isotonic solution (normal saline, lactated Ringer). Severe dehydration clinically is associated with a loss of 10-12% of body weight in fluids and electrolytes (100 to 120 mL/kg); therefore, this amount plus whatever additional losses occur should be infused in no more than 6 hours in infants, and even more rapidly in children older than 1 year.

Infusion rates of up to 100 mL/min are appropriate in older children. Infusion rates of 40 mL/kg are given over the first 30 minutes, with the remainder of the deficit (70 mL/kg) over the next 2.5 hours, accompanied by clinical observation until a strong radial pulse is restored and the calculated fluid loss replenished.

For infants, correction should be slower, with infusion rates no more than 30 mL/kg over the first hour and the remaining 70 mL/kg over 5 hours to avoid rapid extracellular to intracellular shifts of fluid and electrolytes and subsequent convulsions.

Subsequent maintenance fluids should be given orally. Oral fluids should be initiated as soon as the patient can drink. They should be given simultaneously with intravenous fluids until the total fluids administered have replenished the calculated deficit, after which the intravenous line can be discontinued.

Antibiotic Therapy

The effectiveness of antimicrobial therapy is well established in shigellosis. Shigella is the classic cause of bacterial dysentery and is the second most commonly identified bacterial pathogen in diarrhea between the ages of 6 months and 10 years in the US.

It causes an initial brief period (1 to 2 days) of watery diarrhea and then it invades the colonic epithelium, causing frequent bowel movements with mucus and gross blood. Treatment usually consists of ceftriaxone or cefixime.


Children who have diarrhea and are not dehydrated should continue to be fed age-appropriate diets. Children who require rehydration should be fed age-appropriate diets as soon as they have been rehydrated. Early feeding of a regular diet reduces the duration of diarrhea.

Fatty foods and foods high in simple sugars, such as sweetened tea, juices, and soft drinks should be avoided. Well-tolerated foods include complex carbohydrates (rice, wheat, potatoes, bread, and cereals), lean meats, yogurt, fruits, and vegetables. The BRAT diet (bananas, rice, applesauce, toast) does not supply optimal nutrition.

Introducing the child's regular form of milk early in the course of therapy is recommended. Although diarrhea often is associated with a reduction in intestinal lactase, this change is not significant in 80% of pediatric patients. If lactose intolerance becomes apparent, a lactose-free preparation may be substituted.

Antidiarrheal Compounds (eg, loperamide, diphenoxylate, bismuth compounds, Kaopectate) should not be used to treat acute diarrhea.

Laboratory Examinations

Most noninflammatory diarrheal illnesses respond in 3 to 5 days to simple rehydration therapy and dietary management alone, obviating the need for initial laboratory evaluations. The presence of blood in the stool, fever, or persistence of the diarrhea for more than 3 days may trigger a laboratory pursuit of an etiologic agent.

Microscopic Stool Examination. If erythrocytes and white blood cells are present, particularly in the setting of fever, a bacterial pathogen (Campylobacter, Yersinia, Salmonella, Shigella) should be suspected. Many red blood cells in the absence of white blood cells suggests the presence of Entamoeba.

Stool culture should be reserved for individuals whose diarrhea has not responded to fluid and feeding and for those who have signs of inflammatory disease (fever, myalgias) and the presence of leukocytes or red blood cells in the stool.


Clinical Evaluation and Treatment of Persistent Diarrhea-lasting longer than 14 Days


Assess child for degree of dehydration ------------> Appropriate rehydration

Step–Two. Assess Etiologic Clues

Etiologic Clue

Etiology Suggested

Bloody stool

Invasive organism, particularly Shigella and Entameba histolytica

Malnutrition (inadequate weight for age)

Inadequate diet, decreased resistance

Dietary changes, especially addition of milk or formula

Possible milk or protein hypersensitivity

Problems following milk ingestion

Lactose malabsorption

Antibiotic treatment

Antibiotic-associated enterocolitis or resistant organism

Step–Three. Stool Examination



Etiology Suggested

Visual examination

Bloody stool

Invasive organism

Microscopic stool exam, including search for ova, parasites, and Cryptosporidium

Red and white blood cells

E histolytica cysts

Giardia, E histolytica trophozoites

Shigella, other invasive organism

Etiologic role unclear

Etiologic role more likely; specific treatment indicated

Stool pH, reducing substances

pH <5.5 and ++ reducing substances

Lactose or other carbohydrate malabsorption.

Stool culture and sensitivity

Pathogens present

Etiology and antibiotic treatment